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grew in profusion on the sand banks. It struck me at the time that these rushes might he collected and made into paper. If so, it would be a beneilt to many. It would benefit Cornishmen, who are in rather low water just now on account of many mining operations being abandoned, and tt would benefit the community by introducing into the market a new material, whicn costs nothing in its cultivation, for making paper. I write this somewhat in ignorance of the quality of the fibre required In the material Tor paper. But I know that the Cornish rushes are tough, and I Bhoukl think would he just the thing.

A West Briton.

KELSET'S PATENT WEDGE-DBIVING DRUMS OB

PULLEYS. - Sir,—Enclosed I beg respectfully to hand you tracing and short description of my patent wedge driving pulley. On reference to the illustrations it will be se*n tflat these pulleys are intended for transmitting power by means of wire ropes, the rope being held firmly between the sides of the palley, and thus preventing a "slip," a ilifficulty hitherto felt by colliery engineers and others whose operations rendered the use of wire rope necessary. These pulleys are extremely simple in construction, and consist of two loose discs, an iuternal wedge-ring, and a boss, or nave, divided in the centre transversely, all the castings being of an ordinary and inexpensive character. Fig. 1 ts a section, and Fig. a a side elevation. The two discs are made with an angular recess on the inner face of each, and the centre holes are cast slightly curved transversely, and made to fit with ease the octagonal bote. The Internal wedge-ring is made with a straight

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point, the periphery being concaved to receive the rope, and. In order to allow for wear upon the latter, the point is also made of less thickness than the diameter of tho rope. The nave or boss Ib provided with a flange cast on each end, which flange is for tho purpose of retaining the disc in position. The nave is faced and bolted together and bored out to fit the driving-shaft, to which it is secured by means of two short keys, driven from each end. The action of the pulley Is brought into operation by means of the pressure of the rope being thrown, on one side of the pulley, upon the internal wedgn-ring, which is thereby forced against the inclined faces of the recess in the discs on the other side of the pulley, the result being that the discs are driven apart on the bottom side and towards each other, so as to compress the rope on the top side.

The practical result of the trial of these pulleys has proved the principle to be a correct one, and, as there are not any parts to get out of order, their use must be attended with considerable economy.

W.m. Kcl&kt. 18, Gannon-street, E.C.

DODS* ELECTRICAL PSYCHOLOGY.

Sir,—Lest the commendation bestowed on this work by Mr. Dineen. p. 91, should induce some of your readers who are interested in these subjects to throw away their money by buying the book, I think it right to say that it is one of the most pretentious pieces of rubbish ever published. Its author is one of those claptrap talkers who pour out streams of high-sounding verbiage without the trace of an Idea; in fact, he is a mesmeric Barnum.

The quotation given, " it will be readily perceived by any one acquainted with electric science,'" &c, is enough proof, for the following statements no such person would endorse; but the Doctor's idea of electricity is the wildest nonsense. He talks about the gold and the chloride of lime in electricity, &c, and describes electricity as the source of matter, and containing in itself all matter, and talks generally with the umul sublime impudence of t lie charlatans who invent systems and Impose them upon others who know just as little as themselves or what they are professing to explain.

As to positive and negative, they are terms only; their value depends on the seDso we put on them. That the human body displays polar actions, like magnets, there is little doubt, and the study of tbis by Reichenbach la a valuable contribution to knowledge, very different from Doa>' assumptions, which are so gross as to destroy the ■value of what he says as to the facts and actions which he describes in common with all other writers on the subject. Finally, J. B. Dods was »o«"the discoverer of electro-biology," but simply a peripatetic lecturer thereon.

Sigma.

A POOR GLASSBLOWER'S QUERY.

Sir,—The readers of the English Mechanic are greatly indebted Mr. Joseph Leicester for his clear description of ^lass-making and staining. I should like to see him give the poor glas*blowers who cannot afford to make new glass a hint or two how to co!onr old metal, say a pot that will hold from half a hundredweight and upwards, a cheap dark ruby from zatiniuin ore and copper, the proportion for a half hundredweight of metal. Also what amount of oxide of chromium would do for a half hundredweight to produce a good colour? Then, is there not a rich colour derived from uranium, lemon yellow? Also s cheap opal from bone ash and carbonate of barytas?

Han Ley. P.S.—I might be able to give him a few colours for glass Inreiuru.

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SEWING MACIIINES.-II.

(Continued from page. 00.)

Needles.

Sir,—The needle is the accompaniment, If not the pioneer, ot civilisation. It is a rare or a make shift thin*: in savage life, and its withdrawal from use would be a sore trial to such tempers as cannot bear the accidental absence of a shirt button. We can purchase a packet of needles for one penny, and seldom think It a marvellous production, or estimate the accumulated skill that has brought this, the lightest and most extensively used tool, to its present perfection.

The majority of the mothers and daughters of England ply their needles at the rate of SO stitches per minute; many, more fortunate, make from 50!) To 2000 stitches per minute by usin at the sewing machine, while others have given up machine sewing in disgust, having selected a bad machine, or having been misled by some vendors who professed the thing could be learnt in an hour or two, and without trouble.

Let the disappointed try again, and be content to proceed slowly, but surely, acquiring first a rudimentary knowledge of the action of the needle, and the shuttle, spool, or looper employed in the formation of the stitch.

Figs. 1, 2, 3, and 4, represent a sewing machine needle

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enlarged. A, the eye of tho needle; B, tho front or long groove; C, the back or Bhort groove; D, the fabric uuder the needle: E, the thread, showing the loop formed under the fabric, and the cloth plate or table F.

Most person.-, on first seeing a sewing machine needle feel surprised at the eye A being near the point, and are perplexed to understand how the thread forma its loop a thousand times per minute. Without grooves in the needle the thread would be liable to be broken on entering the fabric, but laying in the grooves B and C, protects it from cutting and fraying. If it were necessary to prevent the formation of a loop the thread would require to be drawn out faster than the needle, it being double the length of the needle through the fabric; it is this extra length which forms the loop in connection with tho pressing of the fabric against the thread and needle, preventing the thread rising with the needle. The front groove B is large euougli to allow the thread to pass up with the needle, while it is

drawn off at the back, as represented at E. Into this loop the point of a shuttle, or the hook of a lockglitch machine, enters, so that tho whole length of tutunder thread Is carried through the loop; Both aides being tightened at the same instant.

The Lock-stitch.

This application of needle and shuttle to a sewing machine was the Invention of the late Ellas Howe, Jun, of America, whose career as a mechanic is one of the most extraordinary on record. Maturing his invention kept him poor, and then he had to defend his rights at law, finally obtaining royalties from the American sewing machine makers which amounted to a very large yearly income, In addition to the large profits he made in the manufacture of the Howe sewing machine.

Fig. 5 represents the formation of the Howe or shuttle stitch, the upper, or needle thread o, laying on sop of the fabric, and the lower or shuttle thread b, laying below the fabric, the threads being interlocked at o c c c with each other in the middle of the fabric between the four t-tltches.

It is the strongest stitch made, and cannot be ravelled. The stitch being alike on both sides, and using the least quantity of thread, it Is in treneral use, without complaint, unless badly made by an inferior machine, or an incompetent operator.

Fig. rt shows a front side, and Fig. 7 an end view of a shuttle and needle, the arrows showing the direction of their movements when about to pull up a stitch, and they are so timed or adjusted as to complete each one its stroke at the same instant, so that the shuttle pulls forward, and the needle upward, giving a pull of the two threads in like manner to the shoemaker when stitching the sole of a boot.

R is the shuttle reel. After winding the thread very evenly upon It by the machine, it is placed in the shuttle, and kept in a position by a spring or catch so a* to turn freely. The thrcftd iu working off it is directed from the underneath side to a hole in the bottom edge of the shuttle passing outwards, then by n hole adjoining it returns inward, then to holes in tho front end, and to tho outlet holes in the top edge of the shuttle to the fabric. A spriog in the front end of the shuttle at T, with its screw to regulate the tension or strain on the thread, gives the operator the power, in conjunction with a tension on the needle thread, to interlock the threads in the middle of the fabric; or. If preferred, to pull one thread tighter than the other. according to the requirements of the work in hand

H is a part of the ueedle bar, into which the needle is inserted and fixed by ft screw I. In the return stroke the needle descends through the fabric, the needle hole in the cloth plate, and into a slot In the metal K. against which travels the face of the shuttle. If th<-<: parts arc not truly fitted and well polished, the LATHES.

machine will be very troublesome, although the workmanship oí other parte may be very ^ood.

A FiiACTicAL Man.

Sir,—In my letter on the subject of the Saltaire"Warrlour-st. lathe, you have altered my sonse in the 24th lino by inserting the word "cut.*' The cutting would be iho least part of the expense of steel wheels, as, when once forged and turned, the cutting would bo dono with no more difficulty in steol than in brass, only taking a longer time to accomplish. In the elide reel of that lathe there are several small wheels cut out of the solid steel, besides, if I recollect right, a rack for one motion, and a segment equivalent to a portion of a large wheel for another. During the past week 1 have had to cut teeth of fin. pitch, jin. deep, and through caetsteel Jin. thick, which took Ц minutes each to do, so the cutting, alone, or a set of wheel« would not come te very much money, but I am not prepared io say where the necossary forcings could be got done, up to 9 or 10 luche» in diameter, and eoft enough to be out at all. J. K. P.

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я contemporary, may be Acceptable, supplementing as it does that given by "Minnehaha" in your last number. D. V.

"The great drawback which has hitherto prevontod the utilisation of this grass has undoubtedly been the difficulty of extracting the fibre, the manual process being so expensive as almost to amount ta а prohibition of libre manufacture being carriod on. During une last tweuty years or so, a number of machines have been brought out for extracting libre, but none of these have been considered entirely satisfactory. Up to the present time, the common mode of extracting the fibre from such plants as the aloe Is by soaking the leaves in water till the vascular matter has become rotten, and then beating off this decayed matter from the fibre with ft wooden mallet, or scraping it off with a blunt knife. This process is not only a slow and nasty one, but is attended with much waste of fibre; it also discolours, and, what Is most important of all, weakens the fibre. At the London Exhibition of 1802, two American gentlemen, named !<andford and Mallory, exhibited a machine for extracting fibre from aloe, plantain, or pineapple leavee. This machine has been used in America, but would scarcely be found cither sufficiently simple or cheap for the ryots of India, its cost being about tlô. What is wanted is a cheap machine of simple construction, by which the fibre can be easily extracted; and we think it only due to those of our readers who have contemplated entering the competitive list for the above-mentioned priae to state that a machine, possessing, so far as our present iniormatioa goes, «11 the necessary requirements, has already been invented in India by Mr. Donald Gruiksbank, representative of the Telegraph Construction and Maintenance Company. No preparation of the leave« la required for this machine; they are taken to it green, just aa ttrcy ¡ire cut from the bushes, and in the wonderfully short space of two minutes, the fibre in the leaves is brought out stripped of vascular matter, and in admirable condition. The rotting process not being necessary with this machine, the deteriorations in colour, as well as in the slrength and fineness of the fibre which follow upon the adoption of that process are avoided. A correspondent oi an Indian contemporary asserts that the samples from Mr. Cruikshank's machine were "fine, delicate, and even; not one wns cut or broken; and the material would readily fotch £.">u a ton In the home market." Assuming that the efficiency and simplicity of the machine are equal to anythiug that is likely to be set up in competition with it for the offered prize, wo very much doubt whether it is likely to be surpassed In point of cheapness. It is so easily worked, we are informed, that any native may bo taught to nee it in an hour's time, and it« construction is so simple that it спи be sold for 10 rupees (£1 sterling). We hope shortly to be able to give some further description of this machine, which, if equal to the opinion as yet formed of It, from its experimental results, seems calculated to meet a want which ie not confined only to the fibre-yielding plants of Kastern India.

CASE HARDENING. Sir,—If I may, I beg to inform "St. George" (p. 51), that I believe Mr. Armitage's method of case hardening or complete hardening is not only new but that It is the best for engine and machine geariug. During 21 years' experience at some of the leading engineers' such a process has not been adopted. For two steamboat companies and an eminent firm of engine makers, I have oaso hardened the gearing of several pairs of vibrating steam engines, bnt not by the plan of immersion. If the granting of a patent to the gentleman would do him some good I verily believe that it would not do any manufacturer the least :harm. By the process in question, would ¡" St. George " inform me what quaatlty of the prussiate of potash would be required to thoroughly harden a crank pin or a piece of iron of the following dimensions :—liin. long by i In diameter, aud how many times the retort would have to be fed with prussiate of potash before the article would be ready for cooling? R. E T

fitting is the reason for my liking my specimen so little as I do; whereas I do not, on the whole, think it anything like so good as the one 1 call mine, figured October 22ud last year (or Feburary 18th this year, with the addition of a shield for the hatids), which I have been using constantly for 12 years, and cannot suggest any improvement in. The'l-dog-ehuck is the king of chucks for everything above Un. diameter, and mine the bestforeverything under thatsize. Universal chucks, with right au-1 left-handed screw, and 2 dogs ouly, are very well for amateurs, pos-ibly, but are a delusion and a snare, and, I should think, not an effective snare for a practical man. Clements made three ef them, I believe, for his own use, and any one of the three fitting Interchangeably on four different lathes in his shop. I am, as I say above, not a believer in them, any more than 1 am in Clements's driver chuck, which you Hud put on all high-class lathes, bound, as I must be, to admit that Clements was а man of extraordinary talent and, perhaps, the best mechanician of his day. J. K. 1*.

FRAUNHOFERS LINES.

Sir,—I have a grave suggestion for Mr. Troctor's consideration, regarding the origin of the dark lines crossing the solar spectrum. They are generally supposed to be caueed by the absorptiou of those rays from the body of the sun by its luminous atmosphere, which that atmosphere itself emits.

I do not like to be continually at variance in my opinions with the rest of the scientific world, but greatly doubt whether these lines have not their origin nearer heme, aud represent the absorption of those portions of the solar beams by the chemical action established in their passage through our own atmosphere. T. A.

ASTRONOMICAL.

Sir,—1. I should be glad of an oxplanntlou of the reason why, in Dietrichscn's Almanac, the time given between 4he rising and southing of a star is four minutes less than between Its southiug and setting. I do not see what connection there is with the fact that a star sets four minutes later every day.

2. Will " F.R.A.S." kindly tell us how he succeeded with the object glass he commenced some time ago?

3. Sir John Hersohel states that "the total thickness to be abraded from the edge of a spherical speculum 48in. in diameter, and 40ft. focus, to convert it into a paraboloid, is only l-213Mrd part of an inch.'' Bow is this result obtained?

FHANK FOTIIERGlbL.

producing an instrument which, in principle only, was similar to the present. The perfecting of the arithmometer, from its primitive form, was still to be accomplished, and it was nor till after many years of practical experience that it was brought to a atete of efficiency. Indeed, it is only recently that the latest improvements, or what we may call the finishing touches, have been applied, by which its manipulation л is rendered as ca*y as child's play. ^ajsRt]

Although the inventor's first object was to supply the want of his own peculiar sphere (insurance companies). It may be readily conceded that his Idea soou took a far wider flight, and suggested its employment in the various branches of commercial enterprise, in most of which the arithmometer is now employed in France, as also by bankers, philosophers, and men of science, by whom it is found to effect a great saving of time. It is coming into use in Russia and America, but there high prerective, almost prohibitive, duties are a bar to its rapid development.

The instrument is a marvel of rapidity, and those who feel interested can see its manipulation at my office. Since writing the above, I have heard that M. Thomas de Colmar died on tbe 1st of March last, in the 86th year of his age, acting until then as director of the Sun Fire Office.

L. DB It O.ntai.m:Moueau, 1, South-et., Flnsbury.

INDEX FOR DIVIDING PLATE.

Sir,—Allow me to suggest a trifling alteration in the usual arrangement of lathes for ornamental turning, which, however, I do not in any way claim as an idea of my own or a novelty. It. is that the index, or epring point for the dividing plate, instead of being placed, as it generally is, on the near side of the mandTel (that close to the operator), should be fixed on tbe side farthest from him; mine has been in the position 1 propose, for many years, aud though at first it seemed a little awkward having to stretch the hands across the mandrel lor every change of div'sion, I got used toft almost immediately, and soon found the convenience of the new arrangement. The advantages are, instead of the head of the Index coming between the eye of the operator aud the hole into which the point is to drop, as it does iu the ordinary plan, yon look, as it were, under the spring, and have the division always in sight; the light falls much better on the divisions, and, if uecessury, it is easy to throw additional llghton them by placing a piece of white paper in such л position as to reflect lighten the dividing plate, which cannot well be done on the near side.

Though I almost invariably use the index as I have described it, I still retain one in the ordinarylposition, so that, in case of

THE SVNFLOWEn.

requiring unusual steadiness m the work for some special purSir,—When I think of the many uses of this plant, pose, I can use both the indices at and of the Çreat caee with which it is grown, I feel once, in opposite sides of tho surprised tho) It is not more largely cultivated. It mandrel. The upper end of ought tobe, if properly grown, far more productive each index is carried round into than barley, as looa for poultry, who are very fond a curve, and bout back so as of Sub8ow*t seeds, and eat them greedily. This climate to form a convenient handle to is not exactly suitable for the growth of buckwheat, take hold of, as in the accompanying figure.

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the seeds of which are excellent as food for fowls, but if it were suitable, there can be no doubt that it would be extensively grown, and since that is impossible, we may regard tho sunflower as a good substitute. It will do for poultry of every description, and it grows rapidly and readily, almost anywhere; it gives no trouble. I have grown It to a gigantic size, lift, or loft, high, at all érente, with exceedingly large heads, full of hundreds and hundreds of seeds, and this too without auy trouble whatever, and without any manuring or preparation of the soil.

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STAINED GLASS.

Sir,—In answer to Gustavus Knox's question 22:«, No. 261, I have been doing all I can to give' him the information he desires. The following is the result of my inquirios :—There is only one stain used

..,..,, for glass in England, that is yellow. There are ninuy

Tbere are tall and dwarf varieties of the plant, but different shades, but they have all one base-namely, the above-mentioned size, cqualliug In fact the Meli- Mlv,er-, .The flux for silver is antimony ; the silver is anthu» Cali/ornicus, I can only attribute to some >"«'"? in a crucible, when moiled, it looks like a black peculiarity in the soil or in the air. If there be sun- deposit, "d '" put into cleau water from the crucible shine, it will certainly grow vigorously in damp lands, ' then itisgroundaeflneas the finest flour; wUenrequired and it takes up a great deal of moisture, and if planted iol 8tttinme. «"»»" portions are mixed with Vcnetlau on an extensive scale there can be no doubt that It > r?d' °.r comn;,on r»d ochre, which forms a vehicle for would contribute to the health of a place by assisting the ,'lvcr *he ucl're aud »Uver «e ground to the in the destruction of the various miasmata which have СОП8'в<«псу of very fine flour, and by adding a little such deadly and potent effect on human beings. A I »umwator.are made to follow thebrushjust like prJnt saline atmosphere is no obstacle to its growtlTon the !" '" .laid or nowed on the glass according to the design contrary, it grows well when sown near the sea. i rc4u»*d, rather thick; it is then allowed to dry, then There is a considerable quantity of pith in the stalks P1»06«1 In the burning oven; when it has been suowhich I should think might be used to some profitable ! J?cted to- " BTM»,»-»1 moderate heat for about four hours, account, and the stalks themselves, if broken up and '?e Krat,DS oi thc oven Ie pulled ont, and when cold, well dried, form an excellent sort of firewood. The I tnoilv°f!"" "ten in the glass, produced a bright seed is not perishable, and with proper precautions I yellows""», «bile thc ochre washes off with the may be kept a very long time in good condition. !КTM»*" ««ft J' », deep yellow is wanted, the pro

Tho stalks, when burned, yield potash. In ,„«пу ¡ ро"'.оп of silver is Increased, and just as the yellow

BENNETT'S CHUCK. Sir,—In reply to "I. N. G," anyone accustomed to turning knows that a hammer is constantly used for setting work true in all sorts of chucks; this is no exception, bnt It is, perhaps, rather a weak point in this one that after you have got your work to run as true as may be with the help of the hammer, the big screw still waste tightening, which must, to some trifling extent, alter thc setting of thc work. In my description of the chuck on p. 41, 23rd line, the word that being omitted beferc •' the reason," таксе me too willing to admit that defective

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THE ARITHMOMETER.

Sir.—Our old friend, tho arithmometer, or calculating machine (by which all the rules of arithmetic are worked, and calculations of the greatest intricacy, both for financial and scientific purposes, perforuied with unerrlug accuracy and promptitude), is gaining favour In England, as evidenced by its employment amongst the most eminent engineers and leading actuaries, and also iu Government offices; yet its progress here is slow, considering iu merits, compared with what it is in France, which, it should be borne in mind, Is the country of its origin. This restriction to Its usefulness is doubtless in some measure also due to the inventor not being, like many inventors, a needy man, and leaving tho instrument to work its own way.

In bringing out the arithmometer, M. Thomas de Colmar proposed combining cheapness with simplicity of construction and portability, a problem which, at that time (nearly thirty years since), appeared of doubtful realisation. M. Thomas de Colmar, however, applied himself to the task with the energy of a man determined to conquer all difficulties, not tho least being his ignorance of practical mechanics, and bydint of time, labour, aud expeuee, he succeeded in

are produced by using enamel. The enamel is ground very Hue, just like paint; a largo slab of glass or iron Is used. The ground enamel is placed upon It, and a large glass crusher is rubbed upon it by hand nntil It can be worked just as paint is worked. The flux (glass and red -lead) is also done the same as the enamel; both are worked to form u substance of the consistency of pafut, aud,when painted ou the glass, a» required, tho flux leaves the enamel to melt in the window-glass, aud produces the beautiful colons* referred to. There is great art in the burning of the colours in the glass; Succcbs is ouly attained by long practice. The glass itself is so various in its nature with regard to being hard or soft that only those wbi> by long practice in the business have come to understand these things are fit to become glass staine.rs. Jos. Leicester.

ROTARY ENGINE.

SIR,—I have noticed several specimens of rotsry engines in the English Mechanic, and 1f you think this worthy of your notice, I shall feel obliged to you for Its insertion, as it may be of «se to some of the readers of the English Mechanic. It is called Hammond's rotary engine. A, Fig. 1, is the outer box, which is stationary, with the end or side plate

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©IT. showing tbe interior; В the iiiner box, which

revolves; D pipe lor conveying the steam to the

cylindert G waste eteam pipe; F a eliding plate

through the outer box; Ea spring to keep the plate

elote to the inner box. ЛУЫ1е revolving, the steam

en ten at P and make its exit at R, whereby a rotary

motion is obtained without compressing the steam

;tgain Jn the engine before It can make i te escape,

which Ы the casein most rotary eugines. Philip.

SLEEP.

Sir,—In your issue of April 8, I find a scrap of information at the head oí the section of your paper designated "Chips," which 1 should like further information upon. The passage reads as follows :—"M. Sommer propounds a new theory of sleep; hie idea is , that bleep is simply a result of the deoxygenation of the system, and ho believes that sleepiness comes on ал boon as the oxygen stored inthe blood i* exhausted." In the first place« 1 should like to know who M. Sommer le, and in what particulars hie theory differs from the popular theory. The fact is, I very much desire (by your permission and through your invaluable paper) that the subject (sleep) should be thoroughly ventilated—¿л, come to some conclusion, scientifically, M to what sleep is, and what is the cause of sleep. .Personally, I should be much obliged if any one of /our numerous correspondents could point me to a good work on the subject. Coma.

GEOGRAPHY AND EMIGRATION.

Sm,-There are two reasons why I should be тегу carelul wheu writing anything for iusertion in the Km.i. Ilh Mechanic. The first of these Is, that your space is very valuable, aud, therefore, it is desirable to »ay what we mean in as few words as possible. Secondly, my time is limited, and upon this score fancy must never be allowed to roam. Too have kindly intimated that space is at my disposal to give epitomised accountsof tbe transactions of the Royal Geographical Society. It has struck mo that whilst Uoiug this I can be of much more service to vour readers, and supply a vacuum in our periodical literature. Emigration la, and has been for a long time, a standard topic for conversation and debate throughout the length uud breadth oí the country. There are questions—and are very difficult ones to answer— which arise upon the first thought of emigration. Wheu shall i go ? What 'ïountry or colony am J most suited for? To answer ШМЦ questions it is necessary to be acquainted with tlie various natural characteristics of the colonies, «be, open to emigrants, their climate, launa, flora, &c. Now, Sir, backed up by tho splendid library of the above-mentioned society, I think it your readers who wish for some instruction regarding geographical matters will kindly forward queries to you in 'he ordinary way, embodying in them their special re'¡airtruienta. 1 shall be enabled to give the information required at an early moment. F.R.GS.

from the weather U very picture-quo, but is a great evil, as it harbours earwigs and a host of enemies to tbe bees ; an oldcracked red basin, or, in fact, anything but straw, to keep the wet off is all that is needed. Besides, these straw roofs are generally fixtures, and then the Impossibility of taking the honey without killing the bees. All observations, and as much of necessary work as i$ possible, should bo carried on in the year. With quietness and self possession, tho bees will never stieg. I will add no more.

Ok eis A Beekeeper.

BEES.

B Sl*.—As I see a proposal to have space in the KNoLftB H ten ¿к ic for amateur farming, I would, in the event ol «ich. spice being given, say a word on profitable h«e-keeping. I learnt my lesson from ths aged apiarian, Mr. Payne, of Bury St. Edmunds. He always asserted that it should be made a paying business; andif.onatj outlay in thespring of 10s., one hive will, as fs often the case, produce Ittfb. of honey, and more, it would go a long way towards paying the rent. Mr Payne, although having all the new inventions of his day, yet adhered a« a rule to the flat-topped straw hive, with »hole 4m. in diameter on the top. which we plugged ap In the winter, but which in honeymalttag time was taken out and a smaller hive of ►traw, or a bell glass, oran old tea-chest, placed over Il In a " cap." as it is technically called, of the latter kind, I have myself secured 16U>. of honev in a few weeks. The hive itself should not bo fastened ou its stand by mortar; we muy leave the bees to do that; tuey will doit effectually. A straw roof to preserve

THE "PHANTOM" WHEEL.

Sir,—Will you kindly allow me to ask those of your readers who are not yet our customer to suspend their judgment for a week, alike upon tho claims and the condemnations put forth in the modest letter of Mr. Edmund M. Т. Ту dem an, which appeared in your last issue. Pressure of business of other kinds, and the very limited time within which I uaderst&nd you will go to press with your next number, prevents me from now dealing with the subjects.

J. A. Mays, Secretary and Manager, Phantom Vcloce and Carriage Wheel Company.

DR. KITC HENKK'S TELESCOPES.

Sir,—I am glad that an inquiry for Dr. Kitchener's telescopes hau been made. 1 hope that some of our mauy readers who are interested in astronomy will be able to answer the question.

The author of "The Cook's Oracle" had. for his time, one of the finest Collections of instruments In England. No expense was spared by him in the purchasing, and no one knew better how to preserve the objectives from injury.

i am therefore Inclined to think that wherever they now are there must be some of those fine treble objectglasses made by Peter Dollond a hundred years age.

I have heard the work done then was superior to much for some timo afterwards, though, I have no doubt, inferior to the productions of our best artiste of the present day

Still, я great interest attaches to these telescopes. It is well known that pome fifty years ago Sir John Herechel published his formula; in the " Philosophical Transactions." And he says in 1861 that they still are generally the tables used by our best opticians. But when Dolloud made these triple object-glasses, no tables practically of any value were in existence. I suppose he found out the curvatures by successive trials.

Mr. Webb need not be afraid that we ^hall be weary of his "Hints." Anything from the author of that delightful book, "Celestial Objects for Common Telescopes "—a book which has made more astronomers than Any other in the English language—will always be received with pleasure.

Will any of у ma readers kindly state tho smallest aperture with which they can see tho cöme* to Rigel? 1 have found "-'in. show it well when the night baa been by no means good.

I entirely concur with "F.R.A.S. " in thinking that 41n. is the very smallest objoct-glas« which will pick up six stars in the trapezium.

1 am glad lb.« namo of Mr. Wray has been lately brought forward. 1 have seen some fiuo work done by him, and his prices aro extremely moderate—which just now ia a great recommendation. Stella.

EXTRACTS FROM CORRESPONDENCE.

A GOOD SUBSTITUTE FOR BINDING SCREWS. — E. C. Murray writes as follows :—'* 1 send the following, thinking that It may be «f service to those of your subscribers who have, or are about to construct bat trie* in which " carbons" are used. Bore a hole in the top of the carbon $in. deep, and about ¿in. in diameter, scrape it out towards the bottom so that it i* rather larger than the top; procure n piece of ■tout copper wire about Sin. long, bond the end,

thuH, j make the end of carbon hot in a clear fire

tsfce Hout. place the crooked end of the wire in it and fill it inround the wire with some solder (which should be melted in a small ladle). Of cour«e the other wire mny be soldered to the zinc. To connect the butteries. I clean and lap the ends over ^in, and bind them with some fine copper wire, which must be clean.

THE I! ENGLISH" VELOCIPEDE.-*'Over Sixty" says :—" Living in a country where there are many hills to mount, I am always looking out for a three-wheeler that will really go up nlll. I want one for use, and not for mere amusement. It strikes me that the arguments of 'A Thinker'in favour of the front guiding wheels bearing the load are good, but the principle of his machine seeme to meto be precisely similar to the * Edinburgh'velocipede, manufactured by Mr. Brown, 5?, St LeonardV street, Edinburgh, the latter having a much lighter appearance on paper than ' A Thinker's.' The * Edinburgh' weighs from fillb. to flOJb., but In the drawing of the ' Edinburgh.1 although evident that the guiding apparatus is on each side, it is not made plain what tho contrivance is. The driving wheel behind is higher than the two front guiding wheels."

REPLIES TO QUERIES.

PRESENT STATE OF OUR KNOWLEDGE OF METEORITES.—Herrr Iiammeleberg. of Berlin, has Jii4t given a summary of what is known, from a mineralógica! and chemical point of view, of the meteorites, those mc-sengers from other heavenly bodies which from time to time reach our enrth. The essential constituents which are always present in very distinct classes of these foreign bodies are nickel, iron, phosphorus, sulphides of the metals, oxide«, silicates, free silicic acid, and, in rare instances, carbon, or combinations of carbon. The saine subject is treated at great length by M. Daubrée iu tbe Journal <fes Sarotitx for Jan., Feb., and March.

[1875.]-ANGLE IRON HOOFS.—" N. B." can fiud the length of angle iron for the hoops, by adding six times the greatest thickness of tbe Iron to the circumference of the hoop, which can be found by using the rule given by "Leo L," p. 610, Vol. X-, and for the length of the Iron for the hoops, with tbe flange on the inside, subtract six times greatest thickness from the circumference of the outside diameter. In the two hoops that he gives, first one, 2ft. dlam. inside, with flange on the outside, circumference 2ft. = 75-;tin., add i>!ii:. which is about six times the greatest thickness, and it gives ВРЗМд. - oft. i*j{iu. for tho length: the other one, 2ft. dium. onteide, with flange e-a the ineide, subtract ein. from To .'lin. = Ю-ДОо. ■= 5ft. Ofiu. This rule was given to me by a foremau boiler maker.— Scire Volo.

[2000.]—PROBLEM.—In the flret number of tho present volume, there are solutions to my query, and the result in each case is. that "the difference between P and Q is equal to half the difference between the weights of the arms," which is not the solution asked for in the query. As the answerers of the problem doubted the correct copying of it, I wrote to or three weeks ago, informing them of its belog correctly taken from M Tod hunter's Mechanics for Beginners," chap. XII., sum 12. As my answer did not appear in your pnper, I presume it was overlooked, and I again beg to thank " Franck " and others, who solved the problem, and should be glad to know whether the sum or the answer is worded ¡нсоггссОу in " Todhuntcr'e " book. —Y. P. W.

[21430-SOFTEMNG CAST IRON.-" Blue Ruin" is in error when he states that "G.B.K" cannot ■often cast Iron. Пе can do so by heating the metal toa bright red, cooling quickly in water, reheating, and then annealing by cooling slowly in ashes.—J. B.

[2153.]-VERTICAL SAW FRAME.—I doubt very much that " J. T. W." would ever get a frame to cut his oak logs, unless he went to an enormous expense, that is if the timber is English oak, at such a place as Sunderland, for wood ship building. I never knew the English oak cut up with the frame, unless it was pretty straight along tho bottom, or was first sided up on two sides,—Mill Sawyer.

[2184.]—SULPHATE OF LEAD BATTERY.— ЛУШ "A Good Boy " please sny whether he amalgamated the zinc plates to his battery, and will some experienced contributor inform me if it is better without .'—plume. SuLpn.

[2223.]—ENG RAVING ON SLATE.—I sec two correspondents giving advice on this, but 1 doubt the querist will be much aided by it. I have out some thousands of letterson slate, and my mode is, draw iu the letters wiHi a btacklead pencil, if wanted very accurate, comeoverwlth a draw point, taking asquare graver, cut a deep bold lino up the centres of the letters; this line if done with one cut will be broken and jagged at the edges, then take a flat tool (a tool about a quarter of an inch broad, and sharpened exactly the same as a joiner's chisel, but mounted in a graver handle), and with the flat side to the slate, cut from the centre stroke to the outside edge of the letter, holding the tool so as to cut the outelae of the letter bevelled; it cuts as clean us a bit of cheese, the letter wheu finished bemg deep in the centre and bevelled olf to either side,—I. N. G.

[2233.]-STAIN ED GLASS.—See answer by Mr. Leicester among tho "Letters to the Editor.'*—Ed. EM.

[22S6.]-DIRTY CEILINGS.—Only ceUlngs.the outer portions of which are exposed to the iutluouce of temperature, have the "ribbed" appearance. Iu d»'np weather the plaster absorbs moisture, tho dust mod smoke adhere to tho ditnp portion; the joists keep the planter dry, hence that portion Is less dirty aud smoke-staiaed.—The Welsh Shkpiiehd.

[2263.]—AMBKR.—Amber is soluble to a certain extent Ш alcohol, ether, chloroform and turpentine. ~ Beta.

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[2J70.]—JtOTIOX OP WATER.—38 x 2 5 = 95 depth of wator in feet, .yas x 81 = 78 5 the velocity of discharge in feet per second ; diameter of orifice lin. a '005KS; the area in square feet

78 S x -005« x 60 = 257 cubil1 feet discharged per minute.—Antiiont.

[2ЛО.] —NICOTINE. — "Mnuee" should put two drops of oil of eassafrae on his pipe of tobacco, which will entirely prevent vertigo, and all the other disagreeable effects of smoking.—Viatoh.

[Ш1.]— THEOREM.—It seems to be a particular case of the theorem "the circle is greater than any isopcrimetrical Usure," which is proved in several authors.—A. BbANcutT.

[2296.]—DIE.—I think "Cantab" л-ould have a great trouble to cut a good counterpart to his dio with tools. A much better plan would be to stamp a copper counterpart with the steel die itself, provided it Is hard enough. If itis not, lie must harden it by one of the many recipes given in these pages.—W. II.

TlIOHPE.

[U2070-VIOLET INK.-Boil4oz. of logwood in 1J pint of water to one-half, strain, and aldrtdr. of gum nod 1 In/, of alum; set aside for 1- hours, and decant for use,—Beta.

[Í30í>.]-ETCHING ON GLASS.- To etch on glass with fluor spar, cover the glass with beeswax by melting the wax and runningit over the glass, about 1-lBth of an inch thick, then write ou it with a needle after which sprinkle some*fluor spar upon tho wrlttn?. and pour sulphuric acid on it, let ic stand for 10 or 12 hours, then wash off the superfluous acid, and take oft the wax and wash the glass clean, and it will be seen that the fluor spar has eaten away the glass on those parte not protected by the wax.—Psactk-us.

Г2331 }-PATENT DRYERS.—The mixturo is considered a secret, bnt the following may be the material cliiefly employed :- l'roto sulphate oijlron (green copperas) is put in a cleau iron pan upon a clear low fire, when melting, stir about aud evaporate to dryness oaly. This substance, ground in oil, acts as a dryer. Sugar of lead, ground in oil, is the best dryer for delicate tints. Litharge is the most active (iryer of all, but can only be used for dark colours, as it discolours light and blue tints. All oxides are dryers, as a general rule—Tiie Welsh SiiLriiF.ru>.

PS-TÜ]—UNNOTICED QUERY,—The traced patterns for embroidery are printed, when many copies of the f-ame pattern are wanted. If a dozen or two are only required, the patterns are made by band, as followe :—The drawing is made upon paper, lay the drawing upon au even cloth, and perforate ail the lines with a tine needle, close and even. >fow take finely powdered charcoal three parts, resin one part in fine powder, mix and tie it in a piece of porous calico, so that it forms a dusting bag. Lay tho perforated drawing upon your material, hold down with one hand,rub the dusting bag over tho drawing, the dust falls through the hole», and forms the drawing on the material, remove the paper drawing, lay blotting paper over the dust pattern, and go over it with a worm flatting iron ; the heat will melt the íesin and fix the drawing en the material.—Tin Welsh

SlIEr-PHERD.

L2341.]-CANOE,—From " Oversnnds' " query I suppose he wants a ship for cruising, if ю, the dimensions given will furnish what he requires :—Length over

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all, 15ft; greatest beam, 2ft. 2in.; depth, tees ksel, itin.; rise of deck. Sin. This boat may, with the exception of ribs, carline, und risings, bo built entirely of pine, which should be fresh cut from the balk, as it will then be easier to bend and \m& liable to split; or if "Oversande" prefers, the keel can be made of ** ' *• • *

oak or American elm. and the curved stern und stern pieces of oak, the ribs of chestnut, steamed or boiled till soft, to be fixed hot, as they set in cooling, and will not alter in shape when unce in; keel, allowing for scarplis ubous 13ft. long, ijin. deep, llin. wide, to have a rabbet worked on each side and up the curved pieces (as high ae boat is to go), where the rabbet flattens. Fig. 1, section of keel midships; Fig. 2, method of scarphing cutwater to keel; T, places for screws, which should be bras«; Fig. similar», through л b; Fig- 4, half of main section,

3, section of stem (я torn is

Íin. to the foot. Л board should be cut out and boat built up to it.—Maty. t

[2324.]—GYMNASTICS.-Let"Gymnastikos"char the ends of the posts that are let into the ground, and they will last a very long time indeed; another plan is to steep them in crcosetcoil a week or во before putting down,—Mill Sawyer.

[23ilAND2355.]-CANOKS AND BOATBUILDING.

— I nave seen several Inquiries on this subject, and had hoped that some abler pen than mine would have answered them. For the benefit of canoe builders I give below the dimensions of tho Rob Roy class, лч published by the club ¡—Length over all, 14ft., beam outside, 20In.; depth from surface of deck at fore end of well to top side of keel lliu.; keel to project lin. outside, and to have lin. camber or round in its length. The beet material for wear is English oak cleaned up to 5-lutbe of an mch thick, but for lightness, white h'r or white or yellow pine are used. In answer to "C. D. R." the'keel should be of oakorAmerican elm; the timbers or ribs of the same, or ash; American elm is the best in my opinion. The stem and sternpost are worked of oak grown to about the right rurve and scarphed to the keel. In building, the strakes or planks are worlced first, and then the timbers are steamed and bent in and fastened while hot I shall be happy to furnish sketches of nny parts required, or to give any information In my power on this subject or yacht building to any who may think of attempting this pretty art.—Boatbdilder.

[23W.]-GEOLOGICAL MANUALS.—Having regnrd to the limited prices, there are only three published In England—Jukcs'e, Houghton's, Page's, the publishers are knowu to all bookseller». I will now pass my opinion on these; they are all good works, but the ground of prctereuce must depend on the student. If he likes a book that has "grit '* In it, technical and directly, ad rem, and is not afraid of a hard book, let him buy Jukes's; I like it myself, because conceited enough to undervalue popular works in the popular style of science. If something easier and more diffuse would suit, why then order Page's 'Advanced Text Book;" the other, Houghton's, пае peculiar features of its own; does not so much allude to English examples; has a good deal to say about distribution nf the organic Ufe on the globe, the orders, their first appearance, and their extinction; takes a glance at the " plasma " of the earth's crust, and such like physical theories, and is Irish in reference to examples. It would not hurt a student to buy, at intervale, each of tho works named. I could give advice as to an early course for a student, but to do so iffectually I should require to know something of bis previous education, his means, hie opportunities, his locality, Ac. Perhaps I may put together a few hints on the subject for the English Меспамс, at no distant period; moavwhtle, I advise the student to hang on to the skirts of tho nearest practical geologist he can meet with. Publishers: Jukes, Black; Page, Blackwood; Houghtou, Longmans.—F. S., F.G.S.

[2346.]-GEO LOG V.—Ono of the following works might suit:—" Pace's Textbook," price 6s., Blackwood; "Jukes's Geology," price 12s. 6d., Black and Co.; "Phillips's Treatise," price 7s., Longmans. — Beta.

r23C2.]-COPPER 8MELTING. —In answer to *' E. V. D. S." I am not aware of there being any copper smelting establishment in Loudon.—T. Ros

KELL.

[236.3.1-8ILVERING BRASS.-In answer to " Poor Clock Jobber" respecting silveriug braeswork or clock dials, the following is the method used formany years to silver the clock rims or lusido bezils :—Gd. of pure silver dissolved in half a teacup of nitric acid, the solution of silver to be carefully washed to free it from the aeid; afterwards to be mixed with Id. cream of tartar; when the tartar is mixed add half a brick of common table salt, pounded line, the whole to be well stirred together. The articles to be silvered muet be dipped clean in aqua fortis, or scoured with line sand. The part to be silvered must bu rubbed with a clean cork dipped in water, then in the silver powder. '1 he whole to be rinsed iu lukewarm water, and dried in clean box sawdust, and then be varnished with copal varnish mude thin with turpeutiue. This lean old method. The modern one is to laquer the work with colourless lacquer.—J. M., Birmingham.

[2371.]-HEATING OF JOURNALS.— If "Reiwot" were to remove the brasses from his heating journals, and replace with hard wood, and state the result in the pages of the English Mechanic, it might benefit others as well as himself. It is best, if possible, for the wood to be endways of the grain. I was iu a very large windmill last week, where the lower end of tho wind-shaft was working against wood, but in this case, the wood woe strongly bound by an iron band, to prevent splitting, ae the pressure woe very great, and brass had been removed oa account of heating; it has been at work thus for many years. The necks of all the stone spindles in the mill, four pairs, are working with wood instead of brass in a satisfactory manner.—R. N. Smith.

[2371.]—HEATING OK JOURNALS.-" Relwot" should apply clean soft soap, let the neck revolve in this a few moments, then pour on common washing liquor, which will fetch out the dirt. Repeat if necessary. This can be done without stopping the engine, and has often proved effectual.—Mutual ImproveMent.

[2371.]—HEATED JOURNALS.—Heated journals in many с a* es may be cooled by pouring a mixture of antimony and oil frequently on them. — Vivís Sperandum.

[2376.]—GEOMETRY.—The following is perhaps the easiest method of solving this rather long problem. First of all determine by its traces (H T and V T) the plane inclined 00°, assuming this plane perpendicular to the vertical plane of projection ; next determine by its plan and elevation, a perpendicular line to this plane; then a plane containing this line, no matter in what position, must be perpendicular to the given plane. To determine the position of the second plane (70°), make the point О (where the line intersects the plane), the apex of a right cone, whoso slant edge is inclined at 70". All tangent planee to the slant sides

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perpendicular to the 'plan of the line of Intersection of the other two plunee. Then, if we draw a line» perpendicular to tho line of intersection, and passing through the horizontal trace of the perpendicular line*, we have the horizontal trace of the third plane, and a line drawn through А О will be the plan of the second line of intersection. The third line i« drawn from О to B, then having got the horizontal tracée and one of the venical traces, it is an easy matter to get the other two. The inclination of the third plane is got by making an elevation on a ground Une, perpendicular to its horizontal trace. Driw if \f perpendicular to H T3, and project the point О perpendicularly through x' //, then set up the height of the point O' taken from the other ground line U y), then a line с f, drawn through this point, and the intersection of the trace with the jef ¡f will give the inclination required, which 1в46з.—M. Wheat-ley.

[23*0.]-MERCURY BREAK FOR COILS.—«' R. S." will find a description of a mercury break In the appendixof '* Chambers's Eleotriclty," by Dr. Fergason. It consists of a vibratintr spiral of copper wire. Another form is given in Du МопсеГа work on the induction coll ae constructed by Gaiffe. which, like the ordinary epring break, derives its motive influence from the core of iron wires. 4t ie constructed ;ae follows:—A braes pillar with a slot cut in the top carries a lever of soft Iron eomc ftin. long, one end of which terminates In a cylinder like that of the spring break : the other end has a wire depending from It tipped with platinum, which dips into a cup containing an amalgam of mercury and platinum, or mercury and silver (which is cheaper and more easily made); the iron lever ia centered in the slot by means of a pin passing through it, so that it can slightly oscillate in the vertical plane; a epring bent la the form of an arc ie fixed to the under part of the lever, which, by means of a rack adjustment, can be made more or lese tense, so ae ty accelerate or diminish the rapidity of the oscillations. The ÍHilar is of such a height that the cylinder end of the ever, when at rest, Ie about ¿in. or Я-loth in. above the endof the bundle of wires in the coil. The mercury cup is capable of being adjusted to any required height, so that the platinum wire just touches the" amalgam ; over the amalgam ie poured some alcohol, which, being less conductive thau air, renders the

Çaesage of "the extra-current spark more difficult, he pillar and the cup are respectively connected with the coll in the same manner as the two sides of the spring break. This form of contact-breaker if chiefly applicable to the larger clase of coils, especially when used with great battery power; ae before stated, it renders more difficult the passage of the spark of the extra-current, which so rapidly oxidises the platinliini of the spring-break; moreover, for the same reason, it elongates the spark of the secondary wire. Гц a coil I recently made, the spring-break, with 3 Grove's cells (5in. x Sin. of platinum immersed) gives sparks tiin. long ; the mercury break, with samo batterypower, gives sparks 7in. The mercury break is, however, not adapted for illuminating vacuum tubes.— J. D. M.

[2381.]—FIXING IRON STANDARDS IN STONES.— The composition generally u».;d for fixing iron standard* in stones for wire fencing, ratlings, &c., is composed of brimstone (crude sulphur) and washed dry sand in about equal pare, poured into the ioiut in a molten Btate-—

VlVHi Sl'BHANDUM.

[2384-3-WORK ON ELECTRICITY.—I should recommend "S. T. P." to purchase either "Noad» Inductor I um," price 3s. or!., or "The induction Coil, How Made, and How Used," by Dyer» price Ie.—F

RUSSELL.

[23000-INDUCTION COIL.-Thomae J. O'Connor may safely use a battery consisting of 6 or8 Grove's or Bunsen celle (pinta), or 3 quart bichromate celle.—F. Russell.

[2300.]—INDUCTION COIL.—T. J. O'Connor asks what battery power would bo suitable for hla voll

J

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If his roll is well insulated, he can use a bichromate battery, presenting a total surface of 48 square inches, or one quart Bunsen's battery, with about «fi square inches. Such a coil with a condenser of 25 sheets. 0 x i, ought to give Jin. spark at the least—A. K Tucker rj>3t».]-DIE FROM MEDAL.—The best way for ** Medal " to procure a counterpart or die from his medal would Be either to make a mould iu plaster of Paris and cast It, or else, which lit the better way, to reproduce it by means of the electrotype process .—F. Kcmell.

f24W—FLUXES.—In reply to "Dorset." he can obtain floor spar from any of the mining districts of Cornwall. I get mine from Redruth, though one of tbeassayers. It can be bad In powder from almost ail drysalters and dealers in chemicals. J. J. Griffin, 22, Garrick-street, Covent-garden, London, supplies it; white argol may also be had at the same place. White argol Is the commercial nnme for crude bitartrate of potiusn; cream of tartar is the same, purified; tnrtaric acid is also obtaiued from it. It is chiefly obtained as an incrustation iu wine casks.—

"1". ROSKELL.

[2404.]—TELESCOPE QUERIES.—I nm unable to answer the query addressed to me by "C. S.," page 6'J, for the following reasons. 1 do not possess an eyepiece of the power he mentions—the highest I hare used is about 300 ; also my telescope was left behind in Manchester, and I fear that I shall not be able to send for it before the middle of June. One point is worthy of notice, the stand seemed almost perfect on quiet nights, but If not sheltered, the instrument had an unpleasant tendency to come "head to wind," so amoothly and easily did it work. This will be remedied when I get to work again, and I think it will then be the best possible form of stand for an altazimuth.— Arthur W. Blacklock, Newbridge, Aberdeen.

[2-407.]—DYEING.-"Mordant"will get the fullest information about chemical dyeing in "Musprat's Chemistry,''but it is a very expensive work. "Napier's Handbook on Dyeing" may suit him, it is more mechanical (if I may use the expression dyeing than ■ -hemlrai, but contains a multitude of recipes for <1yeingcottonand silk iu all colours.—Vivis Spexan

DL'M.

[3414.]-ALGEBRAIC EQUATION. —Let x = greater number ,\ x — 2 = less number, Then

x (x - 2) (2x - 2) = 12 or

x (x - 2) (x - 1) = o

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and the less number = x — 2 = 1 Or

+ J - 3 - 2 = (V - 2 - 2)or - (V ~^ 2 + 21 —J. f. P.

[2414.]—ALGEBRAIC EQUATION.-" Pater " will find the following to bo a correct solution of his problem .—Let Sr = the greater number, and r = the less; then <3x* x 4n = 12; or, 12j-> = 1.'; dividing by 12, x»= 1; extracting root, x = 1; therefore, 3.7: = 3 Proof:—,1 -1 = 2, the required differencs ; (3 x 1) x <3 + D = 3 x 4 = 12.—W. Airey.

[2410.1-ADHESIVE MATERIAL.-A thick mixture of dextrine and water possesses great adhesiveness. Dextrine, or British gum, is made by exposing potato starch to a temperature of 400°. It is a cheap article, and largely used as a substitute for gum — Beta

[24200-SPR1XG BOW.-A steel spring bow of given length cannot be weakened except by reducing its substance tn thickness, or otherwise—J. B.

B»23.]-AQUAR1UM.—Why docs not your correspondent use gas piping? I have used It continuously for several years. My lishes lived and got fat, yet I never fed them, but kept the aquarium well stocked with vegetation. I have found no cement to Burpass Portland cement, it hardens under water, and makes a good artificial stone.—Country GnocEF.

[2423. J—AQUARIUM.—Giitta-percbn does not affect water in any respect, neither fisli or any other thin" will be therefore injured by water which has passed along pipes of that material, Roman and Portland cement are suitable for uniting rock work, and can be obiained by any mason; but both of these, and the lormer especially, give off an efflorescence for a time which is poisonous to iish if the water gets imnreenated with it.—J. B. h

[2424.l-MiCROSCOPICAL._The Quekett Club publi.hes a quarterly Journal, which is supplied to its members free of charge, and which contains reports of the proceedings of the club, and in which the most important of the papers read at the meetings are published in full, with Illustrations, when required. A member uuable to attend the meetings could scarcely demeany advantage beyond the perusal of the journal ; but any subject he might wish to bring under the notice of tho club, with a view to elicit opinions, or otherwise, would receive attention If brought forward »~r".?i 'he "ecretary or any other member. As a re?u ,\r attendant at the meetings of the club, I should iSJSSZ. J?,0' BerTice iu tbj8 w"y to <TMT atTM*" hLT.h i KN«Uo» » K«l«tin« is largely used, and can z.£.TMJ. 1'ev-of almost any grocer. With Cox's I am not acquainted, nor have 1 ever known isinglass to be used for microscopical purposes.—W H G

elSSS&L^gl ST1TM-866 "J- K' n" leUer

.-i!?*43iLr^,t,P^TIN'} LARGE CYLINDER.i .5!*° . had better have wooden caps to fit the ends of bis cylinder, with brass bearings screw tight in trie centre of the caps, and secured by a lack-nut Inside and varnished with sealing wax varnish I Have one that is done the same way, aud it answers well.—J. M.

[2448.J-PLANET NErTUNE.-Adams's calculations and formula first appeared as an extract from

the appendix to the " Nautical Almanac " for 1851.— Henry W. Henfrey, M.N.8., Ac, Ac.

[24.->0.)-FASTKNlNU PIN TO BROOCH. — In answer to "Yorkshire Bite," he must use shellac to fasten the pin or jolut in his brooch; this is what the black ornament makers use in Birmingham. Tbs joint is warmed previously to putting together.—J. M

r2455.]-FREr CUTTING ROLLED BRASS.— "Chip" had better use coarso cut saws to pierce his Jin. brass with, aa the fine ones get hot, and then merely rut, not cut; ho must lubricate with a little suet or wax, and not work his saw too qnick. I hare cut some metal 4 thick, for book mounts, and I found fine cut saws of no use whatever. Perhaps he would let me know how he succeeds in his next attempts?— J. M.

[2450.1-OLD COINS.-The first-mentioned piocos of " Sbahazadab." are merely Nuremberg tokens or counters, and are of no value. He will find many particulars relating to them in the last volume of tho English Mechanic, see pages 309, 537, Ac. The following is a description of the " Vboo Popull " halfpence. Obverse, a laareated head to the right, the neck being bare. Legend; VOCE POPULI. Reverse, a female seated, looking to the left, holding a brunch in the right hand; a spear, pointing backwards, is supported bv the left arm, and behind the figure is a harp'; HI HERN'IA above, aud the date, 1760, below. There are a great many minor varieties, which 1 need not notice here. I extract the following from the "Numismatic Chronicle :"—" For some years prior to 17B0, very little cepper money was struck for Ireland, which caused such a scarcity of small ohango that all aorta of base stuff was cast into pieces that passed for halfpence and farthings. This gave an opportunity to a Mr. Roche, of South King-street, Dublin (who struck metal buttons for the army), to issue copper halfpence and farthings, which were generally received in preference to tne wretched sort then in circulation. The first sort he sent out was badly finished, and on one side a head laureate, looking to the left, and for inscription, VOX POPULI; reverse, Hibernia sitting on a globe, holding a laurel branch In the right band and a spear in the left, with HIBERNIA round; in the exergue the date, 1760 (none of these sort are now known to exist). The second sort that he issued was much neater, and better copper, with the inscription on the head side altered to VOCE POPULI. Tbo halfpence were a larger size, and done in the same manner. However, on information being given to the then Lord Mayor of Dublin, the whole apparatus for striking the aforesaid coin was seized ana lodged tn the tholsel. Roche fled from the same." Tho most comprehensive account of these curious pieces is by C. Clay, M.D., published in Part III. of the" Proceedlngsof the Manchester Numismatic Society," 1866. The medals in brass of Admiral Vernon, are very common, not being worth more than Is. I havo two specimens in my cabinet, commemorating the takiug of Porto Bello — Henry W. Henfrky, M.N.S., Ac, Ac, author of .a "Guide to English Coins."

[2456.]— OLD COINS.—The one figured is a Nuremberg token. The words " llaus Krauwlnkel, Nur."are very legible— Bernardin.

[3456.]—OLD COINS—Is a counter or jetton; made by Hanns Krauwinxel, whose name appears on the coin. If " bhaazadah ' will refer to " Snelltng's View of the Origin, Sec, of Jettons or Counters," or even to the English Mechanic, a few weeks back, he will fiudall. or as much other information he may require. The " Voce Popull." or "Pretender's halfpenny." as ir is sometimes called, was struck iu Irelaud iu 1760. It is rather smaller than an ordinary sized balfpenuy of the period. There are conflicting accounts of its appearance as a singular and distinct coinage, and it is singular that its origin Bhould be lost in obscurity, considering its comparatively recent date. The various authorities ou the subject are brought together and printed in the "Proceedings of the Manchester Numismatic Society," Part 3. There Is a variety with the letter P in the front of the bust, aud another with P uudor the bust. There is also a farthing size The Vernon medal was probably struck on the taking of Porto Bello. and I dare say some of our medal collectors will send information.—D. T. Batty, Fennellstrcet, Manchester.

[2457.]-TEA CHESTS. -I would state that it is my opinion that the chests which come from China and Assam are made from the wood commonly called here Indian teak. The country round Assam, south of China, abounds in forests of this tree.—W. StephenSon.

[3«9]-BANKAL WOOD.-Bankal wood, of the Philippine Islands, is theiwood of Nauclea Glaberrima, of the Peruvian bark order, or Jlnbiacea ; this wood, of a golden or a greeniBh yellow, is esteemed for Its tenacity and durability, is employed by shipbuilders, coopers, Ac.; it is abundant iu the Philippine Islands. For more particulars on the woods of these islands, see my notes in the Technologist, August, 1864. Some other trees of the Genus Nauclea yield also a good timber:—In Senegal, the Koos, Nnuclea Africana; In Tahiti, the yellow wood of N. rotundrfolia, hard, and excellent for carpentry purposes; in Ceylon, A. Coadunata, Boxb.. tho Bakmee-gahaof tho Cingalese, light aud tough, used for doors, Ac.; N. cadamba, Halamba of the natives, and A", cordi/olia, both used for building purposes; In Java, A', lanceolata; Angriet, Malay, brown, hard timber, very difficult for working, nevertheless employed by wheelwrights ; aud N. purpurea, or Tjangtjaratan, light, with rather loose fine fibres, working easily, but having no special use,—BeritarDin.

[2461.]-INHALATION OF IRON DUST.-Perhaps " A Turner "had better suspend a horshoe magnet over his lathe. The magnet attracts the small particles of steel that fly off, and prevent much mlschier to the workman.—J. M.

[2104]-TAR\ISHED SILVER LEAF.-Perhaps you " clear sized" your Bllver before you covered It with "mastic varnish," in which case it must tarnish. Silver again with fresh silver leaf, and varnish directly with best pale copal or body varnish. Mastic varnish is a spirit of turpentine varnish, aud does sometimes become dead and opaque—The Welsh Shepherd.

[2471.J-SUMMER BEVERAGE.—The following is a good recipe for lemonade: Pour J.oz. of essence of

lemon upon Ijlb. of refined sugar, not broken. Put 3oz. of tartaric acid in 2 gallons of cold water, lee u stand 12 hours or mire, put the sugar which has absorbed the essence of lemon to It, and stir up. When bottled, add a desert spoonful of carbonate of soda iu a quart bottle not quite filled.—Minnehaha.

[24S1.]-GUAN0 INJURIOUS TO HEALTDSciencc Gossip, September, 1866, quotes the following fact from tho Gazette dc Lausanne:—" A peasant cutting wood was wounded by a splinter, and having afterwards worked in guano, this substance entered the wound and occasioned death by poison af ter three days' suffering."—X. Y.

[21«2.] - BENNETT'S CHUCK.-For reoly sec "J. K.M'.'s " letter on another page.—Ed. E. M.-

[54y9.]-APPARENTAN0MALY.-EdwardHabergham has got fogged by mixing troy and avoirdupois weight together. Pennyweights appear in the former only, which has 12oz. to the pound of 5760 grains. It is well worth bearing in mind that thou<*h the troy pound is so much smaller than the avoirdupois pound uf 7 uougr., yet the troy ounce has 480gr. against the 4.17$ thai go to the avoirdupois one, for If you go to a sale and buy plate at per ounce, aa a friend of mine did, and get charged by avoirdupois, you will pay about 11 per cent too much. It must also be remembered that the apothecary's drachm Is aOgr., ond the drachm, as I think it should always be spelt, though wo do not find much distinction made In the dictionaries, is about 27jgr., and Is what we talk about when wo say we put 3dr. of powder Into a charge for a small-bore rifle. As regards the weight of water, we commonly see put In books that a gallon is 101b., also that In a cube-foot there are 6 232 gallons; and should conclude that a cube-foot would weigh 62:i2lb., whereas we are always told it is 624.1b. It would reconcile matters, and be Just as easy to remember, if it were called 62jlb., and would be nearer the mark a good deal.—J. K. P.

[2501.J-INDUCTION OOIL.-T. J. O'Connor's difficulty would appear to be that uo oontact is completed. Ho must not expect an Iron screw and steel spring to work to any sort of satisfaction. The metals would be immediately oxidlscd|and rendered non-conducting, and no doubt tbis is the case now at the point of actual contact of screw and spring.—Sigma.

KOTBS AND QUERIES.

ri*13.1-TOBACCO FUMES-Cau any reader inform mo of the best mode of deodorising a furnished room containing tobacco fumes ?—B. W.

[2504]-UNIFORM TEMPERATURE.—How can I keep the temperature of a room, and a tank of water in it, at exactly SU" r'nhr., both iu winter and summer .' —Quercus.

[2505.]-WEIGHT OF WATER.-What is the weight of a cubic foot of fresh water and sea water, each at 60° Fahr. ?—Quercus.

[250fl,]-CAMPHOKATED COLZA OIL.-Will C. '.Vard kindly state what this is, aud how prepared? I have a real argand lamp, the cotton in which is raised and lowered by a rack and pinion; it gives an excellent light with sperm oil, but this is far too dear, and the common colza oil will not suit, as it crusts so rapidly, the tubes in the lamp being very close, and the cotton fine. Possibly tho camphorated colza oil mentioned by Mr. C. Ward might suit.—S. J. M., Pejge.

[2507] -RECOVERING GOLD.-I see in lost week's English Mxciianic a plan to recover the silver off of plated ware without dissolving either copper, brass, or German silver, '*hicb I consider very useful. Can you or any reader of the Mechanic give the same for recove-ing gold off plated ware, nnd also how to recover the gold afterwards in tho metallic state, as I have some old spoons that have been gilt pretty thick on the metal that 'hey are made of, which looks like copper ?—T. R. D.

[2508 ] - FASTENING STENCIL COLOURS ON PAPER.—Can any brother reader Inform me of any method of fastening steucll colours on paper that will size and varnish. I hsve tried vinegar and alum to fasten the ordinary pigments that are ground for paint, buttboy won't stand the slzo. I have UBed stiff colour ground In oil and well diluted with turpentine, but it is apt to make greasy and unclean work ?— Painter.

[2301).]—PUMPS—Many thanks to " C. S." for his

Frivate answer to my inquiry about the turbioe wheel, see that it will not do. I would like to know what would be the most advisable plan for to send up about 4000 gallons of water in the shortest time ; driving power, 8ft. of a fall, and 50 gallons per minute? In reply to "II. B. M." There has been a ram tried already and found to be insufficient.—Plumber.

[2510.1-PEPPER MOTH—TO MR. CLIFFORD.— I should esteem It a favour if our friend who writes us those iuterestiDg monthly chapters on ourious catlerpillars, or some other brother reader, would favour me with an answer. What colour is the larva of the pepper moth (Amphijdasia betularia), an d what position found In when feeding; also what it feeds on, nnd what localities are;tlie most suitable to it? What lime of the year does It make its appearance ?—Pupa.

[2511.]—BEER.—Would you or some brother reader Inform me of a book treating on the benefit to be derived from the moderate use of intoxicating drinks as beverages?—A. L. E.

[We know of no such work, though the benefits derived from moderate drinking havo been written ou and spoken on again aud again. It is, however, our opinion, grounded ou a long experience and much observation and Inquiry, that the benefits derivable from the habitual use of alcoholic beverages are very small indeed. We do not say this from a teetotal point of view, but as ordinary observers of the habits cf men. We have known hundreds of men, some of Whom were miners and sailors in Cornwall, spinners in Manchester, agriculturists in Devonsbire, aud printers in London, who have abstained for years together from all kinds of intoxicating drinks, and theu we have known hundreds of others similarly

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