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plicity and efficiency? Suppose a turbine that is propelled by the water being simply thrown against wings and buckets (without collecting the water in a chamber as in on engine for instance) is used, what horse-powerjor fraction of horse power could thus be gained, and should the water be allowed to flow out of the full size pipe, or should the end be contracted, and if contracted what would be the best size of outlet ?—J. Johnson.

[47&*VJ — STEREOTYPING.—Will any reader kindly inform me of a plan of making the moulds for stereotyping, so that they can be used immediately they are made, the moulds I make (of starch and whiting) having to stand some time to get into condition?— Amateur Stereotypes.

[4785.]— BINDERS' TOOLS, Etc.—Will " Ab Initio," or some other contributor, be good enough to tell me where I can obtain a binders' pattern-book of rolls, Ac., as I have applied to many houses and cannot get one? Will " Ab Initio" also bo good enough to state in what Nos. of our Mechanic, I shall find his recipes for staining leather, &c. ?—L. J. W.

[4788.]—IMPRESSION OF FERN LEAF.—Will some kind reader inform me as to the best method of taking the impression of a fern leaf?—Inquirer.

[4787.]— SPEAKING TUBES.—Having witnessed the laying down of a galvanized iron speaking or whispering tube, the bore of which is lin., and length 600ft., the completion of which turned out a failure, I am anxious to learn as to the best material for such a purpose, and to what length it id possible to go, so as for each communication to be distinct.—Inquirer.

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Model Mills, p. 430.

Destructive Soap Powders, 430.

Emigration, 430.

Rocking Chair, 480.

Cleveland Ironstone, 430.

Sizing, 430.

Polariscope for Lantern, 430.

Want of Pressure, 430.

Stone for Trinkets, 431.

Black Glass- of Antimony, 430.

Lancashire Black, 480.

Hollow Candles, 430.

Draught Furnace for Smelting LeBcl Ore.

La Crosse, 480.

Windmill for Working Lathe, 431.

Cracked Boiler Plates, 481.

Concertina, 431. 4349 Heating House with Hot Air, 431. 4850 Barometer, &c, 431.

Case for Ferns, -181.

Weaving, 481.

Copper Medal, 454.

Coil, 454.

Galvanizing Nails, 454.

Condensing Water, 454.

Insects in Water, 454.

Re-enamelling Zinc Clock Dial, 454.

The Hautboy, 454.

Printing, 454.

Shell Gold, 455.

Supposed Ancient Painting, 455.

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DISINFECTANT FOR SCARLET FEVER. — A homely,but apparently most usefuLmethod has been communicated to us {foihi Journal) for disinfecting houses and rooms in which cases of scarlet fever have occurred. Dissolve saltpetre up to the point of saturation, and in the solution soak several sheets of coarse blotting paper, which must be allowed to take up as much as they can, and be afterwards dried. Carefully close every door, window, and chimney of the affected room, and let the prepared blotting paper bo lighted and smoulder itself out. This is of courso not intended to supersede the use of Condy's fluid, the value of which in every household where there is sickness is sufficiently well known; but we have heard of such success in checking the spread of infection by means of the saturated paper, and it is moreover so easy of trial, that we gladly publish the information sent to us.

THE ADVANTAGES OF SCIENCE.—Chemistry, therefore, in its highest, and, it may be said, its most theoretical investigations, is most justly to be cultivated by a nation. In an ordinary sense the resources of a nation lie in the growth of its soil, as well as in the minerals which the soil contains, and likewise in the fish of its rivers and of its seas. Holland, limited in its soil, and destitute of minerals, sought in fisheries and in whaling other materials for wealth, which have been the foundation of her shipping and carrying trade. It was, however, by the applications of science that Holland, in a less progressive age than this, endowed herself with further resources and constant employment for her population. By a better application of politico-economical doctrines she enlisted skilled labour; favouring the per* secuted, she attracted capital; protecting the Jews, she raised her public and private credit as an assured means of providing herself with wealth. Holland, by free trade in corn, was the entrepot of Europe, and became the great money market. By the prosecution of chemical and mechanical studies, then favourably fostered by the possession of the great book and publishing market, Holland promoted every branch of manufacture, acquiring a supremacy over the world In manv departments. If Holland has no lougor the monopoly of these advantages, it is because the late war fell heavily upon her; and that other powerful nations, particularly our own, are engaged in the same career, leaving Holland only a minor share—Food Journal,

ANSWERS TO CORRESPONDENTS.

*,* All communications should be addressed to the Edttob of the English Mechanic, 81, Tavistockstreet, Covent Garden, W.C.

The following are the initials, Ac., of letters to hand up to Tuesday morning, September 6, and unacknowledged, elsewhere:—

R. M. 8., S. & eo., W. Pickering, Dr. T. C. Burton, J. A. Mays, Godwin Emberey, W. Hunter, Timothy Bnrstall, J. R. T., Magog, Rich. Harvey, R. A. P., W. Pocklington, H. Dolon, W. Kummis, R. Gay & Co., W. M. E., A. B. C, C. B., J. Grafton, R. J. Jones, D. H. Tho mas, T. G. A., T. R. P., J. Y. and Son, D. D., W. H. S., Revd. E. H., R. A. Proctor, Jas. MilLs, J. Jarman, A. Underhill, E. L. G., R. Evans, J. C. Frank, Feu Follet, Aplanatic, Geomotroa, Dr. U., J. W. S., R. W., Excelsls, R. P. E., Rev. J. H., 8. Wright, Dr. J. B., Lieut. II.. B. H. T., Jas. Mills, H. Drinkwater, 8. and Co., Anon. Roanoake, Chas. Goodyear, H. C. Sutton, C. Tiesset, W. T. H. Beechey, J. J. B., Beginner, W. J. Eggleston, F. H. Rogan, The Harmonious Blacksmith, W. J., Onus, Thos. Fletcher, An Old Man, Engraver, An Attic Worker, J. W. T., T. D., H. B. M., Boniface, Pater Familias, J. B. Fenby, Geo. E. Davis, F. A. B., Salt, Toincter, G. 8. Walsden, Thos. Wood, Hat, Wahsrof, W. D., H. Dolan, A Contributor, A Publisher's Clerk, R. E. H. Gotfiu, T. P. Bnrkas. Suffolk Amateur, Operator, George Stedham, W. E. Yates, Ed. Sharpe, J. T. M., Amicus, Pace, J. W, Yarmouth Bloater, J. B., E. T. S., W. T.Laber, J. T. W., F. P. P., Student, Improver, E. V., D. Jacob, J. Brown, Blaok Country Joe, L. M. N., T.Storey, J. Nash, J. Thomas, George, Dcedalus, A Poor Clerk, Judas, B. W. J., C. F., Wood, C. B. T., O. P. Q., R. N., George Hardy, Rev. E. Kernau, Oliver Cromwell, W. Greenwood, Amateur Astronomer, J. W. G., F. G. A., Liliputinn, Young Phrenologist, E. M., Eli Green, J. T. H., W. B.

"coal Measure Fossil," by T. P. Barker, next week.

"Speculuxi Working," by J. P., next week. The Bicycle.—Jas. Smith, E. Hamley, E. T. J., and others have written letters in vindication of bicycle riding. All speak of the journeys they have gone on the bicyle with remarkable ease.

The Phantoh Wheel.—We have received sevoral more letters in answer to the "Harmonious Blacksmith," ail showing, from practical experience, that that coi respondent was wrong in stating that these wheels lacked rigidity.

Holiday Time.—Though it is holiday time when many correspondents are enjoying themselves by the i easide, on the river, or on the moors, correspondence flows into our office in a continuously increasing stream. Lot it flow on. The larger the postiuans bundle the better we are satisfied, and the richer will be the contents of every succeeding number. An unusually large number of letters, queries, and replies are necessarily postponed till next week.

II. O. asks to whom application should be made for employment as Clerk of Works under tho Turkish Government. We should think to the Turkish Embassy, Bryanston-square, London.

"Mounting For The Microscope " by Achromatic, next week. Please send name so that a paper may be sent.

Eostace His Ton Jones on " Organs and Harmoniums," next week.

J. T. H.—The half-penny postage system, will begin on the first of October next.

J. H. 8.—For prices of timber and other building materials see the " Timber Trade Review" weekly in tho Building A>?rj.

Accessories To The Microscope next week.

F. F. C. aays, " I mnch regret that In writing fttont my dislike to the flute, I should have made us* ot expressions which have excited the indignation of a ckrfrman." "F. F. C." says his reverend censor U more guilty than himself in perpetrating the fault b- himself condemns.

Lex, who does not send his address, is mightily offended because we did not insert his answer to " R. p„" *b.um he charged with " deliberate equivocation" and "-(rnstr ignorance," and like a petulant child who breaks Uie toy he does not understand, he ceases to be a subscriber. He says " the loss yon have sustained by not publishing my letter is small (Ave subscribers), bat if other letters are similarly treated yon will ultiiml-i\ awaken to a sense, &c." We shall continue to tre&t absolutely discourteous correspondents in the san* manner, if wo lose five or five thousand subscriber., as we know very well that we should get 10,000 m«n subscribers in their place.

F. Jordan.—A puff nevertheless.

A. M. Keays.—We can't say. Have nothing to do with doctors who advertise questionable works.

J. R. M.—See Needham's "Starter for Sewing Mi. chines," p. 233, this volume.

J. R. K.—The number was sent. We cannot be re*pu= Bible for Post-offioe losses or irrefrnlaritiea.

J. M.—The query appeared and waa answered.

T. W.—Crocus Is the commercial name of a poli&huif powder made with oxide of iron.

Chemicus— No; it was M. Sobrero who discovered iiu properties of nitroglycerine, bat M. NobeL the Swedish engineer, first brought it into notice (o.blasting purposes.

Courteous Correspondence.—We have referred abo^r to a letter from " Lex." How different in the folio ing from a correspondent whom "Lex" abuse* .Sir,—I feel very sorry that any part of my letter or

"Handwriting" should have given offence to " Lex" or

any other correspondent (see "Answers to Correspondents," p. 576). I have frequently been onsr.

dieted in your columns on matters which I ban

known to be true, and after writicjg an angry rrpjr,

have destroyed it, rather than yield, to my ttet/Ur or

temper. Your valuable pages sborxld be the ifcn

house of accumulated thought and experience, art .

receptacle for auKry feeling. May every reader Hit

the same pleasure that I do in extending the cirenk.

of the English Mechanic.SoriptoR.

Compensated Balance.—" Seconds Practical Nisi maker" has promised to contribute an Aqskt U< query.

Mr. Glass.—We don't know the address.

Jones.—See reply about" Adept," in " NoBYw U> Comspondents" last week. To second am «loa B. Willis, No. *

Steel.—Your query on " Soldering" hast«*aKs*ael again and again. What metals?

Dr. Maclaren, Blairgowrie.—An American puMjeafe*.

Conbtant Reader.—If you made your siphon mpartaa before the one at the Workman's £ihioition *«a patented, you may sell yours, or as many of the same kind as you like.

W. Herd.—Don't know the address.

H. Boon.—Nothing is charged forthe insertion of queries
of course.

F. H. Roberts.—Apply to the Secretary ot tin Bwiish
Mechanics' Scientific Societv, Working Men'iCoBep,
Manchester.

Astron.— Nearly every number in Vol. X. conUini letters on telescope construction. Those that «iU most likely suit you are 236,288. 240, 243, 344, 445, Ml. All of these can be obtained of the publisher.

D. Hoffmann.—This sign (;) is known to all printers, type-founders, and bookbinders as a "double dagger."

J. T. Rowlands.—Apply for the specification at tht Patent Office. None of our readers are likely to know anything about it, unless theyhavo already purchased the specification.

G. Harvey.—Tho dials of the clock at the House* * Parliament are 23ft. iu diameter.

Old Craulington.—Try the furnlturn creams fro on p. 525, (4150). Most oilmen sell tticm ready nori

N- V.—Tho subject of sewing machines has beenils»i exhausted in our columns. See Vol. X, pp 3rB, Si Vol. XI., pp. 90,112, 157, 2 i 1. 231, 280, 875.

J. H. Gray.—See a recipo m Vol. X. p. 56.

G. P-—No. "Systolo" means literally "a bricfis together, and is used bv medical men to denote ti" action of the heart which expeU the blood ikii! dtaBtole " means " a placing asunder," and it vJ to explain the contrary action, as when tht Mo* enter* the heart.

G. B. D.—" Weight of ball" answered by seven! emspondents previously. Please supply nurow •■ replies in future. By so doing you will save u, Belabour.

W. 8. Husk.—The "unclaimed prizes" were not tot* ferredwhen the Mechanic was incorporated wiiala English Mechanic.

D!i*'F?^Th0 8u«888tod articles on brass would v doubt bo instructive and acceptable.

B. E. LoDDY.-The writer of the articles on the '• Work man sExhibition" went to the war as a special corns spondent of a morning paper. Like manv others be was arrested ami imprisoned. He has, however returned and probably .will resume his criticism on Ihf exhibition. Tho price of the catalogue is6d.

i Hos. Marshall.—As you wrote saying the repiv was incorrect it was destroyed. *'

Trinitrophenic, who auswers two queries in to-dsT« impression, says, "He shall be happy to answer any "ther questions relating to chemistry."

W. E. D.—Exchange advertisements were made 6d. for two reasons. 1, to establish a uniformitv of price, ano: 3, to act justly, as many people were coutinuall.tryirjK toget" for tale" advertisements in the exchange

^//"/iT*?8" ??" wbaI° "eloiuja to and forms an or.Ier of the class Mammalia. You are perfectly correct in call n? it a "aea-animal." Tho class Mammalia in

i i) « "». animals which suckle their young.

"■"■—Mountain soap is a mineral, soft to the touch, wnieh assumes a greasy lustre when rubbed, and "Us to pieces in water. It is found in the Isle of aaye and in Bohemia. Analysis shows it to consist of 44 parts silica, 26-6 alumina, 20-5 water, oxide of in>n 8, Urn's 0-5. It is known by the same name in both t reach and German—tavon dc monlat/ne and Brrntei/e.

<ih^ (ftitjjHsh Hffcclrank

AND

MIRROR OF SCIENCE AND ART.

FRIDAY, SEPTEMBER 16, 1870.

RECIPROCAL GEOMETRY.
By J. Beverley Fenby, C.E., M.I.M.E.

IT very frequently happens that those who have to make geometrical calculations for practical purposes are at a loss for the proper formula for some particular case, and are therefore under the necessity of referring to a pocket-book for something which they require. No matter how retentive the memory of any engineer, or how thorough his training, it is impossible for him to carry all necessary formulae in readiness by memory alone, hence the need of some form of pocket-book. In many cases, however, there is some reciprocal relation existing between that which he has "at his fingers' ends " and that which he does not at the time remember, which would, if known, obviate all doubt. Some time back, a draughtsman employed under the writer had to deal with a problem in the designing of some machinery, involving the calculation of the cubic contents of a spheroid. As to the proper mode of performing this calculation, the draughtsman—though a very well informed, and withal industrious youth—was evidently at sea, for, after looking for some book, which he failed to find, he applied to the writer for the requsite formula.

Inquiry elicited the fact that he was perfectly well informed as to the method of finding the contents of a sphere, and also that he had on more than one occasion worked out the problem as regarded the spheroid, but without noticing any special relation between the two. The writer of this memoir, in place of giving him the formula for the spheroid as an isolated one, gave him a comparison between the contents of the cube, parallelopipedon, sphere, and spheroid. With these relations he seemed much struck, and expressed his surprise that such reciprocit y in geometry was not pointed out in every work on the subject. Further researches on this subject brought to light the fact that not only were standard treatises silent on the subject, but that very well-known men actually, at first sight, denied that the alleged reciprocity existed. The fact that men accustomed to performing calculations had, in so many cases, missed the very beautiful principle of reciprocation which runs through geometry naturally aroused the writer's attention, and led to the compilation of the following notes on the subject. Before commencing to explain the reciprocations hereafter stated, it may be well to state that it is not supposed that any original discovery is here embodied, but merely that practical men have overlooked a fact that would materially lessen the labour of calculation, as applied to geometrical figures, such as constantly crop up in practice. It must, therefore, be clearly borne in mind that this little memoir is intended solely to aid practical men in performing calculations, and not as an exercise for mathematicians. The geometrical figures to be treated of are (1) the square j (2), the oblong; (31, the oircle; (4), the ellipsis; and the solids directly derived from them—namely (5), the cube; (6), the parallelopipedon; (7), the sphere; and (8), the spheroid; and the object aimed at is to show how the mode of calculating each of these figures is reciprocally related to all the others, and thence to prove that it iB easier to remember them as a group verv closely related than to take them disjointedly as is done in the ordinary text-books. T0 theproposed mode of consideration, it may be objected that the eight figures enninerated belong to three Jjranches of geometrical science, namely 'plane geometry, the geometry of solids, and conic sections. As an abstract question, this is undoubtedly true; but in practice these three branches are promiscuously mixed; and as we only propose to deal practically with them we think no valid objection exists to treating them in their reciprocal relations; the more so as a just comprehension of their affinity to each other will very materially help the student in understanding their properties and, therefore, in appreciating each in its just>ir -e t he three great branches of geometry.

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jacent sides, as A B, B C, thongh the oblong diners only from the square in having its opposite sides equal to each other, but wanting the equality of the whole four. If now we take the case of a circle—inscribed for the sake of illustration in a square—we find that the area is obtained by multiplying the two diameters of A B and C D together (Fig. 8.), by which we obtain the area of the circumscribing square, and then reducing the product by multiplying by the factor '7854; which in effect reduces the area of the square abed by the sum of the parts A a C, C o B, B d D, and T> c A, the excess of the square over tho circle. Inasmuch C jf

as the two diameters A B and C D are equal, this rule is commonly given as though only one diameter were multiplied by itself or squared. The consideration of the ellipsis will render this self-evident. To find the area of the ellipsis in Fig. 4. the diameter A B is multiplied by the

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diameter C D—by which we obtain the area of the oblong a b c d—and this area is reduced by multiplying by the factor '7854, so as to deduct the Bum of the parts A a C, 0 6 B, B d D, and D c A; that is the excess of the area of the rectangle over that of the ellipsis.

If the reader has carefully followed the cases given he will easily perceive that we have shown that the area of the square and that of the rectangle are found by identically the same process, namely, by multiplying two adjacent sides together. He will also perceive that the area of a square circumscribing a circle is first calculated to obtain the superficial contents of the circle, and that the latter area is simply -7854 of the former.

Further, it is observable that tho are a of an ellipsis is deduced from that of the circumscribing rectangle by multiplying by the factor .7854. The results, then, which wc have arrived at maybe stated as follows ;—First. The area of the square and that of the oblong are obtained by identically the same process, namely, tho multiplication together of two adjacent sides; the squaring of one side in the case of the Square being an accidental consequence of the equality of all its sides, and in no way affecting its properperties as a rectangle. Secondly. The area of the circle is deduced from that of the sqnare, and the area of the ellipsis from that of the rectangle, simply multiplying by the same factor, namely, •7854. Hence the square is to the oblong as the

circle is to the ellipsis, at regards area; and to calculate these Four figures it is only necessary to renumber Two facts, namely, the multiplication of two adjacent sides—or the diameters at right angles—and the factor-7851. If, therefore, the student will impress these simple reciprocal relations upon his memory be will perfectly master four very useful facts in practical geometry.

Passing from the consideration of these fonr plane figures to that of the solids derived from them, we find the same beautiful laws of geometrical reciprocity to hold good. From the square is derived the cube, and its solid contents are found by cubing one of its

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have the contents by exactly the same process iw

for the cube. Following out the principle we

started with we find that, as the cube is generated

from tha square and the parallelopipedon from

the oblong, so are the sphere from the circle and

the spheroid from

the ellipsis. Further

we find that tho

contents of the sphere

are capable of de

ductiou from those

of the cube, and

those of the spheroid

from those of the

parallelopipedon. Let

Fig. 7 represent a

sphere inscribed in

a cube, and Fig. 8 a C ~

spheroid in a parallelopipedon.

To find the solid contents of the sphere A C B D we will conceive the three diameters A B, C D and E F to be multiplied together. The result is

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evidently the solid contents of the circumscribinjr cube, and the multiplication is equivalent to the process of cubing the diameter of the sphere on the side of the cube. The excess of the content* of the cube over those of the sphere is reduced hr multiplying by the factor -5230, which practical!/ turns off the corners of the cube. Extending the analogous processes to the next case, that of the spheroid, we find precisely the same iule holding good. To find the solid contents of the spheroid, ABCD, Fig. 8, the ordinary rule ir to multiply the stationary diameter A B by the square of the revolving diameter C I), and then by the factor '5286. This is equivalent to multiplying the stationary diameter A B by the tw« diameters C D and E F; the latter being n

right angles to each other. This process gives j ns the contents of the parallelopipedon a b c defg, anil the reduction of this by the factor -5236 used as a multiplier gives the contents of the enclosed spheroid. In Fig. 8, a prolate spheroid is shown, but the principle holds just the same with the oblate spheroid.

The relations we have traced may be thus summarized:—

Firstly. Consider the sqnare and the oblong merely as rectangles, and lor the area multiply two adjacent Bides together (these two being equal in the /square).

Secondly. Remember the factor -7854, and for circle or ellipsis multiply two diameters at right angles (observing that these are equal in the circle, and that the major and minor are to be taken in the ellipsis); the area—which is that of the circumscribing rectangle—will, when multiplied by the factor, give that of the circle or ellipsis, as the case may be.

These two cases embrace the four plane figure* of which ice are treatingnamely, the Sqvaue,

OBLONG, CIRCLE, and ELLIPSIS.

Thirdly. To find the solid contents of any cube or parallelopipedon multiply any three sides which give the length, breadth and thickness, and the product will give the result required.

Tilt: Cube until differs from other ParallelloIipedons iii having All its sides equal.

Fourthly. Remember the factor ■5286, and, for the solid contents of the sphere or spheroid, multiply three diameters together; observing that in the sphere all these are equal, while in the spheroid two only are equal, and these are of necessity revolving diameters. This multiplication gives the contents of the circumscribing cube or parallelopipedon, and the reduction of the result by the factor '5236 used as^a multiplier will give the contents of the sphere or spheroid.

It will therefore be seen that precisely the same mode of calculation may be traced through these eight cases, thus: For the plane surfaces named two dimensions are multiplied together—namely, length and breadth, and for the solids denoted these are further multiplied by the thickness. That for the circle and ellipsis the factor -7854 is used as a means of reduction from the rectangle corresponding; and for their solids, the sphere and spheroid, the factor -5230 as the measure of reduction from the cube and parallelopipedon. When onco these reciprocal relations are mastered it is only necessary to burden the memory with the retention of the Two factors -7854 and -5230 to be completely mastor of the areas and solid contents respectively of Eight of the most important figures in practical geometry. To be thoroughly au fait at calculating these eight figures is thus a very simple acquirement, but not the less useful to the practical man; and yet what proportion of the total number possess this knowledge, ready at a moment without any book for jogging the memory? If called upon for an answer it must be eonfessed very few ; in fact most look upon the ellipsis and spheroid as very recondite figures to deal with. The present little memoir has been written with the aim to show that it is not an abtruse question to deal with any of these figures. Beyond this its intention does not reach; it is in fact a purely simple and practical synopsis of the points touched upon, and if it should help any of the readers of the English Mechanic to a ready ease in dealing with the calculations treated of, its purpose will ho fulfilled.

came to my mind."* From these low hills on the N., and from the interior bases of the moun-J tain border, the surface of Fracastorius gradually rises so as to form a slightly convex floor, which culminates in what has hitherto been considered as a small central eminence or peak, but ascertained by Mr. Ingall, on the morning before-mentioned, to consist of two craterlcts, which, for easy reference, may be designated a. These craterlets arc interesting, inasmuch Br from them, in a S.W. direction, a line of very minute craterlets (appearing in ordinary states of the atmosphere and in smaller instruments as a streak of light! extends to a craterlet b on the S.W. part of the floor, which I observed with the Hart well Equatoreal on Sept. 13, 1862. From this latter craterlet another chain of minute oraterlets extends to a craterlet c, south of the pair u already

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By W. R. Birt, F.R.A.S.

ON the southern border of the Mure Nectaris (V of Webb's index map) when the moon is about five days old, will be found au object appearing immensely like a buy, indeed any one of the bayB on our own sea coasts—Torbay, for example—will furnish a fine terrestrial analogue. The name of this object, 372 of Webb, is Fracastorius. Surrounded on the W., S., and E. by a high mountainous border, the enclosed surface is separated from that of the Hare Nectaris by a range of very low hills, which appeared to Mr. Ingall (who observed them on the morning of July 17, 1870, with a dialyte of 51in. aperture, powers 196, 236, and 768) as if the soft mud (?) of the Mure Nectaris had flowed and almost covered somo high mountains there, and had rounded off the asperities as if they had been washed with it. Mr. Ingall adds, "this is somewhat romantic, but I express my ideas as they

mentioned. This craterlet I observed on July 11, 1865. In addition to these objects Mr. Ingall ascertained the existence of another craterlet, d, on the W. part of the floor, similarly connected with the pair a by a chain of minute craterlets, interrupted by a larger craterlet c, first seen by Mr. Ingall on July 17, 1*70. So far as I am aware these minnte crater chains have not hitherto been detected. Clefts have been observed within the interiors of lunar plains surrounded by mountain borders, but these in Fracastoriut are so analogous to the well-known crater chains W. of Copernicus, that further.observation of them is extremely desirable, especially with large instruments.

There arc two features of interest on the floor of Fracastorius—viz., a line of craterlets a little E. of the centre, and another a little E. of the W. border. These appear to be two nearly parallel lines of eruption, except at their S. ends, where they converge to a crater on the S. border of Fracastorius, given by Beer and Miidlcr, seen by me on July 11, 1865, and by Mr. Ingall on Jnly 17, 1870. The first line of eruption consists of five craterlets, the southern one m seen bv me Sept. 13, 1862, and by Mr. Ingall July 17, 1870. The next is the craterlet c, already mentioned, the third and fourth the pair a, and the fifth is a craterlet/, seen by me July 11, 1865, and by Mr. Ingall July 17, 1870. It is given by Beer and Miidler. The direction of this line is nearly N. and S., and it terminates with a low mountain '/, with at least three peaks, which I observed in 1862. 1863, and 1865, and Mr. Ingall in 1870. It would appear that between this mountain and the low hills forming the north border, indeed close upon them, is a somewhat shallow crater, seen by me on Sept. 22, 1868, and again on April 5, 1870. The second line of eruption consists of four craterlets and two spots of light )/. The craterlets are 6, d, and a pair of minute craterlets h. This line is terminated by tvo spots of light a. as seen by Mr. Ingall, on July 17, WO. These spots I have usually seen, 1862, 1863, and 1865, as one, which is described in my earlier observations as "a round-topped table-land." On Sept. 21, 1H68, there was certainly not the slightest appearance of a hill or table-land, no bright side, no shadow. On the 22nd Sept., 1868,1 recorded "a round white spot is plain." July 1. 1865, Mr. Groverdescribed the object as "a crater." Mr. Ingall, July 17,1870, speaks of it as a doubtful object, which appeared as a double-light spot having no shade. Between the mountain g and the spots v, is, in Mr. Ingall's drawing, July 17, 1870, n hill o answering to the "round-topped table-land" mentioned abovo in appearance but not in position. Mr. Ingall depicts three pairs of craterlets, the pair a of medium size, the pair h very minute,

and a larger pair i and k on the E. part ol itn floor, rather widely separated and hitherto asreeorded. Between these and the crateriew s ii smaller one /, also unrecorded. The apr/cum? of Fracastorius on Rutherford's photngrea,, March 6, 1865, is extremely interesting. B dark tint of the Mare Nectaris has penetrate*) the interior of the floor; indeed the matera' this portion seems to be of the same natc.. that of the surface of the adjoining Mart, ■, tinuing its outline on the S., while the comas of the two dark surfaces is interrupted b>b#s N. border of Fracastorius, which is of *£&• reflective power. A somewhat short rita.the S.W. border, given by Mr. Ingall, est?. this description of the floor of Fracast* > very interesting lunar formation, which P. to afford results bearing as much on impc selenographical questions as those obtained* the study of Flato, if its craters' spots ande ings be observed with the same assiduity wL has characterized the observations of FlaU;

'Although Mr. Ingall's analogy of soft mud, *c, is not likely to bo accepted by astronomers, nor is it put forth as supporting any theoretical view, it certainly expresses the idea of "invasion from the Maria," which is fullv borne out by the appearances presented by all suoh formations as Fracastorius.

MOUNTING FOR THE MICROSCOPE.

By "Achromatic."

IN laying before the renders of the Eioia Mechanic some articles upon mounting in the microscope I must beg to apologize to Ik other writers on the same subject for seendssir treading on their heels. In treavting this s»l>j«: I shall speak of the apparatus required is OSjunction with the method of mounting the o!>j«t which may be under discussion , hoping br lix means to avoid all ambiguity ass to what insfnincuts, Ac., are required. And liere I nut option that most of the apparatus and a great nai.v of the instruments can be very effectire'r mi« factured at home, as also can iniiumeraii-'t Utile knick-knacks, the same designed by (Bengal"* inicroscopist, to snit occasions rente)! uoa his method of treatment, which as of pi«a* practised will bo found, in all likelihood, to considerably differ from that of a brother in the artIu treating insects in my nrs! ctajiter, tk advanced state of the year musf he my eicnsi. and let me remind the beginner that he shouli lose no time in gathering specimens for future treatment.

Chapter I.

PREPARATION OF IXSECTS.

Insects, like hares, have to be caught beiorf they are " cooked," and this fact makes it im perative for the microscopist to make little acursions into the country (if he can), into a tow garden, or even into bis cellar, and in fact anywbaf where insects most congregate. And then tk insect having been caught has to be killed, id for this nothing is more handy than a j»uK death-bottle, made thus :—

To Make A Death-bottle.—Having eaass* largo mouth stoppered bottle of a size to w'. clean it well, then drop into it three «^m good-sized lumps of potassic cyanide (hull » ounce of this salt will be quite sufficient for • large bottle), cover completely with dry al>» sand, and on the top pour a plaster nuvlf "> plaster of Paris mixed with about half its bull "silver sand. Pour a thickness of this from iw to three-quarters of an inch; when ••set"is cover over the surface of the plaster withi J*" of loose blotting or nlteriug paper, cnt *"*'' nearly fit the bottle. This is a perfect «*•' bottle.

Besides this, I should recommend a Boi*' ono to be made, small enough to be- e»rt*k about ou the person at all times. This will t1 found extremely useful and convenient, fur »aj little insect that we may come across durins th» day can be immediately consigned to omivii* without the least trouble; and in this way <& supply of insects will be found to bei great*! augmented.

The insect being now killed, should bo passei on to the next stage—that of the potash—sa\>posing that it is to be mounted whole ; if, however (as is more generally the case), itis to be dissected, a proper book should bo cousulted, to ascertaiu what parts are the most desirable for preserv* ticn, and then the insect being dissected, ii accordance with this knowledge, these parts, awith the whole insect, are to be iinmerHe.il iii caustic potash.

But to dissect, certain instruments are required Of these I think the scissors must be purchased, but small dissecting knives can be made by grinding sewing needles to au edge, and then

(ranting them in conveniently sized holders of dnr or other wood. Of oourao these knives Ji be made of any size or shape to suit con mionce.

In addition to the knives, plain mounted needles various dagreeti of fineness, a few of them being nt (the bending should be done to suit circiimances), will be found extremely useful, nud inied necessary.

The potash nsod in this stage should l>e made 1 the following way :—

To Ptiepare Potash For The MicnoscorE.—To be liquor potassre of the pharmacopeia add its wn bnlk of water.

It will be fonnd in practice convenient to have arioft3 bottli»s of potash of different strengths to uit the texture of the different subjects for prearutiou; generally three are sufficient.

The timo that ap object should be left in the ausitic potash is a matter best determined by iractiee, but a little consideration will be found of Teat service, it being kept in mind that this lkali, while it dissolves flesh and fatty matter, eaves horny matter unacted upon. The subject having been left in the potash for time sufficient to extract all fat, &o., is imtiersed in as pare water as possible for four-andwenty hours, the water being changed from two o four times during that period.

The object being taken out of the water should >e well brushed with a copious supply of water. rhe best brush for this purpose is a large camel's-hair brush, costing one penny at any oil■<hop. With the brash the future object should be arranged, according to taste, on a clean glass slide, and another clean slide being placed upon it, the whole is placed in some convenient contrivance for squeezing it firmly together. When dry, the object is carefully removed from the slido and immersed in good clear methylated spirit, where it is allowed to remain for three or four days to extract the last trace of moistnre. The beginner need not be afraid of the spirit taking the form out of the object. From the spirit the object should go into methylated ether for two or three days, and if there bo any bnbbles of air in the object, it should be allowed to remain till they disappear. The object should next bo soaked in the best refined turpentine for a couple of days; ;it the end of that time it may bo considered fully prepared.

The object may now be mounted, and for this, of course, two glasses and a medium are required. As to glasses the thick slides had best be bought r..»dyout, the nnground ones costing 4d., the ..-ouud Nd. a dozen; but if preferred, the thin ylass can be bought in sheets aud cut at home, uad, perhaps, with a small saving; but this saving is so small that it will hardly be found worth the risk of breakage, always incurred by aii amateur. The medium for insects is generally Canada balsam, costing tid. a bottle.

To mount the prepared object a clean slide ^.iould bo placed on a piece of paper with its own ntre marked thereon, and the object being taken from the turpentine, by means of the forceps, is laid over this centre, and all superfluous turpentine is wiped off with a dry caniel'shair brush. A drop of balsam on a pointed glass ivi.l is then let fall upon it, and a thin glass cover, nicely cleaned, is warmed, anil being held by the forceps, is allowed to fall on the balsam, one side being more depressed than any of the others; the whole is then gently heatedover a spirit-lamp, w a candle, when it will be found that the cover will fall down on the top of the object as the balsam softens by the heat. The cover should tben be gently squeezed down with the top of the needle holder, aud to keep the cover in its position till the balsam hardens a spring clip should be used. The superflous balsam should not be cleaned away in less than a month from the tune of mounting, aB it is apt to shrink and so idrait air bubbles under the glass cover. This is rar mounted object, and if care has been taken ( ought to be good; no dirt, no bubbles, and no Itnineas ought to be visible. As for its not being erfect, in the sense of complete, that is owing I bad manipulation, and is not a fault of the ethod of preparation.

The above process may, perhaps, be considered ttsand tedious, but it is really not so; that to have to wait a long time for the completion thu preparation I admit, but then it does away ta aU necessity for au air-pump for extracting '-bubbles, &c, for with a little care air does not id cannot (by reason of the object, up to the ymg process, being filled with some liquid or ner) get in. If, however, it does get in a few } 8 extra in the ether will generally drive it

out. In this, as in other things, the beginner
must remember that it is practieo that makes
perfect.

(To be continued)

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THE THEORY OF SUNSTROKE.

R. E. VAN DE WARKER, writing in the yew York Medical Journal, thus explains the cause of sunstroke:—The integrity of the cutaneous function is essential to the maintenance of the equilibrium of the thermal condition of the body. The perspiration is one of the principal avenues of escape for the surplus heat generated by the operations of organic life. While this is true of the body when in a quiescent state, it becomes a cardinal truth when the body is in a state of exertion and exposed to an elevated temporaThe healthy man, when exposed to these

ture.

conditions, at once perspires, and the temperature
of the system is preserved at a normal standard. If
this means of compensation between the systemic
heat and that of the surrounding air is impaired,
heat musi accumulate in the system in reciprocal
proportion. To use a familiar illustration, the
evaporation of perspiration from tho surface of
the body lowers its temperature in the same
manner as the evaporation of water from the sur-
face of heated iron.

When tho body is exposed to intense solar heat,
the perspiration is the direct antagonist of the
sun's rays. When wo reflect upon the amount of
heat necessary to evaporate one ounce of water,
it is easy to see how the arrest of this function
may lead to serious or fatal lesion of the vital
fluids or nerve-centres. An ounce of water pass-
ing from the fluid to the vaporous state receives as
much heat as would raise its temperature to 'J'M
Fahr.; or, the quantity of heat required to con-
vert a quantity of water into vapour is live and a
half times as much as will raise it from the freez-
iug to the boiling point. The evaporation from
the surface of the body of one ounce of perspira-
tion would transmit from the system to the sur-
rounding air all the heat required to accomplish
its evaporation. On the contrary, tho arrest of
this secretion would lead to the retention in the
system of the heat otherwise expended in the con-
version of it from the fluid to the vaporous state.
The other excretory functions boing impaired, it
would obviously require but a short exposure to
an elevated temperature to lead to an ac-
cumulation of a morbid degree of heat.
This is not au immediate effect; it is pro-
gressive. The impairment of function goes on
with the impairment of strength. The exhausting
march, or the stoking at tho furnace, or labouring
in the field, is still continued, aud, before the
victim is aware of it, possibly, the skin has ceased
entirely to act. There are now but few avenues
of escajw for the systemic heat resulting from
muscular action, from the oxidation of tissue, or
from the hajmal oxidation of normal alcohol present
in the lungs, and still less escape from the alcohol
the man too often takes to relieve tho exhaustion
from which he is suffering. In addition to this,
from the sun's rays the body is continually absorb-
ing heat, until such a degree of heat is present in
the system, that disorganization of the blood re-
sults, or the nerve-centres are so oppressed by its
presenco that insolation (sunstroke) results. I
therefore conclude that insolation is the ex-
pression of tho presence of a morbid degree of
heat in the organism dependent mainly on tho
arrest of the cutaneous function.

Tho preventives recommended by Dr. Van do Warker, are tho wearing of a white shirt over tho ilannel, if that is dark coloured, covering the neck and chest, and wearing a light straw or palmleaf hat, with fresh leaves or a wet handkerchief in the crown. Tho working man should always attend carefully to his diet, and never work exposed to a high temperature while suffering from the calls of hunger. Ardent spirits should be avoided. The violent reaction following over-stimulation is attended with most serious effects when the subject is exposed to a high temperature. When men experience a sense of fulness in the head and of tightness across the chest, with a total or partial suppression of the perspiration, they ought immediately to stop work and protect themselves from the Bun's rays until the functions of the body are restored. Persons in infirm health or convalescent ought to take extra precautions when exposed to severo heat.

NEW SALT FOR INTENSE ELECTRIC
CURRENTS.

METEVE, of Paris, has taken a patent for ■ the composition of a Bait for the production of very intense currents of electricity, which he calls double acetate of iron and potash. The inventor claims to remedy the inconvenience arising from nitrous exhalations disengaged from solutions of nitric acid, in the following manner:— The nitric acid is replaced by a salt composed of one part of sulphate of protoxide of iron and one part of nitrate of potash, dissolved in a sufficient quantity of the ordinary acetate of commerce, tho solution being aided by a slight heat; the whole is then left to cool and crystallize, and the crystals after being drained, are stove-diied. When the salt is thus prepared, the pile is mounted in the following manner:—In the "non-porous vessel is placed a saturated solution of common salt, aud a zinc cylinder is introduced, within which is placed the porous vessel containing tho charcoal, npou which is poured water containing 31) per cent, of sulphuric acid. In this state the pile will not act, or in an almost insensible manner; but, in order to develop the current, it is only necessary to introduce a few crystals of the above-named double salt, when the current becomes remarkably intense, if not superior to that of the common pile; the current may be easily maintained constantly and regularly by merely adding a few crystals from time to time, and without any nitrous vapours being disengaged. M. Etevo believes that his salt is a double acetate of iron and potash, but a writer in the iloniteur ScitHitiiinue objects to this, and says that if small quantities of this salt are formed, as is probable, with tho aid of the acetic acid, the greater part consists of two sulphates and two nitrates of potash and iron. He believes that the activity of the salt in question arises from the fact that the small quantity of the acetate of protoxide of iron, finding itself in the presence of a nitrate of tho same metal, becomes peroxidized; heat as well as electricity will bring this about. This is the salt that has proved of so much value in the dyeing of black silk, and which is improperly called nitro-acetate of iron. All who have attempted to reduce nitro-benzine by ferrous acetate know howrapidly this converts nitric acid into ammonia. Gun-cotton may also by it bo brought back into the natural state of cotton. It is, therefore, quite natural that no nitrous vapours should be evolved from a pile fed by such salt. Perhaps nitrate of soda might be substituted for nitrate of potash with economy.

Sixty-nine thousand one hundred and twenty flowers are wanted tor 5U0 gramme* ol gaurou.

THE FLUTE AND ITS VICISSITUDES.
By Sable.
(Concluded from page 553.)

THE alleged improvements of the Bbhm flute awakened "great expectations" iu the minds of flute-players generally; but all pleasant anticipations were at once dispelled by the appearance of the instrument itself, and with few exceptions its introduction was strongly opposed: it was accompanied, too, by a number of new students having little or nothing in common with the staid Nicholsonians, who treated the old flute with contempt, voted it "obsolescent," and answered all opponents with the full, firm tones of the Bbhm. This was rather too much tor the old flautists, tome change and remodelliug they had expected, some fresh difficulties they were prepared to encounter; but here was a metamorphosis in which thoy could recognize nothing of their old acquaintance save its head, aud even the fashion of that had been altered: here was a flute to be studied afresh from its very gamut; something to be acquired and something to bo forgotten simultaneously: moreover, it was pertinently objected that what had already been so changed aud complicated would in all probability undergo further mutation at no distant period. Meanwhile, the new instrumentalists gained ground, and the old stagers, who would not go to school over again, either eschewed the flute altogether or retired disspiritedly from the contest; hence all not personally interested in the matter ceased to study the Hute, and the popularity of the old favourite at once declined.

The reader is referred to Fig. 1, the Bbhm flute, the drawing of which shows the opeu C natural, or thumb key e; the open G sharp key <; next claims attention, and the open B flat key b, acted upon by the lever of tho ring a, second

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finger of left hand, also by rod of the ring r, first finger of right hand; thus to produce B flat the first fingers of each hand are pressed dou n; the ring c also closes /, the open F sharp key, in fingering F natural; and the ring rf, third finger of right hand, shuts / by the aid of the lever in producing F sharp. The awkwardness of these B flat and F sharp fingerings to a flautist of the Nicholson school can only be duly estimated in their acquirement. It is scarcely necessary to apologize for the open-keyed system; every fluteplayer is aware that the tone of the instrument is much improved by keeping the D sharp key open when it can be done (in rapid arpeggios in the chord of F natural, when the F natural key can be "secured"—e.g„ as when E and C do not occur in the passage, the increased fulness and freedom with which the flute speaks is very evident, especially in the fundamental octave). Such was the Bohm, or first open-keyed flute, practically useless to those who would or could not begin as upon a new instrument. A carefully made drawing is given, it having played so important a part in the flute's history, and it is the foundation of that system which has been applied not only to all modern flutes, but to all instruments of its genus. That distinguished professor, the late Mr. Clinton, was one of its earliest and warmest advocates. After comparing its system carefully with that of the old flute, he was so convinced of its superiority that he adopted it himself and recommended it to his pupils; but in doing this he encountered B Btonu of opposition. "However," he writes, "those who were my most vigorous opponents, after a while became my warmest supporters; and I was confident that the decided superiority of this flute would eventually overcome the prejudice with which it was at first regarded." The open G sharp key, nevertheless, was found to be so troublesome that M. Dorus, of Paris, changed it into a shut one, adding the ring for the left hand third finger. This change was adopted by Mr. Clinton, in 1842, and slight as it was it gave rise to more dissatisfaction and suspicion. Herr Bohm had " astonished the natives " with his invention, a Mr. Cornelius Ward, how ever, surprised both natives and foreigners with the very singular species of flute, and he increased their surprise by assuring them in a pamphlet that on his system facilities were offered by sundry cross and back fingerings: it is true that this flute was professedly free from such abominations, but be it ever remembered, that all departures from the old mode of fingering (which is decidedly the best because based upon simple and natural Uwb) is practically a back or cross fingering. Mr. Ward's contrivance had five keys for the work of the left hand thumb, three of which acted on the foot keys; they were in reality apologies for " duplicates," to obtain slurs, &c, not available before, and the result was that neither the old or new were accomplished well; this flute was to dazzle all the orchestras in Europe, but its fame was circumscribed, its existence brief, and it is scarcely remembered. A drawing of this musical curiosity would have been presented, but that it served no useful purpose in flute regeneration. A Mr. Card next presented himself with a flute that was to "make these odds all even,"—it was neither more nor less than the "Bohm" in which the right hand part was altered, while the left remained as before; this died almost in its birth and was soon thrown aside. The next claimant for favour was the flute of Mr. Biccama, B.A., formerly known as the " Diatonic," and it did good service to the cause inasmuch as it reverted boldly and steadily to the old system of fingering; it possessed many advantages over the Nicholson flute, but they

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were insufficient to displace the Bohin, the Dorus modification of which still held its own both in England and on the Continent. Fig. 2 is an accurate representation of the "Diatonic or Siccama" flute; there are two finger rings at d which command the open key between them, by which arrangement the C sharp is much improved in tune and firmness; there is a finger plate at a which closes the open key covering the G hole, and at b is a similar contrivance for " stopping" the E hole (as both these openings are placed beyond the reach of the finger), which decidedly improves the respective notes. The F natural key is also situated lower in the body of the flute. In this instrument the same theory of equal-sized holes is strenuously maintained, although it is turned " on strictly acoustical principles." "The weak and ineffective quality of several intervals on the old flute, occasioned by the disproportionate size of the holes, and the inequality of their respective distances, is entirely remedied on this flute, where they are of an equal character throughout and partake of the same firmness and power." "For A an aperture equal in size to the preceding ones,—thus a clear and brilliant A is obtained," &c, &e, Now if all these tine theories be right, dame Nature mutt have made a rare hash of her acoustics! but seriously; it proves what a fascination equalsized holes have bad for flute manufacturers. In the interim, pockets were lightened, and the purse of the exchequer made heavier by tho patents granted for all these contrivances; Ante players were dissatisfied and undecided, and makers worked up to a great pitch of competition and contention, each one earnestly affirming that his instrument was the "werry identical flute," and all others were "abortions." M. Tulou, of Paris, added another faggot to the fire by substituting two thumb keys, one for C natural, and the other for B flat. And now the talented Mr. Carte, in conjunction with Messrs. Rudall * Rose, brought out two new flutes, and in a thoughtful treatise, lucidly stated the fact that the flute's condition was as yet highly unsatisfactory. Mr. Clinton appears to have applied to the patentoes of the Biihm flute on the subject without avail; however, he went to Munich to consult with Herr Biihm, who, some little time after, brought over his metal flute with parabola head (like the clarionet) but it did not meet the difficulties in the estimation of the former gentleman. One would have imagined that the Bohm flute, in the hands of a proficient, was all that could be desired, but it was not so; players of moderate capacity, it is true, found it certain ease in getting out the lower notes, but the intelligent student soon discovered the host of evils with which he had to contend; the notes of the third octave were painfully sharp and thin in quality, owing to the largeness of those apertures serving for the time as "vent" holes; the lowest note (C natural) was a very fine one, the D, immediately above it, weak; the whole temperament of the cylinder very unequal; there were several veryawkward fingerings, and a deal of work imposed

upon the weak fingers. TLie cylindrical i n brought forward as a new thing; it »Mnot n. files and the old flute a bee (p. 411, W b.m con structed so long before; the conical head joist was no novelty, the clarionet nd oreii PP' were old examples of crocs in the heads of aMfical tubes. Under these drrzm.<ia»«s, Mr. Clinton himself commenced i »srwe of ciperimeuts, the result of which w as ertafe date with the simple and natural expedient otrtjiuViy graduating the holes. Fig. 3 shOTsU* *•>>■■ with its equal-sized holes; Fig- 4. the ** ■" with regular gradations. It a true «&■*■" declared that cylinder flutes with graduate* t^ were made by them prior to the appemaiss » the "Clinton cylinder," and that the saiUidecreased regularly "always one qusrta * B millimetre" (about l-105in.) "in diuaAs Be this as it may, such a gradation wouU ■* no practical influence on tone or tune, even icould be accurately marked on the flute's nm surface. It would be beside the purpose to commend any particular flute, but if we artto have what has been so patiently and ■> triously sought, I think we have got it ia Sr Clinton Cylinder; nor are spectacles needed to b" us that the natural laws of sound have not *•■ violated; the old system of fingering is tear and the long cramp F natural key discir* there is also B means of taking this note wfc' first finger of the right hand, as on the N, but this involves no alteration in the fingers » the F sharp, or the old fingering of the forar; My task is done, and I have to acknowleii;i care and accuracy with which my drawing a been reproduced; and I must, en pasw»teiP* my admiration of the beautiful engnrif • machinery, which are constantly given * !B periodical. And now I bid adieu to the S*47' of the English Mechanic with heatf M" wishes both for themselves and Out f*"^ Although no longer able to use or enjori'"V the satisfaction of knowing they cu*?j i Finally, I entreat all to believe thatf*1***" steadily in mind the motto which k*k ^ papers—

Nothing extenuate,

Nor aught set down in mabce.

Erbata.—P. +59, 26th line from bottom-*" ."* raid " his." P. So8, 39th hue from top—for " B" hm."

The End.

COFFEY'S APPARATUS FOR DIST
TION.

AS several correspondents have asked f<
formation concerning Mr. Coffey's A
inventions of apparatus for distillation, ev*|
tion, ifec, we give an illustration of a porti
that in use by Messrs. Doulton tt W»t*
Lambeth. The invention of Mr. Coffey
in the application of the discovery that a so
paraffine oil may be continuously heated in d
tubes to a temperature of 1100" Fa'ur.—in
words, to a temperature at which iron exbi

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