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THE LUNAR CRATER PLTJTO. Sib —The results of observation of the floor of the lunar'crater Pinto which have appeared elsewhere see Slud,*t. April, 187", p. 101 belugof Interest in connection with questions now agitated relative to changes on the moon's surface, the following sunimaiy of further observations during the April lunation may not be uninteresting to your numerous readers

The observations were made by Mr. Gledhill; ol Jir. Crowley s Observatory, Halifax; Mr. Pratt, of Bricbton, and Mr. Elgcr, of Bedford. Sixteen only of the 35 known spots were seer.; they are numbered 1, 1. 4, 5 6 9 II 14.10,17, 22, 24, 25. 30, 32, and S3, but Mr. Gledhill detected an unrecorded one, which is numbered 35. Of these the following were seen by the three observers-vii., Nos. 1, 3, 4,5, 16, audi, ; no

doubt*, therefore, can be cast on their visibility duriue April. No. 14 was observed by Messrs. Elgcrnud Pratt ou seven occasions, but missed by Mr.Gledhill Ibo spots seen by Mr. Gledhill only were Boa. 0,0.11, W. 32 SB and 35; by Mr. Elgor only, Nos 24 and 2.), and by Sir. Pratt only, No. 22, Taking spot No. 1 (the most constantly seen) as the standard = l'OOi, the degrees

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of visibility are as under
Spot 1 4 3 17

Vis. 1-000 1000 -895 -780
Spot SO 8 11 24

"Vis. -210 '105 -105 -105

The number of observations of tho spots between April, 1800, and March, 1870, inclusive, amounted to 771 in 108 series ; those during April amounted to 118 in 19series. These numbers give" for the avornge number of spots visible on any one evening. The curves of visibility of 14 spots have been projected for the 121unations ending March, 1870, and of these 14 spots S were not seen on any one of the 19 sets of observations— viz., Nos. 2, 7. 10,13, and 19.

The intermittent character of the above unrecorded spots in April Is beconiiug more and more manifest. No. 2 has been observed 7 times only between Aunist, 1861, and March, 1S70, inclusive. No. 7invislblcin June and July 1869, and in February, March and April, 1S70. No. 10 invisible between Oct, 1SC9 and January, 1S70. inclusive. No. 13 seen on 28 occasions during the past year, invisible in April, 1870. The same may be snld of No. 19, it having been seen 27 limes during the last year, and invisible In April, 1870. No. 22 may be included in the same class, for although It was recorded on every line evening iu August and September. 1869, it Is now but rarely seen. The variationsln the visibility of the spots more constantly seen lead to the same conclusion—viz., that their visibility is also intermittent. Itmust, however, be borne in mind that the visibility of Bpots very rarely seen, once or twice for example, in the course of a lunation, may depend upon the slate of the earth's atmosphere; it is, nevertheless, difficult to conceivethat the earth's atmosphere is capable of obscuring spots for months together, while others quite us difficult of perception are visible.

An Increased accuracy is attainable by the number of observers being augmented, for, as iu all observation of the kind, eirors that necessarily affect the lew are eliminated iu tho case of the greater number, so errors arising in the visibility of the spots from differences in the state of the earth's atmosphere at distant stations, and also iu cousequence of the overlooking of minute objects by one observer which are distinctly visible to auother, disappear to a great extent, when the observers are numerous, the greater weight being accorded to the visibility of those spots that are seen bv the greatest number of observers. W. It. Birt, Cynthia Villa, Walthamstow.

"OTTER" FOB LIFE BOAT SERVICE.

Sir,—Amongst the requirements for life boat service. It has been held to be a desideratum to And means for depositing an anchor on emergencies at a distance from the chore convenient for using a block and double rope attached thereto, to enable those on shore to haul off a boat through surf, and to the various schemes for this purpose, I wish to offer an additional one. There is a certain fishing implement of the pot hunting or poaching class, by which a line can be carried out (with hooks, &c.) called an "Otter." the construction and action being this: A flat board Is (by being weighted with lead) made to swim edgeways; to It Is attached a loop similar to the bollyband of a boy's kite; to the loop is fastened the fishing line in a certain position upon launching and paying out the line. The " Otter" leaves tho shore in an oblique direction, and is hauled along to the extent of the Hue. On this principle it is proposed to construct a machine of the following description. Fig. 1, A IS O is an anchor, of which the ring is at A, and single flake BO attached to aflat frame built up of board and cork. A B I>C, the upper portion of which, C E V 1>. is removeable, sliding out from the lower portion backwards, having line and ring fastened to it L E, the whole ol such buoyauey as to float the entire machine level atabout the line E F; G K H loop or bollyband, to which, in proper position for effecting the o"blique motion in hauling off, are fastened a block and double line rove there through I K. A stronger connection is to be made between the block K and anchor ring A, by line or rope A It. In use, the upper sliding portion of the frame is to be fastened by a line Jrd the strength of the line L E, also the bollyband is to be so contrived that the sliding out ol the'upper part of the frame shall let it fall loose. The action Is presumed to be this (i.r., supposing this saltwater "otter" behaves equally well with its fresh water progenitor, aud there seems no reason to suppose it otherwise), that upon launching, the machine drawn by double rope It I, will proceed to sea, and gain oiling according to length of rope K 1, trailing behind It the line L K. On acquiring proper oiling and position, the travelling line is to be jerked so as to break the fastening Jrd its strength, aud pull out the upper sliding portion of the trams, which is to be hauled ashore, and also

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direction required, and, finally, the double rope bo in position to be efficiently used for hauling off .the life boat. Fig. 2 shows a sketch or the position of the "Otter" floating, seen from above. A B shore line. L E trailing line, by pulling which the upper frnme is drawn away. It 1 double rope to shore. The machine to be fitted on a Bmall carriage with long polo aud launching ropes, as in life boat carriages. Two wheels only are wanted lor carriage. The whole affair might weigh from 4cwt. to 6cwt., including carriage. Suffolk Amateur.

. P.S.—I may just add an idea about self-righting life boats. The principle is as old at least as any grown man who, as a s mall boy, put a leaden keel to his play boat, and deduced from the observation that the form of the upper works has nothing to do with the matter, but that it depends altogether upon the centre of gravity or otherwise on weight below overbalancing weight above.

FAIRY WHEELS.

Sir,—1 enclose you the only one I have left of these ancient stone discs, trusting you, or some of your correspondents, may be able to throw some light as to the purpose for which so much trouble has been bestowed on them ; they are only found iu one field on the farm, but were much more plentiful forty yearn ago than now; at that time, we used to suppose they had been made by children, as wheels for toy carts. One of my ploughboys, about this time last year, picked up about a dozen of them; ho brought four or five home, throwing the others away. The one I forward is much the smallest, aud the thickest. I am sorry to Bay the others are all lost; the one I Bend is much more carefully made than any of the others were. Noue of them were the same size ©r thickness; some of them showed the Baw marks very distinctly; they had been Bawu out of cylinders of different sizes; the

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holes through have been bored after each disc was cut off, sorne of them quite oblique, but all rimmed from inch side as this is; they were all thick in the middle, -hough none were so much rounded off as the one Bide of this, neither had any of them the perfectly flat side you see in this one. I do not kuow of any stone iu this neighbourhood that at all resembles this they are made of. I recollect scciug them with serrated edges, ae though the notches had been cut with a flle; I also believe I saw some of the same dug up at Uriconium (Uttoxeter), about two miles from here. From the careless manner with which the holes were drilled through them, I sho'.il! say it has been for the purpose of threading them on a string; the one I send has evidently lain in the grouud very many years, by tho gravel being so (irmly attached to it. The opinion of some of your readers' on it will oblige.

I have seen some quite twice as large, aud above ball as thick. . A Subscriber.

SILVKRLNG SPECULA.

Sir,—Allhough I am no chemist, and am therefore unprepared to account for some of the failures which may happen in the above art, my own repeated failures have, nevertheless, taught me a few lesBous, and have led me to the opinion that nine cases out of ten of these failures occur chiefly through want ol sufficient care in cleaning the glass surface intended to be silvered; and although the few hints I have to offer do not perhaps apply entire to the " Rochelle salt " process, your correspondents, M. Gray, p. 163,and " Interested." p. 191, may, I hope, find them useful as regards the washing. . .

The following particulars as to chemicals refer to

Liebig's process as given by Browning, this being the only process I have attempted. The proper cleansiug of the glass is doubtless equally ns necessary in both processes. In the first place, distilled waler, that is, chemically pure, must be used, I have'not tried rain water, but should think it would succeed when collected in clean vessels and properly subsided. 2nd. TbechemicalB shonld,beobtained of areliablechcmlst nitrate of silver is, 1 bclicvo, ordinarily good. The potash must be pure by alcohol. The ammonia should be the strongest obtainable. In cleaning the glass, the strougest nitric acid should be used ; If good;it gives out copious fumes, and may be easily known by the prompt manner in which it attacks the eyes and nose. First place the mirror face upwards (previously cemented to the wooden block) in a large dish, pour the nitric acid on it, and gently rub the glass all over its surface and Bides with a pad of medicated wool plugged into a glass tube; then rinse the wool in common water, and repeatedly wash off the excess of acid, taking care to give the same attention to the sides ;as to the surface; this done, do not touch the glass with the fingers, but take hold of the block to which it is attached, and hold it under ruuningwater from a tap for about five minutes, continually moving It, that the jet may play freely over the back, the sides, and lastly tho surface; then examine the surface of the glass, aud if the water baa a tendency to run away from the edge of the disc, as If greasy, the process must be repated until all greasiuess disappears. The glass is then laid iu a sloping position, and another woollen brush used to cleanse it with distilled water; this brush should not be touched with anything but distilled water, into which it is now dipped, and the glass repeatedly rinsed all over with it, until any apparent greasiuess which the first contact with distilled water may occasion entirely disappears.

The glass is now ready for silvering, and is laid wet, face downwards, Iu a dish containing a little pure alcohol (just sufficient to touch tho entire face of the glass) until the silvering bath is quite ready. Caution must be observed throughout the entire process not to touch the face of tho glass once with the Angers if possible. One or two particulars as to tho silvering fluid may be serviceable. II the process la conducted in cold weather, It is advisable to warm the solution slightly, this may bo done when tho distilled water is added, by warming somoof it in a clean cup placid in a basiu of hot water for a few minutes; this helps to subside the precipitale more quickly, and renders tho fluid transparent before pouring into UiesilveringdiBh, which Is necessary to prevent spots in the silver film. Another essential item is to completely dissolve the milk sugar; this caii scarcely be doue in cold water, but is quickly done by warming in a cup placed in hot waler. as before. Tho slight warmth given to the silvering fluid has also the important advantage of giving a harder and more adhesive film.

In placing the mirror face downwards in the bath, care sho.ild be taken to enclose no bubbles under Its surface ; one side should be lowered first, and then the entire surface brought gradually level; it should not sink too deep into rhe fluid ; the nearer the surface the better, providing the face is fairly immersed. When the film iB complete, it Is removed and immediately washed under the tap for five minutes as before, then stand the mirror on edge In a dish, and gently rinse with distilled water either with the woollen brush or with a piece of soft clean sponge ; when it is thoroughly dry, polish first with clean wash leather, then with rouged leather.

In answer to Mr. Gray's query, tho proper aperture of a diagonal plane fora Newtonian may becstimatod

at Jib. or -th tho aperture of the speculum, whatever

its size, providing the focus of speculum is thrown just outside the great tube, as is usual. ,„„.„„

As the" Harmonious Blacksmith "and "F.RA..S. have associated my name with tho subject of "pls"nlBcd mirrors," I mustadmitmy entlreignornnceof the process, and as to the advantago of platina over silver in point of reflecting power, I should have serious doubts, and as to the "baking process" for such sensitive thloesas specula I should have very little doubt, and should require positive evidence to convince me that it could be anything else than a failure. W Purkiss, 9, Cumberland-street, ltomau-rond, N.

EXPANDING DRILLS FOR MINING PURPOSES. Sir —In the issue of the English Mechanic of the Oth inst., 1 find you have inserted a short paragraph (taken from the Minim/ Journal) relating to au invention by Mr. E. P. Gleason, of an expanding drill for boring purposes, by means of which a chamber or cavity can be made at the bottom of a drilled hole for the reception of the blasting powder, and by which means a vast additional force can bo obtained for disintegrating and blowing up the rock. Now, It so happens that I myself iuvouted a similar drill borer about seven years ago, a description of which, at the time, appeared in the North Wales Chronicle, which was extracted the next week after its appearanco in the columns of the Mining Journal. Judging from it In the note In question, it would appear that Mr Gleasou's invention and my own are precisely similar in principle, and pretty nearly so in the carryin" out of it iu detail, which certainly is a somewhat strange coincidence. In my Invention, the cutting part is composed of two cast steel blades, which are inserted about 4in. above the bottom of the irou rod, the blades being screwed in so as to be the more easily taken out or replaced when they require sharpening. The chamber at the bottom, has a diameter of sjin. (the hole made by the common borer being ljin. iu diam ), and as the perpendicular hole is coutiuued bv the operation 4in. or 5ln. below the chamber, the latter can te extended to any reasonable depth. My expanding drill-borer has beeu successfully tested In several slate quarries in the neighbourhood, and notably so nt the Hcndre Ddu slate quarry, near this town. Sir Edward Poore was at that time the managing director of the said quarry, and was assisted X>y Mr. W. Jones, a thoroughly practical miner. VVo experimented on a largo piece of rock, and a holo was drilled to the depth of 11+ft. The charge was 101b. of rock powder, and above 500 tons of rock were Mown up, the explosion bein^ a tremendous one, and the rock was shattered in all directions. This result was considered to be most satisfactory by all who were present and witnessed it, as thequantity of slate rock obtained by the powder charge of 10lb. was equal to what was usually obtained in the quarry by the expenditure of 1001b., to fray nothing of ttho great expense saved in the matter of labour. From this you will perceive that Mr. Gleason's invention has oeen long since anticipated by myself. In an obscuro town in North Wales. As a contributor to your valuable paper for the last four years, 1 trust you will do mo the Justice to admit this letter in the next number of the English Mechanic.

John Williams (Joan Madoc), shipgmith, Port Modoc, Carnarvonshire,

"C. R. 0., HANTS," ON SEVERAL MATTERS.

Sir.—" Salopian," on page 190, wishes to know how it is that the circumference of the earth at the Equator is greater than the circumference drawn through ihe poles ; he quotes the difference at 25 miles. A moment's reflection will show him what a mere trifle this ia when we take into consideration the vast dimensions of our globe; I question very much if many billiard balls—perfect as they apparently ore— can boast such a Blight departure from the form of a true sphere. I believe myself that centrifugal force certainly causes what "Salopian" refers to, and that its power, exerted throughout the whole mass of the revolving earth, is just so much, ami no more than sufficient to occasion this swelling out at the Equator. 'J his opinion will, I think, in no way stultify the arguments in my previous letter on the earth's rotation.

Touching this same subject, I must confess that it was with the greatest possible gratification I read Mr. Proctor's kindly-worded comment on my letter; encouragement from that gentleman is worth something. Will ho allow me, in my turn, topreseutmy compliments to him, and trust we may often have the pleasure of reading his most valuable contributions to our Mechanic?

An apology is due to " An Adept,** inasmuch that I have delayed so long acknowledging his kindness in replying to my question on the construction of .Hourdon pipes. The fact is, |I have been waiting, unwilling to bother him during his unfortunately still continued indisposition, but seeing that other correspondents arc not so considerate, and fearing that he may perhaps deem me ungrateful, which I assuro him is very far from the case, 1 can hold out no longer. The plan that gentleman suggested—viz., to place the

fiipes in two rows, would have been obvious to me, md the special circumstances of my case admitted of it; I worded my letter badly, and "An Adept" naturally thinks depth is no object. What I wish to ascertain is, could a pretty good quality of tone be obtained from pipes constructed with a much greater depth than usual in proportion to their width? For instauco, could CCC be made 4jtn. by 8in. internal measurement? The double row plan I wish to avoid if possible, for many reasons. I trust our correspondent may soon be restored to perfect health.

What in the name of all that is polite and charitable, can "Eleve"—himself, I presume, a musical manmean by putting such a questiou as this to your correspondents? '■ Tell me why a double manual instrument should be preferred to a single, if the single set of keys can be made to do tho work as well?" Is this from Lord Dundreary, or what? One might just as sensibly put tho query, why eat bread and butter when bread alone could probably do its work just as well in nourishing the animal system? Amateurs, and intending purchasers, make no mistake, you will get incalculably more real and lasting satisfaction from a double manual than a Binglc; ask any organist. Chorus and fugue playing may be performed very well on a single manual, but how about " He was despised," from tho "Messiah," or, "O, rest in the Lord," from "Elijah," and the hundred and one other pieces depending for their very life and soul on a clear, distinct, and individual melody? To my mind the harmonium, especially, requires two manuals, from the very nature of its tone, whose most marked characteristics are, in a good instrument, an apt capability for producing grand and majestic harmonies, but there always seems to be a lalling off when anything of a melodic character Is attempted, hence the value of two rows of keyB. I on my side appeal to the " Harmonious Blacksmith" for his verdict; his writings, which every ono must eDjoy, speak well for the value of any opinion he may offer.

The subject of harmoniums naturally associates itself with Mr. Hermann Smith, and if you, Sir, have been instrumental in bringing him back among us, you have my most cordial thanks. Let any one peruse Mr. Smith's chapters on the harmonium, from their commencement, and see what ground he has broken up, before untrodden, and what vistas of thought, apart from the mere dry details of construction, he has opened out to a thinking mind. A painstaking and conscientious writer, Sir, and a comrade we cannot afford to lose from our ranks.

I am delighted to see such a long list of extracts from various correspondents relative to tho success of our paper. You merit our very warmest praUe and congratulation. There can be no doubt that to your own able and talented leadership all the increasing excellence of this periodical is due; you have indeed reason to be proud, Sir, of your achievement, for the press has certainly never before sent, through the length and breadth of the land, such a mass of useful lioterature at such a nominal price-no, nor at any price. My best wishes are yours. C. R. O.

TURNING.—BORING CYLINDERS.

Sir.—Ou page 18'.", Query 3""1, a question is naked relative to turning, which, with your permission, I will answer.

I imagine tho cause of " Amateur Turner's " failure is the speed at which he drives his work, as no tool will stand, even against softwood, if it Is driven at too groat a rate. The best way that I find to take the scale off cast iron is take a moderately deep cut at first, so as to get underneath the scale, and the piiut of the

tool buried in the clean metal under it; but some castings are so uncommonly hard that no tool will touch them, especially those cast in the country, and it is impossible to do anything with them. If •' Amateur Turner " will tell me the diameter of his work, I shall be able to inform hira how many revolution* the mandrel shoufd make in one miuute to give tho proper cutting speed.

As to the second part of the question; a cylinder may be bored very fairly by setting it up on the faceplate of the lathe, if a largo one (a small one may be soldered ou to a brass chuck or held iu tho cup chuck) by one flange, and running an inside tool through it by means of the upper slide of the rest, taking care to get the slide set perfectly parallel to the axis of the mandrel, and frequent use of the callipers is the only means ©f ascertaining this. But there is another plan which I think is superior to the above (If " Amateur Turner" is the happy possessor of a screw cutting lathe), and that is to sot up the cylinder to be bored ou tho saddle of the slide rest (the rest itself removed) and Axing a cutter bar with projecting cutter between the centres of the lathe and causing it Che cutter) to traverse through the cylinder by the sliding of the saddle; this, if properly managed caunot fail to produce a truly cylindrical bore. Cylinder covers are turned by chucking them in a wood chuck, and turning one side and edge, thenreverse them to turn the otherstde. And now, having answered the above questions, allow me to ask one of my fellow-readers—viz , What is the construction of HoltzapflVd's screw cutting tool-holder or cutter bar for V or square threads, by which the tool may be adjusted to the exact rako of tho thread. A drawing to scale would oblige. G. W. A.

COLOUR BLINDNESS AND ASTRONOMICAL OBSERVATION.

Sir,—The readers of the English Mechanic have recently been entertained with a rather acrimonious discussion on the subject of tho colour of tho belts of Jupiter by two of its most valued contributors. Iu one of the letters I perceive that one of tho disputants admits that an eyo "successful iu detecting minute forms of detail may altogether fail to nut leu gradations of colour."

This fact has been considerably enlarged upon by "Omicrou" in the series of articles on Colour-blindness, and It appears to me that there is clear evidence in the columns of the Mechanic of a case of colourblindness, although there is not, perhaps, sufficient evidence to determine which one of your correspondents is affected with abnormal vision.

Mr. Browning says of the drawing of Jupiter that appeared in tho Student that " tho yellow and red are too bright, and the ashy blue or gray far too dark." Mr. Denning says that tho colour of Jupiter, as seen in his telescope, was very apparent, but not so dark as shown in the print. Mr. Giover says that the colours in the drawing are certainly too vivid. In opposition to these remarks, Mr. Purkias holds the opinion that Jupiter appeared even more vivid than tho engraving in the Stmhint. Perhaps these conflicting remarks are hardly sufficient to warrant the chargo of colourblindness, as "Omicrou" has employed the expression, for the discrepancy in tho description is one rather of quantity than quality. But us the term appears to be applied to every degree of deficiency of appreciation of colour, I have adopted it here.

Since three observers are inclined to one opinion, and one only holds the contrary, I should be inclined to suspect some anomalous vision to have vitiated Mr. Purklss's observation; and tho object of tho present communication is to ask your readers whether an abnormal vision, manifested in any considerable degree, as in some of the cases specified by " Omicron," would be likely to produce telescopes in which chromatic aberration would not be duly corrected. It appears to me that if tho correction can by computed by mathematical formukc, it is n-»t likely to produce any ill effect; but if tho correction be dctcnnluud by continued examination of the image of an object, and continual grinding, till the object H seen to the satisfaction of the observer, depending upou no fixed law, but left to the option of the observer, the question is one of some Importance.

It Is needless for me to say that I am Iguorant of the method employed by makers for correcting the chromatic aberration of telescopes ; and if it is not asking Mr. Purkiss to reveal the secrets of his guild, I should be glad if he would give me some information, especially as regards refractors. Columbus.

THE TELESCOPK. Sir,—ManythankBto"F.U.A.S,M for his kind answers to my last queries. The reason I asked would he think a 3in. telescope good, was because 1 saw among tho testimonials to Solomon's ,C5 telescope, the following from the Rev. P. K. Winslow, " In Mr. Proctor's book on the Telescope. I find the following passage about the trapezium. 'The trapezium affords a useful test for the light-gathering power of the telescope. Large instruments exhibit nine stars; but our observer may be well satisfied with his instrument and his eyesight If he can see live with 3J-inch aperture: a good 3in. glass shows four distinctly, but with smaller apertures ouly three are visible, and in a note he adds, * I have never been able to see more than four with :j£in. aperture.' Now with the telescope I obtained from you last year, I can see five stars in the trapezium." All Solomon's .-£,"» telescopes aie warranted to show five stars in the trapezium0Oriouis. It was in pages* of the currentvolume.that " F.R.A.S." eaid, in auswerto "A Poor Lad," " A 2Jin. object glass could not possibly divorce anything closer thau a pair of stars L,;"5 apart;" however, " F.R. A.is." may not h;ive mount a G mag. pair. And now, iSir, I must with your permission, trespass on " F.R.A.S.' «"' kindness a little more. Would he be so kind as to answer the following queries :—l«t. Where can I obtain tho "Nautical Almanac," and what is its price I 2nd. What moderately cheap book gives the best list of II.A. and declinations? :;rd. Is there any essential difference in the mounting of reflectors' -"id refractors .' That is would it not do to take a 'iel for a wmall refractor from an Equatoreal refleetoi. 4th. How can I calculate the field of view that any given Huygheniau eye

piece would have with any given O. G.? An examplewould greatly oblige. 5th. How are the webs in a transit eyepiece protected? 6th. What is the plan of the paneratic eyepiece? I have often heard ot It, but never saw one. 7th. Is Kepler's third law exact? *th. nouldnot" F.R.A.S." describe a spectroscope more minutely than he did in No. 2(»7? I am sure it would be Interesting to a great many of us, especially now as b© is going to tell us something of its uses. 0th. What i» tho size of the Cambridge (U.S.) refractor, and also the Melbourne Telescope? Scorpio.

P.S. How could I find the focal length of a small concave lens.

WATER ANALYSES.

Sin—With reference to the letter signed " W. R.* in your issue for May 13, page 187, there are or rather were four modes of estimating the organic matter in water Firstly, the original old method of treatintr the solid residue obtained by evaporating the water to dryness, and estimating the loss, which wa* ascribed to "organic matter." This is now quite abandoned as being unsatisfactory and altogether erroneous.

Secondly, there is the system of estimating the "organic matter" by moan* of an acid solution of permanganate of potash, as detailed by Prof. Miller in his paper entitled "Observations on Some PoinU in the Analyses of Potable Waters." iu the " Journal ol the Chemical Society," 180-5. Vol. XVIII. This, however, has been proved to oe quite unreliable, besides being unsatisfactory at the best. In fact. Prof. Frankland's comment on it, "totally untrustworthy," has been thoroughly well sustained by succeeding trials with it.

The third system is that of Messrs. Wanklyn, Chapman and Miles Smith, and is detniledat length in their paper on "Water Analyses," road before the Chemical Society on tho aorh of June, 1807. This system which was criticised by Mr. Dugald Campbell (" Laboratory," Vol. I.,) and again verified and slightly amended by Prof. Wanklyn in his " Verification of Messrs, Wauklyn,Chapman and Smith'sMethod of Water Analyn<*»" in the "Journal of the Chemical Society,"new series. Vol V., p. V.H, dtsputeswlth Professor Frankland'smathod the claim for pre-eminence.

The fourth system Is that of " Frankland and Armstrong," tho principle of which is detailed by Mr. Davis on pa^e s? of the English Mechanic. Thl* system is based on a gasoraetrlc estimation of tho organic nitrogen and carbon, and tfavrelicaHy is the finest and most accurate of the four. Professor Frankland's paper iu the "Journal of tho Chemical Society" violently attacks the method of Me«rs. Wanklyn, Chapman and Smith, and in It the author attempts to demonstrate the thorough unreliability of their system by means of a systematic series ol analyses, comparing the results obtained by IU use ol Messrs. Wanklyn'*. &c. method, with the results furnished by his and Anmtrowj's proms, and putting down the former as wrong on account cf tho difference between tho former and the lat'er, which is assumed to be correct.

Prof. Wanklyn retaliated, and iu the "Journal of the Chemical Society," Vol. XX.. attempts to prove the unreliable character in practice of Fraukland and Armstrong's method of gasometric analysis, and vigorously defends his own system, lie also shows by reference to Mr. Miles Smith's paper in the "Laboratory,"' Vol. I., p. 114, the danger and liability to error of tiny result based ou thenualysesof the residue obtained by evaporating to dryness a larjje quantity of water. Since then the dKcu-^iou and rivalry between the twomethods has waxed hot, Professors Wanklyn, Schouk, and Chapman having Improved their position by their masterly analysis of the "Action of Limited Oxydlsation on Nitro and Nitrogenous Organic Bodies," and of the action of Jiikuline permanganate of potass on organic bodies. Professor Frankland in turn has improved tho reliability ot his system by Mr. Herbert McLcod's papers " On a New Form of Apparatus for Gas Analysis," in the September number of the "Journal of the Chemical Society," 1869. and " Apparatus for Determining tho Quantities of Gases Existing in Solution in Natural Waters." in the "Journal of the Chemical Society," Vol. VII., new series; and Or. Russell's paper read before the British Association, lbOO.

It is at present difficult to determine which is absolutely the best. With our present knowledge, perhaps, theoretically Frankland's is the most accurate, but a systematic research may at any time turn the tables, and leave Wanklyn's the best, while chemists are undecided, many taking each side, while others, the majority, take neither.

Neither the alkaline permanganate process of Prof. Wanklyu and his colleague at the London Institution; nor the gasometric system of Prof. Frankland, and the Koyal College of Chemistry, however, are perfect, and, strange as It may seem, neither of them are capable of correctly and accurately estimating the actual amount of tho nitrogenous organic mutter, a<* Dr. Phipson and Mr. Paul remark. It is true Dr. Frankland, in his article in Vol. XX.,page 72,ot the "Journal of the Chemical Society,''goes so far as to deny itsproctibility at present, but, that U too sweeping a conclusion.

At present, therefore, Professor Frankland's system used io connection with the Royal College of Chemistry apparatus, as detailed in No. 81 of tho new series of tho '■ Journal of the Chemical Society," and by experienced hands, is theoretically the best, and iu practice may yield tho most accurate results. Hut, on the other hand, it is long, difficult, aud complicated, utterly unreliable In inexperienced hands, and, from its very complication, liable to (.'rave errors, which the number of reductions and calculations afford every chance of being increased to a serious extent in potsintr through these manipulations. These, in conuection with other mutters, operate to such a degree as to rehder it possible that no two analyses ot tho same water will agree.

Finally, therefore, in practice, Frankland and Armstrong's process is not to be depended on unless a long scries is taken, and tho average struck off; while its complication, difficulty, aud length, together with the complex apparatus and many reductions aud calculations, render it so liable to serious error* as to quite outweigh tho advantage it has of affording the total empirical formulae of the organic substance. It also has the disadvantage of giving no easy standard of comparison with others, and of not in the slightest classifying the organic matter.

3lessrs. Wanklyu. Chapman, and Smith's process is indisputably the shortest aud easieit, and moreover is such as can readily be done by anyone. Jt enjoys the advantage of classifying direct tlie nitrates, nitrites, ammonia, urea, and albuminoidous and nitrogenous organic matter into separate classes. It is very little liable to error, and besides affording an easy standard of comparison, can always be depended on to afford an exact agreement in its result between waters of the same composition.

It has been alleged against it that with waters containing the same exact amount of nitrogenous organic matters, but of different constituents, it will yield different analyses, and that with waters of different quantities of oxydiscd aud nitrogenous organic matter of"different constitution it will yield similar result*. This is true, to a slight extent it will, but the gasometric system does the same to a far creator extent. It has also been stated that Messrs. Wauklyn, Chapman, and Smith's, pennangauate of potass process suffers under the objection of being liable in a certain degree to under-estimatc the nitrogenous matter; this is also, to a certain extent, true, as it is indisputably passible forit to so happen, but it could only so occur with perfectly harmless compounds, not known to exist in water, and then to but a very small degree. Messrs. Frankland aud Armstrong's gaaometric system labours under the much more serious difficulty of being extremely liablelto very considerably over-estimate the nitrogen, and of confounding the innoxious and the dangerous nitrogenous matters together.

From the above, your correspondent "W. It" will gather that personally I am of opinion that at present, for general purposes, Messrs. Wauklyn, Chapman and Smith's permanganate process is the best, though for some purposes, Messrs. Frankland and Armstrong's gasometric system in preferable.

In reply to his queries, it is possible to use both Wauklyn and Frankland's process for sewage analyse-', and. perhaps, for that course of analysis, it would be as well to estimate the total nitrogenous matter by Frankland's system, and confine Wanklyn's to free ammonia, urea, and albumiuoids.

Nessler's test can satisfactorily be employed for estimating ammonia salts, and for small quantities is much better than standard acid.

Finally, it is practicable, but not advisable, to use Wanklyn's system for manures; neither thould I recommend Frankland's. Urban.

EXTRACTS FEOM CORRESPONDENCE.

TESTED RECIPES.—" A Morayshire Man " says: —" I am of opinion, with a number of otherjeorreapondents, that those furnishing answers to queries for recipes should add whether they have been tried and proved, or, if they were extracted from some author, as the case may be. I am confident a number of these answers are not worththe space they occupy, and, consequently, a loss of time and money to many a one who tries them, both of which the person may be ill able to spare. And with a few consecutive failures, many a person may become disgusted with the recipes (never blaming himself of course*, and if not the loss or" a subscriber to the Mechanic, at least the loss of a correspondent. I have found a number of these recipes useless. Not at all times so much the lan't of the recipe itself, as to the manner of preparing it."

THE EAR.—"H. doS." says;-"Dr. Usher writes of having often been an hour in removing a plug of wax, and adds a caution against (lie common and indiscriminate u*e of the syringe. Will he allow mo to inform him that glycerine dropped into the ear dissolves the cerumen, winch is occasionally secreted in morbidly excessive quantity in the outer meatus of the ear in eld people and in young children; and nl->o that iv certain form* of deafness, arisinjr from a deficiency tf the waxy secretion, it works often like a charm when dropped into the meatus, so as to lubricate that passage and the external surface of the rueinbranatympanir For this I am indebted to Dr. Abbotts Smith's two Utile books on glycerine.*'

MIND AND BODY.—Edmund Lawrance says :— "Being deeply interested in the subject of ' Mind.' I joyfully hail the appearance of Dr. Mnudslcy's lectures in the Enolisii Mechanic. Mancousistsof two parts only—soul and body Mind Is the action of the soul. The soul per ie is not only ignorant aud dark, but totally unconscious of its own existence; as, dining perfect sleep, a faint, or upon concussion of the brain. When, however, the nerve waves are set. in motion, the soul not only becomes conscious of existence and recipient of present Impressions, pleasurable or painful, but it. also finds it has the faculty of marshalling and reviewing the impressions received aud registered by the nervous system during a whole lifetime. But the soul is utterly dependent upon the integrity of the brain register. If the images be distorted or misplaced by disease, the soul still accepts tho*e in simple faith, and. attempting to reuson upou them, produces the well-known phenomena of insanity."

COTTON SPINNING.—" B. H., Rnehdale" writes: —" I have read with interest the several letters on • Cotton Spinning,' on page 1*2 and ltf:i, and in reply to • H. C, S.V insertion that there is not, or ontjht not to be, any draught between the lap roller and feed rollers, he cannot have examined the question in a

? roper manner, or he Would find that it is as needful n that part of the engine as any other, although it is 1 very small—say, 1 —In. With respect to the rule lie

10 gives for the draught of drawing rollers, he Is perfectly right, as far as computing them together <rocs, and E, Slater will find that by his rule (if he gives the roller* the proportion he has set out, and then takes

the whole draught of the rollers together) that he has a draught of 12 insttad of 7."

READINGS FROM THE GLOBES.—J. Dyer states:—"In 'T. S. II.'e * letter, entitled 'Readings from the Globes,' at r-age 208 of the English Mechanic, the following statement is made:—'As the globe turns on its axis from west to east, those who live in west longitude must have their time earlier lhau those living in east longitude, because they will not eorne into the enlightened hemisphere so soon.' The word rarli'-r should be later. As the sentence stands, the last part contradicts the first."

THE WANDSWORTH TELESCOPE—E. Salter says :—" Having recently come to reside in this locality (Clapham Junction), and noticing Mr. Webb's Late remarks respecting the great Wandsworth Telescope, I have been induced to try to seekitout. After two or three failures I met near the spot ou which It used to stand a gentleman named S til well, an inhabitant of Wandsworth, who gave roe the following particulars from his own personal knowledge. Pointing out the enclosure within which the Instrument Whs erected, aud indicating markings in the ground left by tho tower from which it swung, he said that the whole affair was removed four or five years ago. The bricks were employed to aid in the erection of nn hotel visible a few hundred yards off; the tube was bought by a Wandsworth broken, who cut it Into sections, and sold them to a gentleman at Wimbledon. These sections, with bottoms inverted, formed tanks, lrom which the gentleman's cattle now drink. About the tramway there was some four tous of wrought iron, which Mr. S til well himself had converted into horse-shots. As to tho object glass, my informant could tell mo nothing."

REPLIES TO QUERIES.

[200?.]— TEMPERING DRILLS—If the drill Is a

small one hold it in a jet of gas till a cherry red heat

appears, then dip the point, or as far up as you wish

It tempered, into water or oil immediately. Then try

if a smooth file will bite or file it[; If it does, it must be

done over again, but if it does not bite, but flips over

the face without making any impression on it, it will

do. Next clean the point or side ot the face carefully

on an oil stone, then twist a piece of wire round the

end of the drill, or hold the end of the drill In pliers,

or a candle or gas light till you see it (on tho clean

piece of the face) gradually turn from a light to a dark

'straw colour; withdraw from the heat, and allow it to

I cool gradually. If it goes past the dark straw colour

! to a blue it will be rather soft, and must be dipped In

j water or oil at oueo, or els'1 the process gone over agaiu.

; The above dark straw colour will bore brass beautifully.

If it is to bore steel or iron, I have mine just as hard

as when they come out of the water or oil in the first

process, but care netds to be taken with them if very

small in that condition, as tney are very brittle. I have

made several dozens in the above way during the lost

14 years I have been working at my present profession.

—A Morayshire Man.

[3186.]—BAR03IE TEi: TUBES.-" Compensation" can clean his barometer tubes by washing with soap and warm water, and drying in an oven, or on a stove; or wash with spirits of wine, nnd it will dry itself when the spirit evaporates, or if the tube is very dirty, I have used fine sand with soap and warm water. But I do not approve of the sand, because it is apt to scratch the inside of the tube, which causes more friction on the mercury risiug in the tube, and consequently the barometer cannot bo so correct.—A MoRayshire Man.

[2363]—SILVERING CLOCK DIALS.—If "Poor Clock Jobber," 23ri/{, page tkS, cariies the recipe"givou him by "J. M.. IJirinUiLrham," into execution, without further or fuller instructions, he will liiiel his clock dial in about two or three months covered over with green spots, not because the recipe is a bad one. It is good if fuller explained. If " Cluck Jobber '* will put a piece of silver in a tea cup, cover it over with nitric acid (aquafortis), he will find the acid begin to boil. If it does not, hold the cup over a jet of gas. or put it on a slow tire till it begins to boil. Take It off the lire, and it will boil away till the silver is dissolved, if ho requites mote acid (owing to the acid not being pure) he can add a little, but the first quantity should do for dissolving a 5d. When dissolved, he will have a green deposit. Fill the cup with warm water, stir well to wash the silver, throw in grnduallv as much table salt as a penny piece will lift, desist stirring after the salt is put in, and allow the solution m settle a few miuutes. The salt will precipitate the silver to the bottom of the cup. Pour*it the water in the cup, care being taken not to pour oft any of the solution, and when pourod off as eiean as can be without taking any of the solution wiili it, evaporate the remainder of the moisture above a jet of gas, or otherwise, till the solution is in a thickish kind of paste ; when this Is done, fill up Lhe cup agaiu with warm water, aud repeat the process till the solution comes to a milky whiteness, and you are sure all the nitric acid is out of the solution. Iwo or three washings is amply sufficient; if any trace of tho acid remain It will in time (notwithstanding the varnish) eat into the dial or other article, causing a number of greens pots to appear ,as it were, on the surface of the silver. "Poor Clock Jobber " will at once see the advisability ot well washing his solution. The parts to be silvered must bo well cleaned with flue Hour, emery sheet, or paper. No grease or dirt must touch the article, especially when finishing, uot even the hands must touch it if possible. When well cleaned, and all traces of previous silvering, or lacquering off the article (I would not advise "Poor Clock Jobber" to wash the article at this stngeof the proceedings), take a piece ot wash bather or soft cotton rag. soak it in water, dip it in a little salt. Rub the dial over with this first, pretty smartly. This makes the solution take ou better. Then dip ihe rag in cream of taitar, and also in the solution (for they maybe mixed

together), and rub woll on, aud if this does not silver "Poor Clock Jobber's" dial, I shall be apt to say with tho Editor (see p. (36). After it is well silvered, wash in clean water (only). Dry with a soft towel ; when dry hold the back of dial close to a fire or qn a stove till it heats a little, not to be so hot as to melt the wax in the chapters. Then varnish with a soft brush, varnish to be made by dissolving gum mastic In spirits of wine; the %-arijish requires to oe rather thin, and tho article will be ready in five minutes to be Bent homo. I have done the above frequently with brass dials, and found no trouble with them afterwards. "Poor Clock Jobber " may think I have been too long In answering the above. But to explain. I get the Mechanic ouly in monthly parts at the beginning of each month, and when it leaves the bookseller's shop from whom I get it, it comes Is miles by rail en; I get possession of it, the carriage by rail of which I pay over and above the regular price of publication.—A Morayshire Mas.

[24150—GALVANIC BANDS.—The width of metal strips for galvanic bands is of no consequeuce : the broader the more action. I have generally made them about fin. wide. To " whip " the joints with thread is merely to wind thread round them in a close coil. List is the woolly selvage from cloth, for which ask your tailor; it matters not which side is worn next the skin, provided the bare metal at the end of tho band touches it.—Suffolk Amateur.

[2,518.]—GAUGE FOR KITCHEN BOILER—My opinion Is that if the boiler 1b properly fixed at tho back of the kitchen range, the flow and return pipes properly erected from the boiler to the hot water cistern, a water gauge would bo useless. For this reason, when hot water is drawn for use, it is not drawn from tho boiler but from the hot water cistern, through pipes connected to the return pipe. Consequently when there Is no hot water, it is a proof that the cistern is empty, and uot the boiler, and a fitter is called in before auy damage is done to the boiler.— J. O.

[2.VAS.]—MUSICAL. BOX.—From the poor way in which I expressed myself on p. 164,1 may not quite be understood. The loth and 17th lines should read. "The right end of the roller comes slightly over the cU<je of the same (Hint's the roller), and is caught in a slit," Ac—Harry Bertram.

[25670—CHIMING CLOCK.-If " Toodlea " will get three or four spiral springs something like what are found in the inside of couches, easy chairs, ic, lay them in the bottom of his clock case, lay a flat board on tho top of them, or a bag of wood shavings, hay or straw, he will find that when the weight falls, coming In contact with the spring's they will cause tho weight to rebound, and so break the falL—A Morayshire Man.

[2577.]—BORING GLASS.—This question relative to cutting circular holes in glass, does not appear to have becu satisfactorily answered. As I, some time ago, required certain glass^diso* with holes in them, I went to Palmer's, in St. Mart fn's-lanc. and 1 will, with your permission describe how their cutter proceeded. There was, on alow table, a circular disc of about a foot in diameter, covered with cloth, and mounted ou a pivot, so as to revolve on its centre, and there wa-* a mark to indicate this centre on the top of the disc. Then there was a firm upright fixed in the table near the circumference of the disc. Through a hole near the top of the upright slid a graduated arm, and to the end oi the arm was affixed a glazier's diamond pencil which could be slid down so as to bear upou the disc. Now supposing I wanted a circular plate fiin. In diameter, with a hole iu the middle of 2in. diameter, A square of glass of rather more than Gin. in the side was placed on the disc, the arm was adjusted so a* to bring tho diamond to bear at 3in. from the centre, the disc was turned by the hand, and a circle of Gin. thus described on the glass; the arm was now set at lin. from tho centre and the Inner circle scratched. The glass was then removed and placed on tho usual fiat cutting board, a rule was applied and a few cuts made with another diamond from the outer circumlerence to the sides of the square. This enabled the workmau to remove tin,* superfluous glass from the outside of the circle. He then applied the rule agaiu, and made S or 10 cuts across the iuuer circle, and crossed these a»ain with about as many more. Then taking tho glass in bis left hand, aud a pair of iron pliers in his right, he began tapping lightly on tho part that was cross cut, when nearly the whole fell out iu fragments, and any obstinate pieces were taken olf with a grasp of the pliers. The whole p rocess was gone through with great rudidtty, and was very dexterously done.—

F. n. c. s.

[2582.|-WEIGHT OF FRUSTUM.—TO Mr. TOLHAUSEN.—

II V = — X jr (R3 + r2 +■ Rr) = 4 X 3,1410 (4 + 1 +

1)

[ocr errors]

12*5664 x 7
440 11

which, multiplied by or — gives very nearly 17

8240 50 tons 27. By a simple error of copy our friend Mr. T. put 10 for 7— Bernardin.

[2600.]—CLEANING OF DIATOMS.--Thanks to Mr. Anderson (or his kind reply on the above, which I hope will give the desired result. In answer to Mr. A.'s query as to where I gather Diatoms, I may say that iu spring they are to be found iu almost any Kind of water. There is a small brook near my home, which I have bunted for a mile or two, and hire and there where branches of trees aud other obstructions lie across the stream, so as to be only partly submerged, I have several times discovered the deep ttrovn yeasty sewn, which betokens the presence of Diatoms. The most successful gatherings I have yet made, were in ditchescnt amongst osier beds. They may be fouud also in ponds aud ditches; if reeds, rushes, &c, be growiug in them, so much the more likely are they to contain Diatoms. 1 have fouud the following:—Amongst the Napkulce, A*. Ilhomho\dest A. A.itphhbana, N. Westii N. Didyrni. Pleurosigvue P. Attenuutitrn, P. JfitTiiltituiu, P. Spntcerii, Caceunenta Lanceolatvm, I'inunlaria viridis, Gomphontma Capitatum, EncyoncMa axpitosum, and several others, many of which I hare not yet identified to my satisfaction, as I am only a beginner in this interesting study.—Beaten.

[2634.]— PAPER HANGINGS.- As a continuation to A. Boughey's Information (which applies only to what is termed block printing) the question asked referring to machine printing, in machine work there are three principal divisions, viz., pulps (plain), grounds (coloured), and satins (both coloured and glazed). The first is printed plain—that is, without any preparation; the second is coloured with either white or any tint that may be required, and then printed; the third is coloured and polished before it is printed. To make grounds there Is a grounding machine (of these there are several sorts); the colour Is put on by it and smoothed with brushes, after which It runB through a long hot stove to dry, and at the end is formed either into folds or rolls, according to circumstances; it is then ready for printing. Satins are made somewhat similar to grounds, only that they have to go through what is called the polishing machine to be glazed. The printing machine is cylindrical, with revolving rollers pressed against It, on whose surface is placed or cut the pattern or form wbich each roller is intended to produce. When dried the printed paper is taken to the rolling machines and cut by young girls into pieces—Practical P.S.

[5M10-GALVANISINGCASTIRON.-The method is essentially tbo same as for sheet iron, but there is more difficulty In getting the zinc to adhere.—J. Meredith.

[2067.]—PAINT TO COVER TARRED WOOD.— All paint is affected when on a tarred surface, and the colour is generally turned to a green tint, a coating of lime, white wash, or two, would answer the end desired.—J. Meredith.

[2676.]— MODEL STEAM ENGINE.—"C R." was right when he said the model engine he Baw had a cylinder, pteton, fly-wheel, &c. Steam ouly acta on the piston during half a revolution of the fly-wheel, as will be seen by the following. A small block of metal is

[graphic]

fixed to the side of the cylinder at A, the face of which works steam-tight against the block II. The piston rod is fixed directly to the crank pin, so that when the engine is in motion the cylinder oscillates upou the pivot C. There are two holes in B, one the exVaust and the other the steamway. The hole in A serves for exh&uBt and steamway both. The action will be understood by examining the drawing. — W. H. Thorpe, Reading.

[.M79.]—HOW TO CURL AXD CURE HORSE HAIR.—In the first place I teased the hair well, then twined it into along rope with a hand twiner with the assistance of another person, having rolled it up into a ball, steeped it in water 24 hours, after that put it into an oven, taking care that the oven be not too hot to singe It; alter getting perfectly dried, I began to teaze U again, it is now ready for use. such as stuffiiug chairs, sofas, &c—A Helper Out Of A Fix.

[2683.]—IRON PALISADINGS.—The durability of ordinary paint or varnish would much depend upon whether the surface was free from rust or not. I would advise the use of Webster's patent zinc paint, which may be had from the patentee at Ozels-street, Birmingham.—J. Meredith.

[2693.]—KEEPING COPPER PLATES FLAT.Try reversing the plates.—T. S. U.

[2095.]—GEOGRAPHICAL QUERY.—" Key," as a correspondent, has said,is metimes the meaning of "quay," but also in several German languages " keizel, kef," has the meaning of flint or stouc. Let me propose then the translation "netber set key"—a stone where burdens were Bet down, or, a stone for sitting on; key-house, a stone-built house; "kcy-spink '*—stone finch, stone sparrow, the doubtful sparrow, FringiUa petroiiia, Linn. Those acquniuted with the locality will decide if lam right.—Bebnardih.

[3598] — " EMIGRANTS'" INQUIRIES. — Upon reference to a map it will be seen that Australia if nearly at the same distance to the south of the Equator as England is to the north; in fact It lies very near our antipodes—that is, if by any means a Hue could be drawn directly through the centre of the earth from this country, Australia would lie near the point Jit which the Hue appeared upon the other side of the world. It may, under these circumstances, be at onf«inferred that Australia possesses a somewhat similar climate to our own. Climate is influenced by many local features, and to these we iniiBt assign the differences of temperature which exist between tintwo countries. Australia, however, is superior :o

England In many respects: its winters are not so cold; its atmosphere is neither so foggy nor so damp; but is uniformly genial, mild,and dry. The summers, although occasionally much higher In temperature from the prevalence of north-weft winds blowing from the heated coast of Asia are scarcely so enervating or trying to the constitution from the bracing nature of the sea breezes. Beyond this the purity and freedom of the air from miasmatic influences and the usually noxious effects of night dews are such that a person may sleep under ll the open canopy of heaven" at night during the greater part of the year without endangering his health or constitution. Regarding the colony of South Australia more particularly, I may say that generally the above description of climate is applicable to this part of the continent, although of course the proximity of mountains, rivers, arms of the sea, &c, will cause slight differences, according to locality. The resources of this colony are chiefly mineral, yet agriculture and sheep-farming are pursued to an enermous extent. The colony, however, may still be said to be in an embryo ftate, and Is capable of sustaining a population of probably not less than 50,000,000 of people, whilst at the present moment there are not more thau between 1 or 200,000 scattered over Its enormous extent The land 1b fertile, the yield of grain being large; of carefully cultivated, giving frequently OtTor "Obshl. to the acre. Its capabilities have been briefly summed up by one of the governors as \ adapted to agriculture, h to pasturoage, and 4 barren and unfit for either. The above will give J. Francis some slight information about the colony. If it is too superficial, I am ready to enter into detail, but wish aa far as possible to condense this kind of writing, so long as the required information is imparted, so as not to occupy too much space. No one should emigrate to South Australia who is afraid of work. Do not go there with a firm intention to stick to your trade, for the probability is that you will find yourself before long lollowlng thecalllng of a shepherd. There is no shame in this, doctors and lawyers, Ac, have tried their hands, and have succeeded admirably. The man who can handle tools, mend carts, repair farming imp lements, Ac, is fortunate, be can command higher wages than his more unskilled fellow, even if employed upoa a sheep-run, for being at a long distance from a large town, resources at hand arc of great value. The best time of the year for sailing from England is during the autumn, as you will then arrive in Australia duriugthe summer. I cannot state the best placo for your ultimate destination ; the demand for labour varying, as in all other places. Speaking of the neighbouring colouy of Victoria, Mr Westgarth says:—" Hence a long array of miscellaneous arrivals, new and old, contiuuously out of work, while the skilled workman—the blacksmith, the carpenter, the stonemason- is but little beholden to employers, tights with them successfully at times over an eight hours' instead of ten hours' labour question at the same wages; and withal, in a country uowon the whole cheaper to live in than England, carus as much in one day as manv a home family must be content with for a week." This is a Ilttl; exaggerated, for which allowauce must be made, (Books consulted for information—"Guide to Australia, by a Merchant;" "Westgarth's Colony of Victoria;" "Maury's Physical Geography of the Sea;" "The Harrow School Atlas "—EssaysJ-F.R.G.S.

[3703.]—PASTEHOARD.—Screw them up in a napkin press before they are quite dry for 12 hours ; air them and repeat the process. 2nd, paste the edges of the first sheet of paper on a board or door; add as many sheets as yon require for thickness, and cut off when quite dry. 1 have made equally good boards by both methods.—T. S. U.

[3706.]—PANCRATIC TUBE.—This may be Illustrated on a small scale with any telescope. Unscrew the eyehole, draw out the small tube containing the two eyglasses us far out us it can conveniently be held by the lingers to be steady, and push in the focusing tube for distinct vision. An immediate increase of magnifying power will at once be evident In all glasses with this appendage, the eye-tube mentioned above is contained within another, to wbich the thread of tlie eyehole screw is fixed, instead of to the outside polished brass tube. Iu Solomon's 3in. telescope, this tube reaches nearly to the field glass (the 4th from the eye), so that when fully drawn out, the length of the day eyepiece Ik doubled, and the sun and moon can he distinctly examined throughout the length of the tube, the magnifying power increasing according to iu lenptb. Itis so long since I had them made, I forget tlie price, but should say from 4s. to 0s. Can be made bv any optician. With a clear-sky and good light this tube is equally applicable to terrestrial objects. Kor this telescope, I find the "Dean disc ulass" for day powers, supplemented by one of deep blue for solar observation, answers perfectly, absorbing all the glare, and reducing the suu to the brightness of

2 a white cloud. For a 2 — In. telescope, I find a glass

8 of "London smoke," one of deep and one of a lighter blue required. "Dean's disc" of " London smoke" may now he hud from Messrs. Solomon** lor 4s. 0d., the other glasses will be cut by any plumber for a Id. each.—Amateur.

[3709,1—TURNING.—There Is an error; the word "never" should not be there. It reverses the very meaning of the answer. It should read "An amateur will find a coarse, sharp, new flle," &,c.~ Q.

YOKKE.

[3700]—TURNING. — Sec answer amongst the Letters.

[3710.]-ARITHMETICAL QUERY.—If C c, represent the circumferences of any two different circles, aud D & their diameters, then

C : c ;: D : d

This fixed namber is generally represented by too
Greek letter ^ (read pi), the first letter of the word
periphery or circumfereHce. So that if
C

— = 7T

D

C = 7T X D

Now this number is the same for every circle, and it is obviouB that a single accurate measurement should be sufficient to determine it. It might appear at first sight that nothing can be more easy than to lake a perfectly constructed circle and measure Its circumference with a cord: and then measure the diameter m like manner, and find the ratio of two measuremeuts, which will give the numerical value of jr But It is found that the ratio of, the circumference of a circle to Its diameter cannot be exactly expressed in numbers. Each separately cau \<v measured with perfect exactness, but both do not admit of being measured exactly b y the same linear unit, however

22 1

small that unit may be. Practically — or 3 — is

7 7

found to express for many purposes with sufficient

355 exactness the value of j: — is still nearer, but

113 3 1410 or 314159 Is In general use. Now, suppose we have a regular polygon with a perimeter of 8 and number of sides 4. i'hen 1* is the rad. of inscribed circle, and 1-414213 is found to be the radius of circumscribed circle. Also if we have a regular polygon of 4<WJ sides with the same perimeter, the rad. of inscribed circlets 1*278239, and that of the circumscribed circle Is the same. Thus the circumference of either circle will not differ from the perimeter of the polygon between them by a quantity sogreat as '00001 because the radii do not. So that wo may conclude that the circle whose circumference is 8 has a radius equal to> 1*373239 But

circum. circum.
Jt = or

2 x rad. diam.
S

[ocr errors][ocr errors]
[table]

C : I>:: c : d
C C

D d

or the circumference of :i circle bears an invariable ratio to its diameter, aud of course to Its radius.

The area of a circle ll found by the formula (diameter) *x *7854. Now the circumscribed square is equal to the square of one of its sides, which is equal to the diameter of the circle. Therefore we must multiply areas of squares by the decimal -7S54 to net areas of circles; and not areas of circles to get area oi squares.—J. G. G.

[8717.:—COFPKR AXD SILVER COINS.—The first is a Kreucli coin of Duke of Rohan ; the second an Arabian.—Collector.

[8718.1 -TALL CHIMNEYS.— The great chimney at St. Koltox, Glasgow :—

Total height from foundations...
Depth from foundations

Total height above the surface

Diameter at base

,, surface

,, top

There are used in its construction l,2i0,000 bricks of first quality, weighing 1211b. per cub. ft, the brickwork is 31 bricks at the bottom, aud 1J at top. Tlie peculiar construction Is that of a double cone, the Intern >il flue is200ft. high, and la perfectly vertical.— E. N.

L:1721.]—GRINDING.—In answering the inquiry of "Scrgius," I should Bay that 4 bush, per hour, more or less, was a fair avernge for a 4ft. stone running 120 revolutions per minute; but 200 revolutions for a pair of 3ft. 4in. seems to me too fast. Terapleton gives 150as speed for Win. 6touc.dividiug6 00 by the diameter iu inches; hut it is a bone of contention with millers as to how much a stone ought to do, even wilh plenty of power; some not liking to do more than 3 bush., others will advocate 5, much depending on the stone at d the dryness of wheat: and I should not be surprised if my letter gives rise to more controversy than the balancing business, of which so mnch difference of opinion exists—solely, I believe, because a stone that is in standing balance is generally in running balance, or so near to it as not to be felt when there is a moderale amount of feed uuder: aud I believe there are millers who would boast a life of experience without knowing their stones were out of a running balance, Bimply because they never ruu them empty to try. I have i pairs of 3ft. loin, which will do 4 bush, per hour well. I have also a pair of 4ft. Oin. which will do 10 bush, per hour well, aud work well, hut they have 5im. draft. These said 4lt. (iin. had formerly 2in. draft, aud 1 understand they would ouly do 4 bush, per hour; the alteration was made by running all the furrows into the master furrow; thus making a second furrow of the master furrow. There is a pair of 4ft. 4in. laying beside them, both driven by wind, running the same speed; but they will not do so much by about 3 bush, per hour, although thev had the same alteration made iu the draft and furrows at about the same time—say 40 years ago. Now I have seen these two pairs of stones do nearly a load of wheat iu 2 hours. We find no disadvantage from the extreme draft, but dare not carry much furrow.—One Kye.

ni723.]-GrfAZE Fun I'OTTKRY.-IOO parts white lead, 20 do. Hint, 40 do. Hint, 5 do. whiting. This glaze Is colourless; to make it a brown ghizondd IS parts of oxide of manganese aud 18 parts more white lend; to make a blue glaze, substitute for manganese 9 parts of oxide of cobalt. Shall be happy to afford "X. N." any information he may require upon this subject.—K.

[3798J—GLAZE KOR POT IKIIY.-Ccmsult specification of Patent 3'57, 30lU October, 1*07, at your nearest public free library, wbich I think may give the information you require.—A. Tolhauben.

[3723.]—VULCANISING RUBBER.—The rubber ready mixed with sulphur for vulcanising, may bo obtained from C. Macintosh and Co., Cambridge-street, Manchester, and London, or David Moseley, Manchester The price will depend on the proportion of sulphur, required, which varies for each special purpose, perhaps 2s. 6d. or 3s. per lb., in quantities. The moulds Bbonld be pure tin or plaster of Paris. Iron combines with the sulphur, and destroys the nature of the rubber. Any steiun tight chamber may be used for vulcanising in (which will stand the pressure) Information respecting the time required, and the pressure, may be obtained from the persons who supply the rubber, or you might try a pressure of 50 or 551b. on tho In. for 3 or 4 hours. When you get It exactly as you want it, adhere strictly to the same timo and pressure, as the slightest variation alters the nature of the rubber.— A Dentist.

[3725.]—OILED PArER.—Hauscl, of Neustadt, recommends petroleum applied to writing or drawing paper, and properly dried by blotting paper.—A.

TO I. HA US Eli.

[3730.]-PAPER COLLARS AND CUFFS.-A neat machine for the manufacture of collars, caffs, and other articles of dress mode of paper and cloth combined, was patented by Mr. Benjamin Browne, in 188S. The material Is first operated upon to represent stitching, creased for folding, the button holes punched, and the ends cut off to the desired shape; the article is then discharged from the machine, and another feed of paper supplied and operated upon as before, and so on in succession. Finally the article is passed by an endless belt between rollers for finishing it (vide specification, A.d.,186s, lflth March, No. 1040).—A.

ToLnAKSEN.

[3733.]—COTTON SPINNING.—J. A. Hulsse,"Die Tichnik der Baumwollspinnerei," Stuttgart and Augsburg 1857 - J D. Fischer. " Dirpraktische Baumwoll•pinner," Leipzig, )e55; C. H. Schmidt. "Lehrbuch der Spinnereimechanik," Leipzig, 1857: K. Karmarsch, "Ilandbuch der mech. Teehnologie," Hannover, 1858; Bd.S.10o6—1103—Supplement zu Prechtl's Tlchnologlscher Encyclopadie, (Karmarsch), Stuttgart, 1857. The above books may be had in London. Trubner and Co., Paternoster-row. BennoNicss, " Die Baumwollen Spinnerei in all ihren Theilen" Volgt in Weimar; Dr. E. Hnrtzig in Dresden Versuche uber den Kraftbedarf der Maschinen in der Flachs nnd Wergspinnerel; Schweiz. l'olyt. Zutschrift Vol. XlV°Heft 5. Sutel28.—A. ToLnAUBEN. I. [S7;|9.]—CHLORIDE OF TIN.—Three chlorides of tin arc known, corresponding to the oxide*, namely SnClJ, 8nCl«. and SnCU. See Wntts's "Diet, of Chem." vol 5. page 800.—A. SoLnAiSEN.

[3739.''—CHLORIDE OF TIN.—If this querist will ask at a manufacturing chemist's for protocttUir'nlc of tin, he will most likely get what he requires—A. T.

[37410—TURBINE—In answer to " M.R.C.S.," if he will write to me I will try to assist him to sue a turbine, as there are three in my neighbourhood — John Wild. Shuttlcwortli, near Bury, Lancashire.

[3750.]—SILVER COIN—la a penny of Baldred. Kins of Kent (the lust). Obv.: Kings bust to right; Baldred Rex. Rev: Moucyer's name —Edelmod Moneta, small cross, 7 rays issuing (scarce). Should be glad to communicnto with "Beginner."—J. H. D., Stretton-on-Dunsmore, Rugby.

[3751.3 —ASCARIDES. — A great sufferer from nscaridea should take 20 drops of tincture of iron in infusion of quassia twice or three times a day for a month, and use an Injection of common salt dissolved in wnter, but not made too strong, occasionally. This generally succeeds, but cases differ, nnd no case can be satisfactorily trented by correspondence. Any chemist can make up the above prescription.—M.D.

[3753.]—BOTANY.—A"Manualof Botany,"by Robert Bentley, Professor to the Pharmaceutical Society, published by Mr. Churchill, 12s. M., is the standard work vpon which the students are examined, and Is decidedly the best.—F. H . H.

[3753.] — BOTANY. — Use Babington's " Manual of British Botany," or a similar work by Johns. The latter is more popular, and easier to work with, and costs about 7s. 1 believe.—M. D.

[3762.]—PAINTING AND DECORATION.—The best work on house decoration and painting that I have seen, is by William Sutherland, Manchester; obtainable from Simpkin, Marshall, and Co., , Stationers' Hall-court; Abel Hey wood and Son, 5C and 53, Oldham-street, Manchester.—Painter.

[37<S3.]—THEINE.—I perfectly succeeded in the Isolation »f thelne by operating on 21b. of the best green tea as follows:—2gal. of distilled water, where brought t) the boiling point in a Btill of 4gal. capacity; I now shoot in the tea, stir up for an instant, quickly lute the head on, connect it to a worm condenser, and ebullition commences. By the above arrangement of apparatus you will observe I was able to collect, previous to the isolation of the theine, another highly important compound of tea—viz., the essential oil. Note also, by having the water at a boil I avoided the risk of charring the leaves, wbich doubtless would have occurred it the still had been placed over the fire with cold water along with the tea. I kept it gently boiling for two hours. About lipt. of water passed over loaded with the oil. On agitating this water with ether, decanting and evaporating the ether, 1 obtained the oil in a separate form. This oil appeared to me to be a powerful Intoxicant, for on my warming it and 'applying my nose, it had an effect similar to smelling hydrocyanic acid of high per r.entage. I now set to work for tho thelne emptying the contents of the still on to a brown calico strainer euspended from spikes on a frame furnished with four legs, allowing the filtrate to run into a large tin vessel. I now pour 2gal. more of distilled water into the still, which 1 place over the fire; I collect the leaves off the strainer into n dish, and submit tbem by portions to powerful pressure in a tincture press, allowing the expressed liquid to flow on to the strainer. The hard cakes of leaves from the press 1 knock and break 1m to

ftleces, crumbling them into a loose heap. The water n the still is now boiling, the leaves are shot in again

and stirred; not tho head this tim?. bnt a lid Is put on. It Is now left for two hours In brisk ebullition, then strained and express."! as before A boiling solution of subacotatc of lend (acetate of lead 5 party, litharge 3J parts, distilled water 16 to 20 parts, boiled for half an hour) is poured in just as it Is (without filtering) till it ceases to occasion any precipitate. I allowed It to stand all night to settle Early on the following morning I drew off with a syphon as much of the clear supernatant fluid as 1 could; the precipitate I submit to pressure. I avoided the disagreeable process of sulphuretted hydrogen by the substitution of oxalic acid. The excess of lead was then thrown down as an Insoluble oxalide. I added a little ammonia to take up the free acid, drew off the clear liquid, boiled it down to 2pts. or so, poured it into a iettt. bottle, then allowed it to get cold (what beautiful crystals fill the liquid as It cools I); when cold 1 adied .ibout 4 fluid oz of chloroform to the contents of the bottle, and after briskly agitating them for 5 or 0 minutes I let them settle; the chloroform quickly fell to the bottom colourless and clear, whilst every crystal had vanished out of the liquid. The chloroformic solution of theine was then taken up by a glass tube, drawn out to a capillary point, and discharged into a flask. The chloroform was then distilled off by n water bath Into a Lleblg's condenser, and on detaching the finsk from the condenser I found the theine left dry and white. It gave me entire satisfaction In the shape of a good sample of thelne. I should be pleased to be equally successful with digitaline. Surely one of my brother readers has attempted digitaline with as happy a result as mine as regards to theine. If there is such a one among our many, may I beg of him to explain the way he proceeded?—Pharmaceutical Student.

[3703.]—CAFFEINE OR THEINE.—The general method adopted in the preparation from tea or coffee is by pouring on these boiling water, and mixing the Infusion with subucctate of lead to precipitate the tannin. Piligot adds subaeetate of lead in excess, then am monia. The mixture is boiled for some time, the lead-precipltfite carefully washed on a filter with boiling water, the filtrate freed from excess of lead by sulphuretted hydrogen, and after a second filtration, evaporated at a gentle heat. Oncooliug, It yields an abundant crystallisation of nearly pure thelne, and an additional quantity may be obtained by concentrating the mother liquid, and leaving it to crystallise. Caffeinebelng volatile, it mnynlso be prepared by sublimation, gradually heating waste useless tea In a sublimation apparatus. Part of the sublimate Is quito pure; the rest may be purified hy recrystalllsatiou from water. For further details riJe " Watts's Diet of Chemistry," from which the above has been extracted. —A. Tolhacsf.n.

r.3768].—POISONING BY CANTHARIDES—The effects of cantharldes arc only trausient, and the results attributed to it by the querist can only exist in his imagination.—M.D.

[3778.]—LIGHTHOUSES—The querist will find In "Mervellle's de la Science, pur L. Flguier " all the particulars he may d sire ; every nuinberof that work can be had separately ; lighthouses occupy, 1 believe, a or 0 numbers—BF.nxAnDiN.

[3732.]—BOILER —I do not know much about small boilers, further than their requiring much bigger fireboxes. In proportion, than large ones, on account of the difficulty of keeping a small tire alight. For such a boiler as " Hydraullcan" figures, possibly a well arranged gas Hre'woutd do. 1 should, for a coal fire, put about 14in. square of lire bars, then slope the wnlls of fire-box outwards at about 30° away from the perpendicular for, say, Sin., and then coutrnct tho walls again at about 45°, till your pot will just fit on. It is of an awkward shape to make n flue, round to water level, and I should say Beven 2' tubes would bo better than one. The brick work might be gradually altered from square at bottom to round at top; and the reason for the form I suggest, is to get a great surface for radiating heat, besides what is conveyed up the tubes. I should put the dead plate on n higher level than tho fire bars, even If It has to be made moveable for raking out the fire. Somebody who knows better than I. will, perhaps, give you n hint. I was very successful with a cylinder boiler only 4ft. long, by 2ft. diameter, which drove an engine 4J diameter and 8" stroke, for months, nnd the man In charge said he always had steam, and the fire-door generally open : of course only doing light work.—J. K. P.

[3794.]-POLISHING STEEL -TO"CYLINDER." —Use your " red stuff " on a bell metal polisher, which can be had at any watchmaker's tool shop, and you will get the black polish you so much ndniire. The scratches are caused by dust getting into the polishing stuff. The plvol "Cylinder" has marked A is a straight pivot, with the shoulder turned away after it is made. B is a cone pivot, which is proper lor a balance staff. The other is only an attempt. A cone pivot Is made bv first turning down nearly to size, and then polished with a polisher, tho Bhape made of a stick of straight steel wire. That part held In the hand should be draw-filed, to prevent slipping in tho fingers, and the other end filed the shape of a crossing file, to suit any shape, and give it a slight rotary motion backwards and forwards, as well as the longitudinal motion. This will prevent rings forming. When finished, turn a groove close to the pivot, to prevent the oil running up the staff, away from the pivot.—Viator.—P.S.—There are several other watchmaking questions asked this week; but the subject only interests the Individuals. I never yet heard of an amateur watchmaker.

[3804.]—WATCH CLEANING.—J D. Morgan will require for watch cleaning, a pair of tweezers, plyers. cutters, a screw-driver, and a brush. I myself (an amateur) got my tools and part information from the Watch Tool Warehouse, (S. Fauenbcrg's, of Leeds) j but perfection will come by practice.—N. T.

[3817]-STEAMING WOOD—The apparatus for steaming wood consists of n wooden chest, large enough t j contain the work. This Is connected with a covered boiler or copper, in which the steam Is generated. "W. B." does not state for what purpose he requires the stuff steamed, or the size of the s:mie. so that hisquery camiot be answered vitisfacuu ily. Large stuff requires

more steam than thin stuff. An inch oak board will Hike about twenty minutes, and sets in two or three hours. In forming moulds for tho hot timber to be shaped to, care should be taken to give a sharper curve than wanted, to allow for n alight reaction.—Boat Builder.

[3821.]—WHEEL CUTTING.—In reply to J. K., England, the teeth I cut were not wheel teeth, but floats similar to cabinet-floats, about loin, and 12in. long, for roughing the metnl off the tubes that gun barrelB are made of. The side view of them shows them to be like plt-saw-te 'th, and skewed on the face of the instrument like the iron of a skew rebate plane. I merely wished to point out that the difficulty of having change wheel of steel did not lie so much in the expense of merely cutting the teeth, as in obtaining the stuff to make large wheels of.—J. K. P.

[3822.]—FORCE PUMP.—U seems to me that "Guernsey Amateur" Is sufficiently exigennt iu wanting n drawing first made exactly to his requirements, and then to expect tho Editor of the English Mechanic to go to the expense of having it cut and printed; particularly as he does not seem apt at making on ordinary working drawing out. And yot he can give a description of the action of a chuck that hejhas[ncver seen. I hope he will not think I am pouring the vial of my wrath on him for the abuse I have received from an amateur In another of the Channel Islands. I think the best way of supplying a small boiler is to have a hand pump that will throw at least half a cubic Inch of water at a stroke; and to supply the boiler that way. where you see by the water gauge that It wants it. Small pumps are extremely troublesome; at least, I have found them 'so, as you have to stop the engine directly the pump ceases to act—viz., about once every half minute or so. You can pat a dummy, for the sake of appearance, to your model. — J. K. P.

[3823.]—SLOT CUTTING.—Here is another Instnnce of amateurs not understanding a drawing, even with a description. The tool figured was meant to be put in a drill chuck or els? In a driller like mine, figured Nov. 12tb, last year, and either it or the work travelled backwards and forwards between two stops to regulate length of slot, and fed inwards tor metal

ll about —In. or lesB during each trip. 1" In 5 minutes

103 is not bad work for a J drill to do, but I do not think the twist form of tool would keep on long at that speed. Mlno was meant for wood, and shown with edges too keen for ordinary metal. I cannot give any time to thissubjeot jnst now.—J. K. P.

[3833.]—FROM " BOAT BUILDER."—J. F. O'Brien does not say whether ho wants a drawing of the whole canoe, or any particular parts. If the former, at lin. to tho foot scale, it would be too largo for our Mechanic, bnt If ho will publish his address I will post it to him. —boat Builder.

r:!833.]—CLEANING COINS.—I flud the following effectually clean old coins so as to read the inscription. First lay them in vinegar, and then rub them with silversand and water— Tom C. Holloway.

[3835.]— CLEANING COINS—J Nash will Bpoil his coins If he cleans them. To decipher an obscuro inscription take a cast of the coin with wax, and a copy of that impression with plaster of Paris. This will show the letters muoh more clearly than the coiu. When a coin or medal is completely worn smooth. If they are heated red hot, say on an iron bar. the original Inscription will be generally quite easy to rend, although the metal of tho coin itself is quite flat.—O..

YOKKE.

NOTES AffD QUERIES.

[3838.]-PRlNTERS- FURNITURE. — Would any reader Inform mo what plane they use in making printers' furniture, especially reglets, and how they are hold while planing them?—A Carpenter.

[8839.]—TRACING CLOTH.—Can ony reader inferm me of a moans of colouring os tracing cloth (such as used by engineers and architects), without injuring the cloth? Also, If there is any substance I could mix with the Indian ink, so as to make the cloth take on the ink more readily 1—Tracino.

[3840.]—MUSHET'S STEEL.—Will anv reader Inform me, through the medium of your valuable paper, how to manage Mushet's special steel, and what shape is the best for roughing tools; a small sketch will oblige. I have tried it many times, and 1 find It too soft'-J. M.

[3S41] - GRINDING DRUG SEEDS.—Will any klnd reader inform me of a cheap and easy method of "rinding drug seeds, fenugreek, &c, on a small scalo? —F. H. H.

[3842.]—STEEL WIRE.—Would the "Harmonious Blacksmith " kindly Inform n musical mechanic, whore to get some steel wire of different gauges, such as is used for gongs In American clocks, or the gongs ready made would suit as well? The querist wishes to make a set of chimes, to be put in a model church, and bells ore too dear ?—J. R. Y.

[38t3]—FLY ROD—Would "ViviB Sperandum" kindly say how he fitted tho end joints on his fly rod, and also where to get wood ana all other materials suitable for same, as I have long been wishing to make one. I hope this will not paBS his notice, as 1 thick it will mterest more than one of us.—Regular

SUBBCRIBER.

[3M4]_ENTOMOLOGICAL QUERY.—I would feel much obliged to any of your entomological readers who would describe the larva of Coimia traprsina; it is said to eat Its neighbours if placed iu the same box with them, which 1 would avoid if I knew lt?-K. N.

[3-SI5.]-BOEHM FLUTE-Can any fellow reader explain the mechanism of the Boehm flute, also what are tho riug holes on clarionets ?—Another FlauTist.

[384G.]-NICKEL, OR GERMAN SILVER-Can a iy reader tell mc what is the composition cl German

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