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Uxese results (formiDg part of a series which I obtained t>y long and laborious calculations) were not obtained ~tay Mr. Lockyer himself—not even inverted commas.

But I repeat, as respects this passage and three other far more noteworthy instances, I make no charge a t£iiififit Mr. Lockyer, save of having forgotten to duly indicate the source whence ho had derived his inforitmtiou. Had the complete, omission of my name from Jiis book been intentional, the matter would have been •liflerent. As it is, I should not have referred to it at ull "but for the angry and discourteous note he appended to a paragraph in which 1 had paid him a high but riot undeserved compliment.

Tlie factis, that Professor Pritehard and Mr. Loekyt r combined their fo;ves to attack me (apparently for rio other reason than that, like them, I work in the field of popular astronomical literature). If in self-defence I have faced them, and dealt each a blow '* straight from the shoulder," they have themselves only to tkuvnk. I am neither quarrelsome nor thin-skinned; Imt no one shall make unjust and ill-mannered attacks upon mo with impunity. Pacem amo, helium non timeo. Kichd. A. PitIr;Tor..

WINDMILLS.

[-103] Sin,—In reply to "Derf Errac," page 150, lettoi 152,1 should recommend him, before going to work upon models, to procure Smuaton's work on the ** Theory and Construction of both Vertical and Horizontal Windmills." Smeaton was the engineer win* "built the famous lighthouse on the Eddystone rock, near Plymouth.

He should also know that the rustic form of horizontal mill was in u-.e among the Tartar nations before the timoof theCrusadcs. Yoliaui'sphiu for the same object may be frequently seen bet up in the gardens of retired sailors, iu the form or lour full-rigged ships fixed at the extremities of four arms revolving upon a central pivot, a form that has been known ever since vessels at sea were found able to turn a complete circle with the same wind. All these forms are powerless for effectual work, unless constructed of colossal dimensions, and then their speed is so slow that formidable trains of wheels and piuions are required in order to porform any useful work

"Derf Errac" is astounded at tho magnitude of the proportions of my horizontal mill, but the arms are onlv 18ft., whereas in the common vertical they are often oOft. long. It is true that there is an addition of l*2ft. to the radius, for the funnel openings aro indispensable for concon tration of the wind, without which no useful purpose can be obtained; and it may bo observed that there being no movable parts, there is no wear and tear.

If "Derf Errac " would take the trouble to construct a model of my machine at the expense of a few sticks and some sheet zinc, he will find the immense advantage of concentration still greater on the large scale.

A horizontal windmill was to bo scon at the beginning of the present century at the south end of Battersca Bridge, but being constructed on erroneous notions, it was soon done away with. It was in the form of a tower HOft. high., with no provision for concentration, us may be seen iu old views of Battersea Bridge. I was in that mill, however, before it was taken down, and found that it was only driving one pair of stones at a very feeble speed. Henry W. Reveley.

ARTILLERY DISCHARGES AND RAIN.

[204] Sib,—I am not at all surprised that the Editor of the Times thought the letter of "R. P." (page 448) not worth publishing, for had your correspondent been as well informed upon tho subject he writes upon as he professes to be, ho would have known that the question has often been mooted, but no "right men" have ever thought it worth taking it up. By the way. what does " R. P." mean by "right men"? Does he mean Government officials, who might be induced by some "moonsliiny" theory, to squander tho public money in vague experiments? or does he mean private in<lividuals? If the former, taxpayers would raise a very decided and rational objection. If tho latter, I do not think any private individual could be found foolish enough to spend either time or money, for the benefit of a few, in making experiments, the theory of which is pure fiction.

I maintain that rain is not the inevitable result of a concussion of the air, for I have -particularly observed the weather after artillery practice on more than one occasion, and as an instance of great concussion of the air which did not result in a fall of rain, I may mention the explosion of tbe Lotty Sleigh, in the Mersey, a few vears atr0. This explosion wag so terrific that the noise was actually heard at Birmingham, a distance of about 00 miles. But, supposing for the sake of argument, that " R. IVs" theory be correct, I would ask him of what utility would a continuous discharge of artillery, or a gunpowder explosion, be under a cloudless sky y Iu cloudy weather it would be mere labour in rain, or waste of labour, to cause a concussiou of the air for the purpose of forcing rain, inasmuch as a voluntary shower is, in nine cases out of ten, inevitable. Again, allow mo to ask "It. P." how many explosions of "Government powder-mills" or continuous *' discharges of artillery" would oc necessary to cause one shower of rahi over the whole British area?

I am " quite at sea" as to the relevancy "a stone thrown into a pond" has to an explosion of gunpowder, but perhaps there is some deep philosophy in the allusion beyond my poor comprehension. I think the "mythical millions " that a want of rain has already cost might have been saved, and the "calamity " of a continued drought not only mitigated, but completely

averted, if the " agriculturists of England" had exercised their common sense. It is pitiable to rind that they do not give a wider meaning to their own proverb of *' making hay whilst the sun shines ;" if they did so, they would " catch water when it rained," and preserve it in tanks properly protected, which would be sufficient to supply all their wants during the drought.

In conclusion, allow me to ask "It. P." upon what authority does ho assert that "clouds passing over us, unless drawn down by gunpowder, empty themselves into the German Ocean?" I feel inclined to think this is an original idea, and that your correspondent is his own author. Lux.

[205] Sin,—During four years whilst I was at Woolwich, when the sky was very cloudy and overcant, whenever the artillery fired upon the Common rain generally ensued. I am inclined to think that a rapid succession of discharges from field guns would prove more efficacious than a few discharges at intervals from heavy guns.

Oliver Haldane Stokes, Captain (.late) R.E.

UOW COD-LIVER OIL IS MADE, AND HOW IT SHOCLD BE TAKEN.

['206J Sib,—As one of our subscribers has asked some questions about this important oil, I propose, with your permission, to lay before our readers a short account of the oil, and the best manner to administer it.

As its name denotes, cod-liver oil is made from the liver of the common cod-fish, and other species of Gadas frequenting the seas of Northern Europe and America. The folio wing are the most important species of tho oil-yielding fish, in a medical point of view :— GaduM morrhua or the common cod-lUh; Qadus callarias or the dorse; GadttJtmolva, or the ling; Qadu*carbonariutt or the coal-fish ; and the Gad us midan'juit, or the whildng. From this list it will he seen that cod-liver oil is the product of many other species of fish besides tho common cod.

Tho oil may be extracted from the livers by three different methods:—By exposing them to the stm to undergo a process of fermentation ; by boiling them in water for some time ; or by dividing the livery and permitting the oil slowly to drain from them. This method is now employed in the preparation of the best English cod liver oil. The following is the way in which the oil is made at Messrs. Bell & Co.'s establishment:— The livers are collected daily, so that no trace of decomposition may have occurred, carefully examined, in order to remove all traces of blood and impurity, and to separate any inferior livers; they are then sliced and exposed to a temperature not exceeding 180"'Fahr. till all the oil has drained from them. This is filtered; afterwards exposed to a temperature of about 50? Fahr., in order to congeal much of the solid fat (margarine), and again filtered and put into bottles well secured from the action of the air.

Three varieties of cod-liver oil occur in commerce, distinguished by their colour—the pale, prepared in England, or elsewhere; besides which are the light brown and dark oil from Norway. The difference in colour in tho different oils depends upon the circumstances attending their preparation—as the amount of heat employed, the state of freshness or putridity of the livers, the quantity of decomposed matter present in the oil, and the length of exposure to tho atmosphere. Tho following test is given in Dr. Garrod's "Materia Medica," from which also I have obtained some of the facts as to the preparation, ■&<■., of tho oil. When pure cod-liver oil, spread in a thin layer on a plate, has a drop of oil of vitriol added to it, a beautiful lake or crimson colour is produced, rising from the point of contact of tho oil and acid, and rapidly spreading over the surface. This is probably due to the action of the acid on the biliary principles present iu the oil. By this simple test the pure oil is at once detected; for when other oils not of hepatic origin are present, the sulphuric oeid^doesnot give the lake colour, or this becomes immediately mixed with and obscured by a dark brown substance from the charring of the oil. Such is tho case with whale or seal oil, also with olive and other vegetable oils. Some of my readers may wish to know what cod-liver oil is composed of. It contains oleinc, margarine, various biliary principles, also phosphoric and sulphuric acid, with salts of lime, magnesiit, and iron, and a peculiar substance called gaduiu—very insoluble in ordinary menstrua, but soluble in sulphuric acid, and wiping a blood red colour to the solution ; also traces of iodine and bromine; the proportion of iodine is not more than 0*5 per cent.

Cod-liver oil is a remedy which, at the present time, stands in very high estimation; nor does it appear probably that its reputation will be ephemeral. When taken by patients who have become emaciated from any cause, and whose blood is impoverished, it frequently restores the rlet»h, and, from Dr. Theophilus Thompson's statements, it appears also to improve the richness of the blood. Under its influence, patients often increase greatly iu weight, the inscrease exceeding many times the amount of oil consumed during the period. It has been supposed that the iodine and bromine contained in it might produce the beneficial results, but this, idea is not tenable, for tho effects of these latter remedies are very different from that of the oil; it would seem probable that it acts simply as an oil, and that it is superior to other oils on account of its being more readily assimilated. If the statement of Winkler, prove correct—namely, that the oleine differs from ordinary oleine in not yielding glycerine—

this may in part explain its value; but how it acts is still undetermined.

Some people find the oil unpalatable, from the manner in which they take it. Thus, some take it upon ale or porter, others upon milk or water. Can it be wondered at that such patients cannot 14 master" the oil? I have always Found that the oil can ho taken better upon some orange wine, or some mixture containing quinine and sulphuric acid. The acid covers the taste of the oil, and the quinine acts also as a tonic. Some patients cannot even take the oil whin thus mixed with the acid mixture, and for the use of such I recommend the following:—Tako of picked gum Tragacanth \oz., dissolve in 20oz. of boiling water, odd sngar according to taste, now pour into this mucilage lOoz. of the best cod-liver oil, shake well; three drops of ess. lemon*, and the same quantity of ess. almonds should now be added, and if you wish to keep the mixture for some time add '2oz. of brandy. In this compound the oil combiuos with the gum and forms an emulsion of a milky-white colour, which few will know from a well-made custard. The dose, of this mixture is just double the quantity of tho pare oil. The dose of tho pure oil is from 111. drachm to loz., taken at the time of a meal or immediately after food. It is often advantageously administered nt bed time; and my friend, "A Mechanic," will be) able to take his at dinner-time, and so dispense with a pudding.

Patients often find that after they have been taking cod-liver oil for some time they turn from it with disgust. Why is this? I have already remarked that of all oils tho cod liver oil is tho most easily assimilated by the system. But after a time the intestines refuse to absorb it, and that being the case it passes through them, and is found in an unaltered state in the fa?ces; thus, by a wise provision of nature, directly the oil is of no more use, a dislike i-i felt for its employment. If, then, people find that after they havetaken cod-liver oil, say for two weeks, it does not agree with them, they should leave it off for about a week or so, then take it again, and so ou. By these means the full benefits of the oil will he derived. I trust that these remarks may be of some use to your readers.

C.J.H.W.

CARRIAGE WHEELS—THE PHANTOM AND OTHERS.

[2071 StR,—In the controversy on the relative merits of the spider and phantom wheels, which aro but differently proportioned examples of Jones's suspension wheels, modified to render them suitable foi light vehicles—modification which may be taken as representing the most modern forms of the principle of suspending the weight to be carried from the top of tho wheel by rods or chains, instead of supporting it on legs or struts, which is just what wheel-spokes are—in the common way is carried out.

As it is well known that a very much greater weight can be safely supported by an iron or steel rod when that weight is suspended to it than it can safely bear if employed as a column in constant motion, like a wheel spoke, which must not only be incompressible, bnt also sufficiently rigid not to become bent in use, it follows that so long as it is not employed to communicate the driving forces from its nave to its periphery—in other words, so long as it is not required to act Hke a cogged or toothed wheel, or as part of what is termed '* frietional gearing," but as a mere trailing wheel, and its axle is kept nearly horizontal—a wheel to carry with safety a given weight may be constructed on the suspension principle far lighter than in the ordinary manner.

Suspension wheels have tho further advantage of being somewhat cheaper than those with spokes, for rod iron or steel is less costly thau spokes, even when tho latter are formed by automatic tools (ifot to mention costly hand labour), as in the case of artillery and waggon wheels constructed for Her Majesty's military service ; bnt, as ordinarily made, they are very unfit—from their want of rigidity, in the direction that the driving force i*> communicated—to act asdrim'np wheels either for locomotives or velocipedes. A driving wheel requires rigid arms or spokes, just as a cogged wheel does, and the only practical question is how the needful rigidity may best be obtained without needless increase of weight.

The usual method in the ease of locomotive wheels is to construct the spokes of rigid iron, so that they may not sensibly bend when transmitting the driving force. When this plan is carried out in a velocipede it adds considerably to the weight of the driving wheels, which is a serious objection when it is considered the rider has to lift his carriage up-hill, which he must do when ascending inclines. The " PJiautoni" may be sufficiently rigid, especially if of moderatediameter; but, if I rightly understand, it has the same defect as the " Spider," viz., that each pair of suspending rods are attached to its nave in the same plane. Now if the rods be short, as in the case of a 30in. or 4iiin. wheel, they may, if unnecessarily thick, be rigid enough to perform the function of levers, and transmit the driving force from the axle to the periphery of the wheel, without the weight of the latter being made very great, bat it is obvious that if the rods are only strong enough to (safely) suspend the weight of the carriage and its rider, they cannot, when each pair is in the same plane, also be rigid enough to act as levers for transmitting the driving force.

To enable a suspension wheel to become an efficient driving wheel, each pair of rods, instead of being in tho same plane, should be attached to its nave at a distance apart equal to the nave's diameter; that is to say, in nautical language, attached /ore and ajt.

All the suspension wheels I hare seen, until the principle «U applied to our hobbies, alias velocipedes, have been trattiny wheels. All cart, omnibus, cab, and railway carriage wheels—excepting the driving wheels of locomotive engines—come under this category ; and for railway carriages whose axes are nearly horizontal— excepting when the wheels are so stupid as to run off the metals—I think suspension wheels are specially suited. I have a very strong opinion that whon my respected friend Bridges Adams' notions of the advantage of reducing the dead weight to be hauled have come to be appreciated n» they deserve, suspension wheels, with mild steel rods, of a quality resembling steel music wire, will come into use, not only on account of their much smaller weight but also because of the great facility of repairing them. Weight is of comparatively little importance on level railways; for a wheel, even if it were a solid disc of iron supports its own weight, and therefore that weight does not add to the force of traction required to huul it; but when we encounter gradients of one in twenty or more, all the weight of the train has to be lifted to the summit level, and this requires more coal than to make it follow its leader on a horizontal lino.

It will be understood that I do not propote to make the driving wheels of a locomotive engine on the suspension principle. In them weight causes "bite," and so long as the wheel and rail have to be pressed together it can little matter whether comparatively light wheels are pressed to the rail by a load on their axles or by the weight of the wheels themselves. Ou the contrary', the heavier the wheel the greater the "bite," irrespective of the load on its axle ; so if the driving wheels of a locomotive engine were solid costings, like a pair of iron-edge runners (which one of my men called cast-iron grindstones on the same principle that our Mary Ann sayB she " biles" unclean garments in her "iron " copper), it would be attended with the advantages of less wear (from diminished pressure in the axle-brasses) and cheapness of construction, for it costs less to cast a heavy disc than to forge a wrought-iron locomotive wheel.

If yon think a suspension wheel on the principle I suggest worth engraving I shall be happy to send a drawing. The Harmonious Blacksmith.

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wheels 3Gln. ditto; hind axle "in. long, with Sin. cranks at opposite points. The connecting rods are only Jin. diameter. The two front hanging levers and pedals, as well as the centre framing, is of wood. It steers easily with the two handles firmly fixed to the front axle. It needs no brake, as it is under perfect control by the feet. The muscular exertion is not at all fatiguing, as the muscles of the body are as well supported as if sitting in an arm-chair. There is a steel spring across the point-axle which takes off all coucttssion. I can get up any moderate incline with it, and think it would do ten miles in an hour. The distance from axle to axle is 31in.; ditto, between front wheels, 31in. I beg to congratulate y*u on the success of your journal. H. ChildS.

ANSWERS TO QUESTIONS.

[209] Sir,—When last doing this I forgot to state that "W. T.,'* who has had very considerable experience in *' bushing," i.e., lining with cloth tinholes in the butt* of pianoforte hammers, has partly written an article ou this subject, which I expect will let more light in on it than anything I can say, who on such mere practical details can only shine by reflected light, i.e., mere moonshine compared to that of the original laminary. May I request that my fellowenquirers will in future adopt the advice of Di Yeruou to F. Osbaldiston, Esq., and ask all merely practicnl questions at him instead of at me. He has premised to answer all such arrears in one batch, and not only reply to Mr. Moffat, No. 2640, but " correct "— a la tutor—I hope not with a birch rod—Mr. Kemble's odd notions concerning the bushing of pianoforte centres.

I cannot fall to mind where I saw the engraving of the foghorn which ■• E. A.," No. 8780, desires a copy of, or woold have sent it. It is voiced exactly like the reed trumpet pipe of an organ, excepting the proportions of the reed to the pipe, the former being very unusually large in proportion to the length of the "latter, and made stiff enough to bear an enormous pressure of wind.

The Harmonious Blacksmith.

THE 100TH PSALM, ARRANGED FOR FOUR VOICES, BY GEO. COOPER, SEN., CONTRIBUTED BY THE "HARMONIOUS BLACKSMITH" FOR THE ESPECIAL BEHOOF OF THE TONIC SOL-FAISTS.

[210] Sir,—Rarely indeed do I fail to fulfil a promise, but mine to send a familiar tune in this notation, has remained so long unfulfilled that I am not surprised at an occasional gentle reminder. May I hope this will be received as reply to all demands.

In selecting "All people that on earth do dwell"— not even excepting those savage man-murdering races, the French and GermAn, who have not only ceased to cultivate either social or musical harmonious relations with each other, but have also substituted for them that worst of discords, war—for the purpose of illustrating my old friend's system of musical notation, I have been induced to do so because all people know ** All people," and because as almost

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all people possess 11 All people" in our ordinary com-!. plex notation, they will therefore be^ able to compare that with this, and, if wise euough, to admire its beautiful simplicity. If not all people, many people at the least among my fellow-readers, will also be able to compare this with the popular and much vaunted Tonic Sol-Fa system, which, to my crass ignorance, does not appear equally with this to possess the beauty of simplicity, however much of that Bame article some of the advocates of the Tonic Sol-Fa system may themselves have manifested.

As regards absolute originality, I fear I cannot justly claim for my old friend much more tban most other inventors. have exhibited. His notation, when | examined by the light of the experience of those who are accustomed to music by handle, is resolved into a copy of the pins and staples of the barrel of that "horgun" made by the said handle to discourse the "sweet music" which drives Babbage to distraction, and compels quiet folk to pay for the privilege of silence, which we then—after this infiicton—do indeed recognize, in the words of the Chelsea philosopher, to be golden. This copy of these staples and pins, written on two staves of five line-, each, is neither more nor less than the notation befoicAASS STAFF TREBLE STAFP the reader.

The idea of writing the note3 or signs of the sounds uttered when the black keys are depressed on the lines, and those nttered when the white keys are struck in the spans between the lines, for tbe purpose of avoiding the necessity of nsing signs for sharps, flats, and nutnrals in music, written for keyed instruments, with fixed intervals, is no novelty. If I am not much mistaken, it was done in the notation published by a reverend gentleman, whose name I forget—I think the same person who also anticipated Hawkins in the construction of apparatus which recorded musical performance on keyed instruments. About forty-five years ago I saw this notation engraved in an early vol. of the Phil. Tram., date about 1080.

Anything simpler or more easily impressed on the mind of the intelligent tyro tban that all the notes are of the same form, and the fact that the length of any one note in this system expresses its temporal value, it would be difficult to imagine ; but this peculiarity, how

ever valuable, cannot be properly tinned u iir.^ —it is rather the observation* of an exxste&l hw. . the lengths of the staples in tbe organ bmvi dmine the time each of the pallet* is kept ou K consequently the durations of the &onnds ■■■"'. so a mere copy of these staples on paper sVn> i relative leagths, and must have indicated ft* ts each note to so appreciative a mind as H.

To those of my fellow readers who can i^pbeautiful hannouy I especially recommendtHjis" ment or setting of the "Old Hundredth" few voices, in which the bass voice sings tts sa. scale iu contrary motion. For the manuscript 11_ gem, which is by Geo. Cooper, sea., late «aa St. Paul's Cathedral and St. SepnlchrV* Cacti 11 indebted to the kindness of my friend and hfcv-%* spondent " \V. T.;" and I trust all my mttatU readers, not excepting Dr. Ussher, from wka**. heard but very little of late, to oar sarrv*. C, pleased with it.

The Harmonious Bz_tajc:

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FRUITLESS LETTERS.

[-211] Sib,—Would you have the kinA*. — me through the Mechanic, or by letter, mis-. can recommend that makes the best Kqu adapted for dress making and general » a you will greatly oblige me?

Kearsley, Ang. 2nd, 1870.

[We frequently receive letters like theafc** we never on principle give the inf ormauos * We think that a publication devoted to iec cation, or, in fact, any other kind of *--fi~.-.i.-.never recommend the goods of any pmrfr-"*^ facturer. Weak journals may, and fftsraanir ■ i things "for a consideration;" bat «tran* . rshould be, like Cesar's wife, ** above Mpea' ■ all events it is useless for any oat •-,. — a* ■ E. letters as the one above.—Ed. R. M

MAMMOTH.

[213] Sir,—Only two skeletons of t^su&BOU i>?jr-phasprintigenius, are existing, I thiajL:r ;ra*«Efr-<E-' mammothofthe Lena,at#t. Petersterz Job Ou mammeii of Lierre, at the M uteum of Natuni£i<*jrr at Broad-another specimen was discover** a 1366, aea* Tomsk in Siberia, and a commiaaa La baa -war1 by the Academy for the purpose of A Raniu St Petersburg. I saw the magnificent uMriaa <& amammoth of Brussels some monthi tsp, aai t V» particulars of its discovery may prerc

In the month of May, lt*60, when cot near Lierre (province of Antwerp*, the buried in the sands the skeleton of i this skeleton was lying on the right column very much bent; the head was «■ was also a tusk of enormous dimension* ribs of the left side were missing, were broken, or rather discomposed. Mr. * military physician, recognized that it wa? & **• of a mammoth. He had all the boawoj^*£ they had lost their solidity; the head, ttfa* *■** weight, split and separated into Qusmw ^&some other bones also suffered from av cva^sea^tA in the transport.

Theso ancient remains, deposited fete -assess • Brussels, deteriorated every year nntil&*«p»towf-~ Dr. Dnpont—so well known by his imrrrS'^na-" * Belgian grottoes—undertook to restore t^» ftt « aided in this difficult task by Mr. Dapaan. <at d auxiliaries of the museum, who gave proofs wzar'^ circumstances of great skill and p^rsev-enum. lfti.* months of laborious exertions the mam mot* ol Lr was entirely restored in the action of waJlanc

The height at the nape is 3m. 60; the 2tvi£fc*. - Indian elephant, of which an ad tilt akedctva v- existing at the Museum of Brussels, is onlv ^m ^ head weighs 250 kilogrammes, and the ta*k Icjj2m. 00, following the curve.

The restoration presented great diflfioTUD*- i well as the restoration of the missing t*.ic*s i skull had been reduced into more than 200 fra£zi-.\ nearly a third part of the skeleton was waab^ 4 had to be carved in wood; the humerus, for- -whvi I museum did not possess all the requisites, cooid cc restored by the study of another hamerns bwlos^j the University of Ghent; one of the tnaks is arsi. one tibia and one rib do not belong to the same ar 1 but to an individual of the same species, bei^h- i age.

The manner of patting together the mamn. Lierre deserves special attention. In some xoo*4 galleries the bones are perforated, and are ati^hri gather with iron wire, and so rendered motionlomammoth of Brussels has not a single bone pcrfem By means of some adjusting screws every- bone c*u taken away and examined. The whole of this enorxs skeleton can be taken to pieces in 20 minutes aic up again in less than one hour.

For other particulars on mammoths, espevI«JT i that of the Lena, see Intellectual Observer* Ft t - j 1867, page 70. Ban

OUR SIZE AND PRICE.

[213J Sib, — When about to incorporate Mechanic yon invited suggestions. I, b* ;r.. majesty's (self-appointed, if not self-named) sago -: general, then did mine office. One of the said B»u tions was to extend the journal to eight page* ap and charge Ud. for it. Considering you have to rv

fiood many communications, and have undertaken to ...port the doings of the scientific sociehes-not to arution reviews and extracts from new books—I cannot ielp thinking vou could weU occupy more space. It ■oca against the conscience to buy for 2d. what is Loneetly worth 8d.; but, commercially, it might be advantageous to enlarge both number of pages and l»e price at once. Your present capacity is hardly uirae enough for the journals and their contributors which you have absorbed, uot to mention one or two ithers which may be absorbed. So I cannot help thiukim» that the sooner vou relieve our Tendeb consciences from the reproach of receiving more than an equivalent for ©or twopences the better.

The Harmonious Blacksmith.

I Though the "Harmonious Blacksmith" is not the only one who has made a similar suggestion, we think it right to say that we have no idea whatever of increasing the price of the English Mechanic. As to its size we do uot know what it may grow to: much, however, wiU depend on the activity of our constituency, of readers and subscribers. It is possible to permanently increase it eight pages without any increase of price. Let us have three subscribers ■where we have now got two, and it shall be done.—. Eo. E. M.]

CHEMICAL FLORICULTURE. [•214] Sir,—The three primary colours, red, blue, ami yellow, are not to be found pure in any species of flower. We have red and blue in fuchsia, but no yellow; yellow and red in the rose, but no blue; blue and yellow in the heartsease, but no rod, and so on. 1 mean, be it understood, decided primary colours, anil not secondary. As this seems to bo a law of nature that sets the'art of man at defiance, we may expect blue dahlias, yellow geraniums, and scarlet pansies when the circle is squared, but not till then.

Dan Rosen.

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THE SYMBOL », CONIC SECTIONS, ETC.

[216] Sir,—" Gimel " should have told ns he wrote ** to argue," and not for information. "He knows all about the matter," he now says. Apparently, however, he does not know that a ratio is bat an abstract quantity. Todhnnter is quite right, of course. "Gimei" might as well say that the symbol 8 does not iuvariably represent the number three, because it also represents the number of angles in a triangle.

I should regard "the section produced by a plane passing through the vertex of a cone" as either two intersecting right lines, or one right line, or a point (according to tbe position of the plane), not as a hyperbola. One may, if one so chooses, speak of a circle as an ellipse, whose eccentricity is zero; of two intersecting lines as a hyperbola, whose axis is zero; of a right line (or rather two coincident right lines) as a parabola, whose Intus rectum is zero, and so on: but 1 do not see the sense of it myself. Richard A. Phoctor.

P.S.'—Todhnnter and the Symbol w.—Todhnnter is right, of course.

MOTIVE POWER FOR VELOCIPEDE.

[217] Sir,—I cordially join with Thos. Stanhope in hoping that some of yonr talented correspondents will be able to design a useful, safe, and moderately priced steam velocipede. I have read with the greatest attention and interest every new description of bicycle and velocipede which has appeared in your journal, each ono professing to be the easiest and best ever invented ; still I am as much at a loss as ever as to a selection of the most practically useful machine for a man who is too old to care either for the excitement of n little dangor, or for too much physical labour, but who would gladly make use of some means of locomot ion for his daily journey to business, rather swifter than his own feet, and rather less costly than a quadruped. Is it too much to look forward to the time when every road will be a tramway, and when steam carriages will run on them without any danger or inconvenience? and can we not " educate" the public in this direction by a "pioneer " steam velocipede? II. M.

the second coat, " intonaco," i* floated all over the wall, about 8-8in. thick, firmly pressed down with the trowel only; it is then left to dry. When perfectly dry the face of this last coat is rubbed down with sandstone to remove the thin skin which has formed on the surface; this thin skin removed will leave the wall quite porous, and now the painting may begin, by first saturating with soft water as much of the surface as can be painted in a day; it is also well to keep the edges wet for the next day, when the same is repeated until the whole wall is finished.

In this method the joins are avoided. But painting in fresco is now superseded by stereochromic painting, also sometimes called water-glass painting, a method which gives the artist perfect control and freedom over his material. One may work a painting over and over again until the desired effect is produced. An artist who is used to fresco, to body colour, or distemper painting, can master the details at once; besides the work is more durable than fresco; the two large pictures in the House of Lords are executed in water-glass medium.

The method is this: After the wall is covered with the second coat of mortar—one lime and two fine washed sand—the wall is left to dry perfectly. The colours are ground in pure water only, and applied with no other vehicle than water; the same colours are used as in fresco, no vegetable colour is admissible; when painting, the surface is first wetted to displace the air from the pores, the colours are worked into each other; when all is finished, the colours are only on the surface and will not bear to be touched; the whole painting is now fixed with water-glass solution in a diluted state the solution is applied with a syringe for the first time after it is done with the brnsh.

The above is only an outline of the method, but if required, and with permission of our kind Editor, a detailed account will follow. The Welsh Shepherd.

WALL DECORATION.—FRESCO AND STEREOCHROMY.

[218] Sir,—Your esteemed correspondent" Sabbas" has given a very good and short description of fresco painting; however, there is a more simple method not generally known. It is thin: When the rough cast is dry,

CURIOUS SENTENCE.

[219] Sir,—I am attracted to this topic (p. 423, letter iJ2; and p. 4t>9, letter 164), by my having a different reading. The central letter, as I always knew the passage, was not R, butN : Sator arepo tenet opera rotas. Meaning, (tator) the sower (arepo) of mischief (tenet) keeps (opera) his works (rota*) on wheels, or a-going. It was, in old times, the schoolboy tradition amomg my comrades that Arepo signified of'mischief; the same word occurs in the {venerable I) nursery rhyme:

One-ery, two-cry, six-ery, seven,

Arepo, crackabo,ten and eleven;

Pin, pan, musky-dan,

Twiddledum, twaddledum, twenty-one.

Arepo is probably a bogie word; it is of Syriac cut, and of eastern origin. The Mohammedans have a grea deal about Araf, the partition between hell and paradise, see the Koran, heading of chapter vii.; Araf being much the same as Erebus ; thus arepo might possibly mean deeds of darkness or mischief. We must not be too severe on the classical Latiuity of the like; the passage affects to be an iambic trimeter verse, but it is merely a monkish amusement. The best known is: Roma tibi subito motibus ibit amor, i.e., Home, on thee suddenly with its emotions shall come love. This is by Sidonius Apollinaris, a Christian writer, A.d. 4H'J. Amedireval toy of the kind was : SacrKin pingue dnbonou macrum saorificabo, which is an hexameter, meaning ; I will give a fat victim, I will not offer a lean sacrifice—alluding to Abel. But the same read backwards by words is Cain's offering: I will sacrifice the lean, I will not give a fat victim; and this is a peutumotcr. Such a quaint conceit was called the Palindrome, or Sotadic verse. The latest play «f the sort I know is tbat Mr. P. G. Hamertou writes capital letters from abroad to the Globe newspaper, and signs his name G. P. Notremah. Gimel.

THE INDUCTORIUM.

[220J Sir,—I will, with yonr permission, make a few critical remarks on this subject, also with reference to the ingenious method of construction given by your correspondent "Inductorium." First, the tension of the electricity or length of spark depends on the number of windings of the secondary wires {«<r,teria paribus). In my opinion, if tension is required, the induction coil should be made longer, keeping the diameter constant. By this method, the number of windings and length of spark would he proportional to the length of wires. To obviate the inconveniences of spools of great length, large coils might be divided into sections, and combined in a compact form. As an instance of low tension, considering the length of wires used (viz., 150 miles), I may cite the coil at the Polytechnic Institution, which with full battery power gives only 25in. sparks. A spark 4in. in length, has been obtained|from three miles of secondary wire; therefore, if the diameter of such a coil were kept constant, and 150 miles of wire used, sparks of l(5ft. in length would he obtained. The following, I think, proves the correctness of the above reasoning. If two coils giving 4in. sparks be combined, aud the current of the battery be kept constant, the combination will give 8iu. sparks. If any of your readers detect a flaw in tho above reasoning, I should be glad to have it pointed out, and also to have their opinion (perhaps I may include "Sigma ") on the subject.

May I ask "Inductorium," whose method of construction I like, if he has tried the effect of 5 or 6 cells on his coil? which, I havo no doubt, would give interesting results a- to length of spark; also, did he succeed in winding the wire in regular layers in so confined a space as £iu. between the discs.

S. T. Preston.

THE MICROSCOPIC INVESTIGATION OF MALARIA.

[221] Sir,—I need scarcely say that I have been very much interested in the articles on zymotics which have recently appeared in the Enolish Mechanic, and, as a further contribution on the same subject, I send an account of a discussion at a recent meeting of the Polytechnic Club of the American Institute.

Dr. Vanderweyde introduced the subjeot by showing and explaining the device, as applied to his own microscope, for conducting the examination. Firstly, the liquid was placed in a cell, not such as is ordinarily used in microscopic investigations, but set in a perpendicular position, so that the light may be passed through it in a horizontal direction; the light from the cell is refracted and reflected by means of a prism up the tube of the microscope, and then, by another refraction and reflection, direct through the eye-piece in a horizontal line to the eye. This is very convenient, and saves many annoyances of former methods. Formerly, doctors had little faith in the revelations of the "microscope, and scouted the idea that some diseases were originated by onimalcula—as tho itch and some others.

The researches of Hallier, the great microscopist of Jena, were referred to, and his conclusions with regard to the germs found in the bile of cattle dying of tho Texan cattle disease stated at some length. This Texan cattle distemper answers to the yellow fever in the human system. In the bile taken from these cattle were found germs which not only lived, but grew and increased after the manner of those in yeast. The course of growth in tho yeast plant was then traced, and the resemblance of the other germs pointed out. In regard to those found in the bile, it was stated, and illustrated by line drawings, that their development was very largely influenced by the circumstances in which they were* placed, one form being found when the growth was in carbonaceous substances, and another very different one when in substances containing nitrogen. Another interesting fact was then stated, showing a very close resemblance between the highest developed form of these plants or germs and those found in syphilitic diseases. Further developments resulting from close study of these germs may throw light upon the development theory, as well as the different relations of animals. All animals, during their development, go through the forms of all classes of animals below them—the impression of the parent alone deciding how far this development shall proceed.

The cell that causes the fever and ague has certain necessities of growth, as stillness of air and certain conditions of soil. This cell, or germ, when taken up with the breath, produces the fever. It does not rise any great distance from the ground, aud hence the greater danger of sitting than standing in places where it abounds. The state of the body has much to do with the effect of the germ npon the system. When, after a full meal and in good health, exposure takes place, the danger is much less than when the stomach is empty and the system tired and exhausted. It will probably be proved that all contagious diseases have a common origin.

The use of the spectroscope has done much for science in the analysis of liquids. The two absorption lines of blood, in spectrum analysis, give us the means of distinguishing blood from any other Bubstance, aud showing the presence of any foreign body in the same, as they are never confounded with any others; no two bodies ever producing the same spectrum. In typhus fever the blood discs appear broken up, sometimes flattened and a disc half gone, as though cut in two. We find some poisons useful in disease, and their action may be attributed to their destroying these cells, or their arresting action, as, for instance, carbolic acid in small-pox, where, properly administered both externally and internally, it completely breaks up the disease. The effects of arsenic eating are possibly due to the destruction of organic growths in the system, rather than its arresting waste.

For small-pox Mr. Nash considered warmth, catmint tea, and Saratoga water about the best things; and Mr. Edwards said that one of the great errors of society is that people think that two sets of facts cannot be true at tbe same time, when both of them are true ; for example, we are prone to think that either the chemical, the electrical, or the germ theory of disease is the true one, and the others false, yet they may all be correct. In the fearful epidemics of 1853, he found that at first the strong and healthy were attacked, and those that had been sick, or were just recovering, were the ones that escaped. As the disease extended, all were attacked, and finally the negroes, who had always braved malaria, both in Africa and in the South, fell victims to it. Those who recovered always had been under such treatment as would keep them from getting out of a perspiration; and it was the old nurses and negresses that understood this treatment, and were successful, while the faculty failed.

In the course of the discussion npon the several theories of disease, Mr. Root enunciated his theory of the circulation of the blood and the power of the muscles, which was, briefly, that they acted through the pressure of the blood within them dilating, and Bo shortening them. Dr. Vanderweyde considered that this was disproved by several well-known facts, as the elasticity of the arteries, which, by their expansion and contraction with the beating of the heart, prevented the transmission of power in this way; also the fact that the blood was only transmitted through the walls of the capillaries by endymosis, and not by pressure.

I enclose the account as it has reached me, believing that it will be interesting to our readers in general, and those interested in microscopical examinations in particular. J. T. W.

GAS.

[221] Hii:,—I had no intention of being discourteous to "C. D. C," bnt when any one attacks other people, even though they are united in the form of a " Company"—which is too commonly regarded an a legitimate object of plunder and abused—he mibt expect to get attacked in return : and when any one picks up a foolish and most unfounded charge, and supports it by instances equally unfounded, I, for one, scarcely think it is discourtesy to mm his readers that his knowledge of the subject is too scant to justify them in accepting; his statements, for he invites* this Insetting forth these unsound remarks. For myself, I have not the least personal interest in the matter, 'as "C. D. C." supposes, but I do know what is the truth; and I do know, from years of acquaintance with gas engineers and gas directors, that as full a sense of right and as thorough a desire to do justice to their customers pervades that class as is to bo found in any commercial body or individual; and having watched many of the squabbles got up by interested parties. I know that the cry against the companies is pure claptrap.

As to the manufacturing part of the question, I spent three years, not long ago, in one of the largest Loudon works, with the intention of taking charge of a works; therefore, I am fully able to assure your readers that the notions set forth by "C. D. C." (taken up as they are from people who know remarkably little of the matter, though making much noise) are entirely erroneous. He says (p. 4481, I am bound to

Srove this assertion, and I proceed to meet his esire. The point at issue is tho alleged removal of illuminating hydrocarbons from the gas, beeanse tho companies "find it expedient"—a phrase whica certainly implies that they do so for reasons not covered by the necessities of manufactories.

Now it is not even true that the illuminating power is reduced thereby, for the simple fact is, that the gas, as it leaves the retorts, is totally unfit for combustion as it light-giving agent. It burns with a lurid, smokv flame, and is heavily charged with sulphur and ammonia, both of which the companies are bound bv law, under heavy penalties, to remove. There is no known process for removing these which does not also remove some of the light-giving materials; thorefore, any reduction of the real illuminating power belonging to the gas, after the tar and condensable vapours are allowed to condense (which they must do, or they would choke all the pipes) is imposed on the companies by law to their great loss, for a little common sense will tell any one that it is their interest to koep in the gas all the power possible.

Following down "C. D. C.'s" letter, I do not class Letheby, Franklaud, and the others named as "gas quacks;" nor do they join iu the senseless gabble the real qnacks utter. They watch and endeavour to keep down those irregularities of manufacture dne to the inferiority of materials and carelessness of men met with in all manufactures, and which the gas managers themselves are as desirous as any one to d minish.

Next, as to the dividends, I must point out how "C. D. C." betrays his real miucquaiutauc with the subject and the source of his supposed facts. The companies arc limited to dividends varying from 7 to 10 per cent. Will any one say tins is too much for a trading profit when any day some new improvement might even supersede gas and destroy the capital invested? Remembering also that for very many years the companies scarcely had any dividend at all till improved manufacture—notably the use of clay retorts, and common-sense business arrangement's limiting ruiuous competition—were adopted. But "C. D. C." says, and "the bonus in addition, to avoid the letter of the law "—again an imputation of dishonesty. Now the simple fact is, no company can declare a bonus, and any ono can stop their dividend by showing to a court of law that it is in excess; bnt the law permits them if iu any years they do not make their full dividend in any subsequent year within six to make up that deficiency, and some of the companies have been able to do this, not as a bonus to evade the law, but openly and legally as arrears given them by the fair.

As to carlmretting, I have not the slightest intention of disputing about a matter which scores of patentees have tried at. By all means lot any one try it who likes—as I have, and many others. The simple fact remains, as pointed out by another coutribntor, that after a great flourish of trumpets, and many statistics showing the great profit of the process as used in the city lamps, it u-at abandoned; and the general public steadily declines to patron.ze the many patented plans, and giving my opinion simply as my opinion, I consider it does so very wisely.

I find I have omitted one argument, which, as it i.-. based on truth, must not pass. It is quite true that jig to the mode of working a larger quantity may be obtained from the coals but of inferior quality. This is just one of the questions of manufacture aiid cost—the best way to obtain a gas of the power required by law. If the heat is very high or prolonged, more, but poorer, gas is obtained; and to compensate for this a certain proportion of rich and costly cannel coal must be used. Whut has this to do with the public, or how are they wronged? The company is bound to give them 1'2-candle gas, making it how it. plcazet.. As a fact, tho companies do supply 18 and 14-candle gas, as Messrs. Lethobv and Franklaud show by their reports; and this is tiio way the " public suffer." Siujia.

EXTEAOTS EBOM OOBBESPONDENCE.

Filters filled with black oxide of iron are said to be very effectual iu removing organic matter from uupure water.

BRASS INSTRUMENTS.—J. Samuel says-—"In almost every public work in tho United Kingdom there is a brass band, and there are generally some members who are mechanic-, and most of thorn take in tho EXOT.ISH Mechanic. Now, I think it would be a great boon to them,as well as me, if some well-learned brother reader would write a treatise on all the different kind, of brass instruments and best makers; something similar to what Mr. Hermann Smith is writing about the harmonium."

GAS BY A NEW PROCESS (p. 474.1.185).-" Gimel" says:—"Let me add my earnest trust that this maybe described in a practical way, so that it may be tried. To say nothing of gas light, I can tostify that ono of the most delightful comforts is the gas fire, which you can have blazing, or low, or out, at pleasure; but il is very expensive."

SETTING OF VALVES.-" Paul Pry" says:-"Although the editor has not formally given Mr. Baskerville leave to contribute a scries of papers on the setting of valves, I hope he (Mr. Baskerville) will do so, nevertheless. Such a contribution, especially from the pen of Mr. BaskerviUe, would greatly enhance the value of the Exombh Mechanic to a very large section of its readers. In the mean time, I should be very glad to see a letter on the subject of the expansion valve as an auxiliary to the slide valve, explaining its action, and the method of setting it."

IA note offering space was appended by tho editor to Mr. Baskerville's last letter, but, was omitted in mistake by the printer. Mr. Baskerville lias since been written to, and he will in all probability contribute tho offered papers.—Ed. E. M.]

SPEED OF CIRCULAR SAWS.-A correspondent of tho Scientific Amrriran says:— "It is laid down in mechanics that the speed of a circular saw should be. about two miles per minute—that is, the periphery of the saw shonld run 9,000, or a little over that number of feet per minute. Having had much experience in tho building and the running of saw mills. I have found that a greater speed could be used with safety, of which I will give an example, a mill that I finished and put in operation about eight months ago. I was iu nowise trammelled, and everything was left to my direction, which gave me an opportunity of testing a very high speed, together with a heavy feed on a large saw. The size of the building was Sift, y 100ft.. and two stories high. Size of engine. 15ft. x 30ft. x 82ft., with 83 revolutions per minute. Throe cylinder boilers, 861n. diameter - 30ft. long. Flywheel, 20in. face s 12ft. diameter: weight,8.00111b. From the flywheel, with a20in. belt, is driven a 4iu. counter shaft."with a 4ft. pulley. A (Uft. pulley on counter shaft, with a 16in. belt to a 2ft. pulley on saw mandrel, drives the saw, which is (Win. diameter, running 800 revolutions per minute— 14.lXH.irt. per minute—which is about 5.000ft. per minute oyer the standard. With this very high speed the saw cuts Sin. to the revolution, making a Sin. feed, and in one day of twelve hours, 97 logs, producing over 84,000ft.. were cut."

PREVENTING THE CLOGGING OF BOLTING CLOTHS.—" An Old Miller," writing from one of the agricultural states of America, says :—" A good method of preventing the clogging of bolting cloths consists In thoroughly cleaning them, inside and nut, as well as the l«lting chest, and then passing the flame of burning alcohol rapidly under the whole cloth. Extreme care should be taken to avoid damping the cloth."

THE RIGI RAILWAY.—A correspondent of the Engineer, writing from Fitznau, thus describes this novelty in railways:—"Immediately after leaving tho station-yard the ascent is commenced, and in about 100 or 150 yards tho inclino of 1 in 4 begins, and will, I believe, terminate only at tho summit. Tho rails, which are very light, aro laid down to what appears the ordinary gauge; in the middle is a wrought-iron rack rail of about 4in. or 5in. pitch: the rails are laid on transverse sleepers, and outside the rails, longitudinal beams are bolted to tho sleepers. The locomotive, " Stadt Luzern" by name, has (when on the incline of 1 In 4) a vertical boiler, the cylinders are lljin. diameter, aud 16in. stroke; they are outside, and are parallel to the rails. Tho valve motion is of the straight link kind, the exceutrics being outside the crank pin. As is very often seen on the Continent, tho machine Is supported on four wheels: their diameter is, I should think, Hbout 2ft. 4in.; they are loose on their axles, the rack wheels are keyed on iii the middle, and one axle is driven by the engine bv spur gearing, the engine making three' revolutions to'one of the rack-wheels; the axle which is not worked by the engine has two friction wheels keyed on it for the brakes to press on, and the brake on the only truck I saw was of the same sort." The writer saw a truck containing about 41 tons "pushed "up the incline at the rate of four or five miles an hour.

EYE-LOTIONS.—A correspondent of the lancet calls Attention to tho dangerous practice of would-be philanthropists giving away eye-water to all applicants without reference to the real nature of the particular disease. He thinks, however, where it is confined to tho sulphate of zinc lotion little harm is done. "Tho old family recipe for eve-water, if inefficient, is generally very inoffensive : it is strong of the water: and if it does no good it does no harm to anyone, and produce* little visible effect. It contains neither lead nor belladonna. In ninety-nine cases out of a hundred it, is a very dilute solution of sulphate of zinc (white vitriol, so called). Water, alone, for the eyes is an excellent sanatory appliance, as frequently, perhaps, as it is for generarpurposes of health. But as simple conjunctivitis or catarrhal ophthalmia is the most frequent of eye complaints, a little snlphate of zinc is thrown in on speculation. It sometimes does good, it is very cheap, and it manifests its presence even in so great a quantity of water. We generally use too much water iu our collyria. It was a valuable bint to me some time ago, when n distinguished foreigner observed that our strongest (he was speaking of sulphate of zinc—two grains to the ounce of water) was only the strength of their weakest lotion. But, if one did not know when to prescribe or to omit sulphate of zinc, or sulphate of atropine, or othor common lotions, one could only be safe by great dilution, and aide perhaps by combinations of different remedies."

EEPLTES TO QUEEIE3.

*♦* Is their answers, Correspondents aw rttpor ■ requested to mention in each instance tat uu, number of the qnory asked.

[So87.] — DUSTING BRASS MOULD8.-I la?-. mit the following :—For light wort face vwV' with the following: 3 parts new sand, and 1 pi,. mix it up as you would facing *and and tact K- . with pea-meal. For heavy castings nut Zfa.-", sand, 1 part old, and 1 part dried low. •.' your pattern with, and face your nioald vri , meal. For dry-sand work use S' parts drr I Ji.; , new sninl; and for facing your dry-sand meekly 'jwith, use lime; mix it in water the same *v t . would black-wash. If " Ironfounder" win ti-, . Instructions, he will find that "X. L..," whoui.-^,, * query, is quite wrong. If " N. L..," has bcena**! -" casting, he must know that coal du»t Is note.»~. brass work. In the first place, lira* U ltj, searching nature that it would eat its way ton, casting would be vl.it we call struck afljj- fc if he used black-wash for his cores andd*-.* brass would fetch it all off and leave it ta a-1,. castings, as black-wash cannot withstand**., brass on its surface. Lime is the onlrafja-rj withstand the action of brass; and la*tly,dMfa or blacking are used for brass work, it DUa> look a nasty black colour, almost the &aa -W. J. W.

[275H.1-LAMENESS IN HORSES—H«r „.lameness in horses I take to be no new mru, during 1868-91 obtained from feotne exten«ivt e:~s that were making a few miles cast of Louio... other things, a quantity of horse shoes 5.*vsolid aud heavy, similar to the one figured in n , cnAKie of July 29 (which from the depth ti>s found at must have lain there several hundn-1-r which if usod for lameness, then the one figure*.-., bo an invention, only a revival. I have aboutt»r..i of early horse-shoes, all very different from tW in use; also some old bits and spore. To any ra* tercstcd in these things I shall have much "pieus in showing them,—A Cieiosiit Cotizcroa.

(2756.)-LAMF.N'ESS IN HORSES.-"Country Trt . in reply to J. C. Dutfryn, advise, bleeding in Ibe attiw stages of Laminitit (fever ia Ike feel 1. Intbeinij.nl' of cases the disease consists ol congestion of tbe emir? venous circulation of the toot, and it may remain in thai state for days without taking <<d infiiuuiiation. 3fv treatment is to remove tbe (.rdin&rv shoes, and immediately apply tho bpecial Omi, not' seated, or beviiled, but bearing the whole width on Vb* stle u on the win. unless tho sole happens from being pared to oettm. Give aldose of from :i to G dram* mot otmc« as *inu-l according to sizeof animal, which must "be eompeBedt' take exercise on soft or wet ground If available. *v-i times daily. Should the case be a very acute oat 1-4 water may bo applied during the intervals nl <ierc» and also ten drops of Fleming's tincture of scoafc^ be given every hour until the animal is relieved. "■ aloes may lie repeated in about three days, if asr~or any lameness remains. The majority ef * • arc relieved in two or three days. I neverbka--stage of the disease.—T. D. Broad.

[3766.1 — TO CLEAN, AND FILL IB t~S BAROMETERS.— Buv a glass tunc chwas** S4in. long, small or largo bore as, reqnjaW? with a fine rod with rag or tho small l*m«*^ pipes (tobacco, to he had at any cigar shop. ra*S'-' mercury at any wholesale druggist's, pric« *k«i** crown per pound. Makea funnel of clean wjfcacvs*and pour tho mercury through repcatetTskte^ -' or vessel, until quite clean; tkouiusei-t'aclea=ts»papcr with a line hole into the tube, puv »'£ quarter of an inch of the top; take a chun to ■■''■ and stop up with the finger, reverse and topE" the air bubble up an.l down till clear of sp«>- .J L then fill up. Buy a boxwood cistern (orl-evt"^yourself). and fit it on the tube before with nine und if too loose, nnscrew the end with tho shecp-i^ » and till np, theu screw on, and the tithe is made > looking at the cistern of any mercuriiU baromctfi idea is soon got hold of. Adjust by a youd rule, Im good barometer of a friend or public instituu'ett. ''■ work may be made to fancy. A Bcrew at the bott-'E^ enable the mercury to rise to the top, Mo as to be cmabout without risk. My advice to amateurs uk *• make many, as tho fumes of mercury «re very ui1 a* —far better purchase.—GnonoE Mackak.

(3815.}—EMERY WHEELS.—The expressed oil-!. seed, like several other vegetable oils, but in a jrr. ■ ■ degree, is capable by exposure of absorbing a !■'amount of oxygen. It is this property of linww! which renders it so valuable for mixing with pipnw:' as it is this gradual absorption of oxygen -which"k-t <■' the oil, aud produces the pheniomenou of drying ii * paint. For this purpose linseed oil is put through :t process of boiling with litherage aud oxide> of lead, :rwhich it absorbs so much oxygen as to promote it--If ing properties. In this condition it is styled " bnuVJ!" seed oil." This peculiar property of Unseed oil rcnJt it very valuable in certain arts, as bycontinningtheen tion by prolonged exposureto the fttniosphere it assaias tho appearance and character of India rubber, bta very tenacious and durable, which any one can pem-.i in tho durable qualities of ordinary wax-cloth. The1 emery wheels are formed of clean emery componv., with just a sufficient amount of boiled linseed oil. t'-> mixture being agitated for a sufficient period under f' posnre to a considerable temperature and a tree nfi-i". of atmospheric air, or some still more powerful ovi.ii. ing agent, can be made to assume the necessary de>^ of tenacity, and whilst warm, being exposed to h>d-*s lie pressure iu a suitable mould, and subsequent Vfrji" in a stove, the emery wheel is complete.—Mateix.

[3851.]—HARNESS.—"Saddler's" reply would but been valuablo some years back. I will eive in advice and experience. If you use a " comp«>siti.n your harness will require constant applications of oil an dye, and scraping—tbe former to keep it supple nr. black, the latter to take away the cracky app^arai.0 I find Clarke's harness blacking far preferable to an. r. ccipt I over tried, and I am told it contains tho right pr. portions of oil, dye, and polish.—Not A Saddle*.

rS9491—GUYANA OR GUIANA.—These are three -oionie's, belonging to the British, Dutch, and French, >f this nnme. Thev are situated between longitude ilJ 30: nnd 61" west, and latitudes 1-to fl" 38- nurth. ►"eneznela lies between longitude 0<P to 78D west, and Atitude S= to IV north. Your correspondent "Beruaritn" in mistaken in saving they are to north of Vcnecncln.such being impossible, since the Carnbean Sea K-Hshes the shores ot Venezuela on the north, the -Umate here is very unhealthy for Europeans. Doraorara :>einR tho capital of British Guiana, the most westerly md adjoining Venezuela.—J. G.

TS933.1—LOAM PANS.—Having becu troubled the fame as " Inquirer," I discovered that there was too much clay intheloam.audatter the mould was blackwashed and smoothed over, I tame over it all with barm, <.r very stale beer, put on with a very line brush ; this lias the douhlo effect of staying it from vetoing, and tho blackwash from scaling.—N. L.

P3982.]— SOAP-MAKING.—Some valuable information on this subject is to be found in Dr. Ure's " Dictionary of Arts and Manufactures."—Beta.

[3982.]—WORKS ON SOAP-MAKING.—" Campbell "Morntt on Soap and Candles," cost about £2; "Ott ou Soapniaking," cost about 10s. (id.; " Kurten ou Soap-making," «-.jst unknown. All to be got through Triibuer & Co. The two first are the highest authorities on the subject, and arc exuaustiu- and well illustrated; the last is good and practical, tilt the translation (from the German) is tanltv. many errors in substances, measures, and ■weights, which would puzzle a novice, though not difficult of correction by a practical hand at the trade.—D. G.

[4020.]—WOUI.FFE'S BOTTLE.—Let " M. P. C. 8." <-linck a piece of ordinary brass tube in a lathe (say) 2in. or 3in. long, and its external diameter slightly less than the internal diameter of the neck; now, whilst tho tube is in rapid motion, press tho part requiring to be cut out gently against the end, using emery and oil, or flue sand and water, as a cutting or abraiding medium. It will bo found a great advantage if he can manage to apply the pressure through the medium of a piece of iudia-rubber held against the inside of the bottle; this will cut it out quite clean. The same plan is applicable to cutting tho central hole in electric discs, Ac. A very neat application of it is to cut opeuiugs opposite to the wiudiug centres of shade-covered pipe pieces; these openings can be protected by inserting a small brass bu$h or ilft with a little white lead, a great brass plug being used to keep out dust. Under those circumstances the shade never requires to be lifted, as the winding, Ac., can be effected by the application of a suitable key.—Matuix,

[4022.1—TUNING BELLOWS FOR HARMONIUM. —See "Elcve's" letter, p. 186, ante.Saui. Rymea.

[4042.]—MAGNET.—Nos. 16 or 18 would answer.— Sigma.

]4i)44.]—AIR GUN.—The drawing represents the lock and breech screwed together. A A lock, B spring, C trigger, D tumbler, E sear, F F push pin, G trigger spring, H *.ear spring. III seats for the upper plate, "romoved to show the construction. Tho triggor and sear work on studs riveted into the plate, and prolonged through the upper plate, screwed down by a single screw, which aUo serves to check the motion of the sear. J section of breech, K valve, L brass tube. The valve rod within this tube lias a spiral spring along its length to keep the valve to its seat: the valve is best made of bullock's hoof. The lock is represented ready to be discharged. The barrel—not shown—is on the other side of the

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chief merits are—first, acompleto scale; second, a single sound to each kev, whether drawn ont or compressed, thereby dispensing with tho the thumb-bellows of German concertinas. I have heard very difficult music excellently performed on theso instruments by Mr. W. H. Birch, of Reading, who is, I believe, musical editor for Boosey & Co., Holies-street.—J. Nasu.

[4006.]— SODA WATER.—TO" F. C. S."—Tell me if two strong-hooped barrels would stand the pressure; and what material tho bottling and corking apparatus should be made of: and what length of time it would take to impregnate the water with the gas; and what he ni'-ans bv a washing vessel botweou ?'Auy information he can give will bo th.inkfu.Uv- received. I tried tho uuslackcd lime, and it was o,uitc a failure, which I knew it would be.—D. W. L.

[4102.1 —GALVANISM.—Dr. AHhims's work is, perhaps ,e best on medical electricity, price 15s.. obtainable through any booksellor. My next paper wiU deal with the galvanometer question.—Szgxa.

[4121.]—BOTTLING FRUIT.—Take any quantity of fruit that is sound and fresh; till your bottles ; tiU a copper nearly fuU with cold water, with a b..ard at the bottom; put the bottles in. up to their necks in tho water; put it ou the lire, and let tho heat get up to 150 degrees; let them stand at that heat for twenty iniuutos, then tako them out, and fill tho bottles with boiling water; then bung them, and tie with a bladder, and they wiU keep any longth of time if kept air-tight.—D. W. L.

[4136.]—EGG-HATCHING MACHINE.—" P. G. M.,-' who asks for information in detail ou this subject, wiU Hud an illustration of Pinchen's Incubator on p. 108, Vol. X., of our Mechanic-. It has, I believe, been found successful. According to M. Reaumur, all that is required is a heat of 96J Fahr. Eggs kept at that temperature for the requisite number of days will produce chickens. Mr. Cantolo, however, who some years ago exhibited what he called a hvdro-iucuhator, assorts that the proper temperature is lu6;;Fahr.; and if this heat is sustained chickens will sometimes appear on the eighteenth or nineteenth dav. His machine wascapable of hatching from 100 to 600 eggs; and its principle consisted in aUowing warm water to flow along plates of glass placed over the eggs. The Egyptian and Chinese systems are much the simplest, as in these tho eggs are merely placed in trays of sand or bran, and kept in ovens or on heated iron plates. It is very doubtful whether any system can be made profitable in this country.—Saul Rymea.

T4144.J—FIRECLAY BAKING.—The raw fireclay is usually mixed with one-third its weight of burnt fireclay termed "grog," or powder of old glass pots from which all the clinker, 4c., has first boen carefully removed. Sometimes a certain proportion of saud is added, or clays, other than Stourbridge, according; to circumstances and the purposes to which the clay is to be applied. This mixture is moistened, kneaded, and let stand for some time; often a fortnight or threo weeks, receiving occasional kneadings in the meantimey the longer you can let it stand and the more thoroughl. it is mixed the bettor the clay. When the articles are made they are allowed to dry gradually in a warm room]; when they are very thick, throe months are often aUowed tfor* this operation; they are then transferred to an oven and raised to redness. Tho more slowly this drying and baking takes place the loss the liability to crack. In somo cases fireclay crucibles are not previously burnt or baked before use. In tho ease of pots used" for casting steel it is found that if tho pots are burut with the mouth downwards they do

from only semi-double flowers, and will forward " Saul Rymea" some if heVillgivo me his address. It w is saved from a few single that grew witk some a, uue double oue3 as any one could wish to see having spikes of flowers from 9in. to fciiu. long, be-ides a mass of side branches: they are what wo in Sussox caU the Giant stock.— Norma.

[4273.]—SPLITTING WHALEBONE.-The blades previous to cutting are softened by boiling for a couple of hours in a long copper. They are then fastened edge upwards in au ordinary wooden' bench vice, and planed by the subjoined tool. A B are two handles, 0 D is an iron plate, with a guide-notch E; F is a semicircular knife, screwed firmly at each end to the iron plate C D, having its cutting edge adjusted in a plane so much lower than the bottom of the notoh E as tho thickness

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of the whalebone is intended to bo ; for differout thicknesses tho knife may bo set by tho screws at different levels. The workman holding the tool by the handles applies the notch E at the end of tho whalebone blade furthest from him, and pulls it gantly along so as to shave off a slice in the direction of the fibres, care beiug taken not to cut across any of them. Those slips are afterwards dried, and planed level, and are polished with ground pumice, felt, aud water. I do not know where "Enquirer" can obtalu whalebone: but it is brought from Greenland in pieces containing ten or twelve blades. Thebladosare sometimes separated and cleaned by the saUors of the whaling ships. The price varies from £50 to £150 per ton.—H. U.

[4279.]—GAS METERS.—Asa maker both of wet and dry meters, I, with all due deference to Mr. H. Newton, prefer the former for exactitude and durability. Not to extend unnecessarily my letter, I will quote Clegg's work, (no mcau authority):—" The opinions of gas engineers continue to be divided as to the relative merits of dry aud wet meters; but for accuracy of registration, when the water is at the proper level, the wet meter is not surpassed, if it bo equaled, by any other."—E. Wellahd, Bordeaux.

[1311.]— RULE WANTED.—lib. of cast iron contains 3*84 cubic inches; hence tho cubic contents of any cast body in inches, divided by 3-84, will give its weight. Elucidation of examplo:—60 x 3-81 = 23040 cubic inches in the block aud 9 x 14-5 = 130-5; hence the cubic contonts 230-40 -r-130-5 = 1-76SS1 + inches thick. —W. Drihcoll.

[4316.]—A DIFFCULT QUESTION.—I do not see that there can be any doubt about there being first the inside tube 12" diameter, gripped by a second tube, hoop, or ring, 18" diameter, and this second ouo gripped, in its turn by a third, with an eight ton grip.—Unit.

[1322.]—SEWING MACHINES.—It is rather difficult to say exactly what tho cause of "H. W.'s trouble is, as the effect ho describes may bo caused in one or two wavs. There may uot be sufficient tension ou the top thread or the little brush is not properly adjusted against tho hook.—Unit.

, [4356.]—SOFTENING SKINS.—If flowers of sulphur be mixed in a littlo milk, and after standing au hour or

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plate A A ; it is of brass, carefuUy bored and polishod. In constructing an air cane, be sure the reservoir is sufficiently stout, aud made of copper, that the brass collar into which the breech screws fits accurately, and is weU soldered. The butt end should be brassed up, not tinned. Further details if requested.—T. A.

[4072.] — HARMONIUM QUERY.—As "Eleve" is doubtless too busy to answer queries just yet, I am sure ho wiU pardon me for treading on his ground, especially as I shall merely teU "Valve" what I have been told by "Eleve." The reed holes for 8ft. tone should be liiu. by 5-16in. at base; and 9-16in. by 3-l(iiu. at treble. The paUot holes should be liu. by fin. at base, aud .tin. by 3-loin. at treble, of course graduated as regards length aU the way; and tho pallet holes should be Jin. wide to

afi but tho top octave—tj?., thirteen notes.—Saul,

Rymea.

[4076.]—NATURAL SELECTION.—This doctrine, which is gaining general acceptance among the leading minds, is that the many varied species of plants and animals are gradually developed from a few simpler forms by natural processes; that the surrounding conditions of good climate, &c, produce modifications and those are perpetuated which suit the varied conditions. Tho idea really is that nature does just what man does when he produces new varieties. 'How far the process is to be considered to extend is doubtful; some people are terribly afraid of the doctrine, under the idea that it does away with creative action; whereas, it rcaUy means that the creative power is everywhere present, always active now and for ever, instead of acting once for all. When fuUy developed and rightly understood, it will bo found to teach as the Great Teacher taught, that tho sparrow faUs not to the gronud unheeded by its Father and ours; that each springing need, each blado of waving grass, and the humblest insect, whose life is but a summer day, is part of a great whole pervaded by the universal life, of which these different forms are the actions and development.—Stoma.

[4092.]—THE ENGLISH CONCERTINA.—Sinco no one else replies to "Lost," aUow me to say that the English concertina is really a good instrument. Its

not crack, but if with tho mouth upwards, they do The " grog "or burnt fireclay is added to form a sort of skeleton, as it were, and thus prevent the tendency to crack.—An Associate Of The Royal School Of Mines.

[4206.] — CHROMATIC FAIRY FOUNTAIN.— "Q. Q. R." evidently does not understand Prof. Tyudall's experiment. When a ray of light, passing from water into air, strikes the surface at an angle greater than what is called the "limiting angle of refraction "—viz., about 43" 27', it is "totaUy reflected;*' but this does not occur when the angle of incidence is less. In the falling Btreara the ray is continually reflected in this mauner along tho stream, thus (seeFig. 1); but, in the

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arrangement proposed by " Q. Q. R.," the my would evidently very soon strike the surface at a much les? angle, or, indeed, perpendicularly, and would accordingly pass through into the air without reflection: the falling water could not, thereiore, be illumined.—IiiNoitAKT

IRISHMAN.

[4226.] — DOUBLE STOCKS.—In my humble opinion (although only an amnteur) the best plan to get seed tor double stocks is to pick off from tho single ones every flower that has only four petals, saving only those with fiveaud six petals,oh what a florist would call scmidonblo, which will produce weed that will come nearly all double. I have now got some seed nearly ripe, saved

two the milk (without disturbing the sulphur) he rubbed into the skin it will keep it soft. Care should be taken uot to prepare it too long before using, as tho milk is apt to becomo putrciied. Perhaps the above mixture may not answer " Country Vct.'s" purpose, as it is used to soften the skin (human) and improve tho complexion. Yet he can give it a trial if he chooses, as its cost will be very sinaU.—Kansas.

~ [4359. (—AMBER BEADS.—Amber boads maybe rcpolished with whitening and water, or rottenstone and oil, finishing in cither case with friction alone. Ambor mav be known from meilito (honey-stonel and copal, both of which are sometimes substituted for it, by the agreeable odour it omits when burning, and by tho greater electrical power it possesses after friction; mellite is infusible by heat.—T. W. Boord.

[4361.]— METHYLATED SPIRIT.—"T. L. H." is in error when he savs turpentine is added to spirit, to form methylated spirit.—An Associate Of The Royal School Of Mines.

[4361.]—METHYLATED SPIRIT.—This is a mixture of 90 parts of spirit of wine (S.G. -«30), duty free, and lo parts of wood spirit (methyl, alcohol, or carbinol). It cannot be used for medicinal" purposes or beverages on account of its ropulsive taste and odour; but lor many of the purposes for which pure spirit of wine was formerly used, such as tho preparation of varnishes, polishes, chemicals, the preservation of museum specimens, Ac, it forms an efficient aud cheap substitute.— Beta.

[4363.] — LIMEWASH ON MASONRY. — " Agent should use a weak mixture of spirits of salts, or muriatic acid, and water.—Beta.

[4364.]— DRYING SMALL WHEELS.—A small room or cupboard heated by a gas stove would bo the most economical, though I should imagine that auy U^i^K process would be apt to cause thorn to twist.—T. W. Boord.

[4365.] —INDICATOR DIAGRAMS.—" Fireman," in order to calculate indicator diagrams, must divide thorn into at least ten equal parts by lines drawn at right

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