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pliolty and efficiency? Suppose u turbine that is propelled by the water belag simply thrown against wings an d buckets (without collecting the water in a chamber as in an engine for instance! is used,what horsc-powcrjor fraction of horse power conld 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.

[4784.]—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 1— Аилткип Stereotyper.

[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, 4e., 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, Ac. ?—L. J. W.

[4786.]—IMPRESSION OP FERN LEAF.—Will somo kind reader inform me as to the best method of taking the impression of a fern leaf?—Inqcireh.

[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 is 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, 430.

Cleveland Ironstone, 430.

8izing, 430.

Polanscope for Lantern, 430.

Want of Pressure, 480.

Stone for Trinkets, 431.

Black Glass of Antimony, 430.

Lancashire Black, 480.

Hollow Candles, 430.

Draught Furnace for Smelting Lead Ore.

La Crosse, 480.

Windmill for Working Lathe, 431.

Cracked Boiler Plates, 431.

Concertina, 431.

Heating House with Hot Air, 431.

Barometer, &c, 481.

Case for Ferns, 481.

Weaving, 481.

Coppor 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 usof ul,method has been communicated to us (Food Journal) for disinfecting houses and rooms in which cases of scarlet fever have occurred. Dissolve saltpetre up to tbc 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 be lighted and emoulder itself out. This is of course 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 и-,

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, ав well as in the minerals which the soil contains, and likewise in the Ûsh 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 persecuted, she attracted capital; protecting the Jews, she raised her public and private credit as an aesured means of providing herself with wealth. Holland, by free trade in corn, was the entrepôt 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 cverv branch of manufacture, acquiring a supremacy over the world In many departments. If Holland has no longer the monopoly of these advantages, it is because the lato war fellheavily 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 Editor of the English Mechanic, 81, Tavistockstreet, Covent Garden, W.C.

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F. F. С says, " I mnch regret that in writing about my dislike to the flute, I should have made use of expressions which have excited the indignation of a clergyman." "F. F. C." says hie reverend censor \~. more guilty than himself in perpetrating the fault he himself condemns.

Lkx. who does not send his address, is mightily offended because we did not insert his answer to " R. P.," whom he charged with " deliberate equivocation" and "groes ignorance," and like a petulant child who breaks the toy he does not understand, he ceases to be a sabscriber. He says " the loss you have sustained by not publishing my letter is small (five subscribers), bot if other letters are similarly treated you will ultimately awaken to a sense, Ac." We shall continue to treat absolutely discourteous correspondents in the same manner, if we lose five or five thousand subscriber», as we know very well that we should get 10,000 more subscribers in their place.

F. Jordan.—A puff nevertheless.

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

J. R. M.—See Needham's "Starter for Sewing Machines," p. 232, this volume. J. R. K.—The number was sent. We cannot be responsible for Post-office losses or irregularities. J. M.—The query appeared and was answered. T. W,—Crocus is the commercial name of a polishing

powder made with oxide of iron. Chkmici 's.—No; it was M. Sobrero who discovered the properties of nitroglycerine, but M. Nobel, the Swedish engineer, first brought it into notice fur blasting purposes. Courteous Correspondence.—We have referred above to a letter from " Lex." How different is the following from a correspondent whom "Lex" abuses:

Sib,—I feel very sorry that any part of mv letter on "Handwriting" should have given offence to'" Lex" or any other correspondent (seo "Answers to Correspondents," p. 576). I have frequently been contradicted in your columns on matters which I have known to bo true, and after writing an angry reply have destroyed it, rather than yield to my tempter or temper. Your valuable pages should be the storehouse of accumulated thought and experience, not a receptacle for angry feeling. May every reader take the same pleasure that I dorn extending the circulation of the English Mechanic—Scriptor. Compensated Balance.—" Sec»nds Practical Watchmaker" has promised to contribute ao answer t^ query. Mr. GiBBS.—We don't know the address. Jones,—See reply about " Adept," in " Notice? to Correspondents" last week. To second query about H. Willis, No.'

Steel.—Your query on " Soldering" has been answered

again and again. What metala? Dr, Maclaren, Blairgowrie.—An American publication. Constant Rea Der.— If you made vour siphon aquariuwi before the one at the Workman's Exhibition was 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 for the insertion of queries of course.

F. H. Roberts.—Apply to the Secretary of the Euglish Mechanics' Scientific Society, Working Men's College, Manchester.

Astron.—Nearly every number in Vol. X. contains letters on telescope construction. Those that will most likely suit you are 236,288, 240, 243, 344, 345, 247. All of those can be obtained o/ the publisher.

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

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

G. Harvey.—Tho dials of the clock at the Houses of Parliament are 22ft. in diameter.

Old Chamlington.—Try the fornitura cream? given on p. 525, (4459). Most oilmen sell them ready mixed.

N. V.—The subject of sewing machines has been almost exhausted in our columns. See Vol. X, pp. 362, 32(1 VoL XL, pp. 90,112, 157. 2 Li. 231,280, 375.

J. H. Gray.—See a recipe in Vol. X. p. 56.

Ö. P.—No. "Systole" means literally "a bringing together," and is used bv medical men to denote that action of the heart which expel« the blood, whilst "diastole " means " a placing asunder," and is used to explain the contrary action, as when the blood enters the heart.

G. B. D.—" Weight of baU" answered bv several correspondents previously. Please supplv numbers to replies in future. By so doing you will save us much labour.

W. 8. Husk.—The "unclaimed prizes ■ were not transferred when the Mechanic was incorporated witb the English Mechanic.

Duffer.—The suggested articles on brass would no doubt be instructive and acceptable.

B. E. Loddy.—The writer of the articles on the "Workman's Exhibition" went to the war as a special correspondent of a morning paper. Like manv others he was arrested and imprisoned. He has, however, returned, and prubablv.will resume his criticism on the exhibition. The price of the catalogue bod.

Thor, Marshall.—As you wrote saying the reply was incorrect it was destroyed.

Tbinitrophenic, who answers two queries in to-day's impression, says, "He shall be happy to answer any other questions relating to chemistry."

W. E. D.—Exchange advertisements were made 6d. for two reasons. 1, to establish a uniformity of price, and 2, to act justly, as many people were continual!»trying to gel " for tale " advertisements in the exchange column.

8. Г.Р.—Yes. The whale belongs to and forms an order of the class Mammalia. You are perfectly correct in calling it a "sen-animal." The class Mammalia includes all animals which suckle their young.

J. B. M.—Mountain soap is a mineral, soft to the touch. which assumes a greasy lustre when rubbed, and falle to pieces in water. It is found in the Isle of S ivo and in Bohemia. Analysis »hows it to consist of 44 parts silica, 26*5 alumina, 20-5 water, oxide of iron Й. lims 0*5. It is known by the same nume in both, French and German—moondt tnontajne and Bergreife.

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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

fret

r, C z

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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 us the contents of the parallelopipèdon abc de/g, and the reduction of this by the factor -5236 need as a multiplier gives the contents of the enclosed spheroid. In Fig. 8, a prolate spheroid is shown, bnt the principle holds just the same with the oblate spheroid.

The relations we have traced may be thus summarized :—

Firstly. Consider the square and the oblong merely as rectangles, and lor the area inultiply two adjacent sides 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 arc 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.

Tlieue two cases embrace the /our plane figure* of which we are treatingnamely, the Souahe,

OBLONG, CIRCLE, and ELLIPSIS.

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

The Cube only differs from other Pakallellorii'EDONs in 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 aro equal, while in the spheroid two only are equal, and these are of necessity revolving diameters. This multiplication ¡lives tho contents of the circumscribing cube or parallclupipedon, 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 -5236 as the measure of reduction from the cube and parallelopipèdon. When onco these reciprocal relations are mastered it is only necessary to burden the memory with the retention of tho Two factors '7854 and -6236 to be completely master of the areas and solid contents respectively of Eioht 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 oonfessed 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 au 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 bo fulfilled.

TELESCOPIC WORK FOR MOONLIGHT EVENINGS.

By W. B. Bibt, F.R.A.S.

ON the sonthem border of the Mare Nectnris (V of Webb's index map) when tho moon is about five days old, will be found an object appearing immensely like a bay, indeed any one of tho bays on onr 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 ¿lure Xectaris 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 o^in. aperture, powers 196, 236, and 768) as if the soft mud (?) of the Mare Nectaris had flowed and almost covered some high mountains there, nnd liad rounded off the asperities as if they had been washed with it. Mr. Ingall adds, "tliis is somewhat romantic, but I express my ideas as they

came to my mind."* From these low hills on the N., and from the interior bases of the uioiuiy 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 craterlets, which, for easy reference, may be designated a. These craterlets are interesting, inasmuch ns 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 Hartwell Equatoreal on Sept. 13, 1862. From this latter craterlet another chain of minute craterlets extends to a craterlet c, south of the pair « already

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mentioned. This craterlet I observed on July 11, 1865. Iu addition to these objects Mr. Ingall ascertained the existence of anwther craterlet, <i, on the W. part of the floor, similarly connected with the pair a by a chain of minute craterlets, interrupted by a larger craterlet e, first seen by Mr. Ingall on July 17, 1870. So far as I am aware these minute crater chains have not hitherto been detected. Clefts have been observed within the interiors of lunar plains surrounded by mountain borders, but those in Fracastorius arc so analogous to the well-known crater chains W. of Copernicus, that further.observation of them is extremely desirable, especially with large instruments.

There are two features of interest on the floor of Fracasturius—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 linos of eruption, except at their S. ends, where they converge to a crater on the S. border of Fracastorius, given by Beer and Miidler, seen by me on July 11, 1865, and by Mr. Ingall on July 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 Mädler. 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, nnd Mr. Ingall in 1870. It would appear that between this mountain and the low hills forming the north border, indeed close npon 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 и. Tho craterlets are o, d, and a pair of minute craterlets A. This lino is terminated by tiro spots of light я, as seen by Mr. Ingall, on July 17,1870. These spots I have usually seen, 1862, 1863, and 1865, as onr. which is described in my earlier observations as "a round-topped table-land." On Sept, 21, 1868, there was certainly not the slightest appearance of a hill or table-laud, no bright 6ido, 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,.Inly 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 », is, in Mr. Ingall's drawing, July 17, 1870. a hill i) answering to the "round-topped table-land" mentioned above in appearance but not in position. Mr. Ingall depicts three pnirs of craterlets, the pair a of medium size, the pair A very minute,

and a larger pair í nnd к on the E. part of the floor, rather widely separated and hitherto unrecorded, between these and the craterlet e is a smaller one /, also unrecorded. The appearance of Fracastorius on Rutherford's photogram of March 6, 1865, is extremely interesting. The dark tint of the Mare Sceleris has penetrated to the interior of the floor; indeed the material of this portion seems to bo of the same nature as that of the surface of the adjoining Мате, continuing its outline on tho S., while the connection of the two dark surfaces is interrupted by the iow N. border of Fracastorius, which is of a higher reflective power. A somewhat short ridge near the S.W. border, given by Mr. Ingall, completes this description of the floor of Fracastorius, a very intt-resting lunar formation, which is likely to afford result*; bearing ns much on important sclenographical questions as those obtained from the study of Flato, if its craters' spot* and markings be observed with the same assiduity which has characterized the observations of Plato.

* Although Mr. Ing-all's analogy of soft mud. Ac is not likely to be Accepted by astronomers, nor is it put forth us supporting япу theoretical view, it certaiuly expresses the idea of "invasion from the Maria," which is fullv borne ont by the nppearanoes presented by all such for .nations as Fracastorius.

MOUNTING FOR THE MICROSCOPE.

By "Achromatic."

IN laying before tho readers of the English Mechanic some articles npon mounting for the microscope I must beg to apologize to the other writers on the same subject for seemingly treading on their heels. In treating this subject I shall speak of the apparatus required in conjunction with the method of mounting the object which may be under discussion, hoping by these means to avoid all ambiguity as to what instruments, &c, are required. And here I may mention that most of the apparatus and a great man v of the instruments can be very effectively manufactured at homo, as also can innumerable little knick-knacks, the same designed by the ingénions inicroscopist, to suit occasions resulting from his method of treatment, which as he gets mote practised will be found, in all likelihood, to considerably differ from that of a brother in, the art. In treating insects in my first chapter, the advanced state of the year must be my excuse, and lot me remind the beginner that he should lose no time in gathering specimens for future treatment.

Chapter I.

PBEFAJtATION OF INSECTS.

Insects, like hares, have to be canght before they are "cooked." and this fact makes it imperative for the microscopist to make little excursions into the conntry (if he can), into a town garden,or even into his cellar, and in fact anywhere where insects mo6t congregate. And then the insect having been caught has to he killed, and for this nothing is more handy than a pocket death-bottle, made thus :—

To Make A Death-bottle.—Having chosen a large month stoppered bottle of n size to suit, clean it well, then drop into it three or four good-sized lumps of potassic cyauide (half an ounce of this salt will be quite sufficient for a large bottle), cover completely with dry silver sand, and on the top poor a plaster made of plaster of Paris mixed with about half its bulk of silver sand. Pour a thickness of this from half to three-quarters of an inch; when "set" firm cover over the surface of the plaster with a piece of loose blotting or filtering paper, ent so ns tu nearly tit the bottle. This is a perfect deathbottle.

Besides this, I should recommend a smaller one to be made, small enough to be camel about on the person at all times. This will bo found extremely useful and convenient, for anylittle insect that we may come across during the day can be immediately consigned to oblivion without the least trouble; and iu this way onr supply of insects will be found to be greatly augmented.

The insect being now killed, should be passe I on to the next stage—that of the potash—supposing that it is to he mounted whole ; if. however (as is more generally the case), it is to be dissected. a proper book should be consulted, to ascertain what parts are the most desirable for preserva tien, and then the insect being dissected, iw accordance with this knowledge, these parts, awith the whole insect, are to be immersed íl caustic potash.

Bnt to dissect, certain instruments are requiitnl Oí these I think the scissors m«vl be purchased, but small dissecting knives can be mude by grinding sewing needles to an 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 c, first finger of right hand; thus to produce E Slat the first fingers of each hand are pressed down; the ring с also closes /, the open F sharp key, in fingering F natural; and the ring d, 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 flute- player 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"—c;/,, 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 Böhm, or first open-keyed flute, practically useless to those who wouid or could not begin as upon a new instrument. A carefullymade 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 a storm 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 a 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 Böhm had " astonished the natives" with hi* invention, a Mr. Cornelius Ward, however, surprised both natives and foreigners with a 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 profesnedhjtree 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 laws) 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, A.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 a "Böhm" 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. Siccama, 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

[graphic]

were insufficient to displace the Böhm, 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 h 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 tuned "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," Mi &c. Now if all these tine theories be right, dame Nature must have made a rare hash of her acoustics! but seriously; it proves what a fascination equalsized holes have had for flute manufacturers. In the interim, pockets were lightened, and the purse of the exchequer made heavier by the patents granted for all these contrivances; flute 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 С natural, and the other for B flat. And now the talented Mr. Carte, in conjunction with Messrs. Budall <fc 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 patentees of the Böhm flute on the subject without avail; however, he went to Munich to consult w ith Heir Böhm, 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 Böhm 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 a 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 very awkward fingerings, and a deal of work imposed

upon the weak fingers. The cylindrical bore was brought forward as the new thing; it was not so; jije* and the old flute a bee (p. 411; had been constructed so long before; the conical head joint was no novelty, the clarionet and огдап pipes were old examples of crocs in the heads of musical tubes. Under these cirenmstances, Mr. Clinton himself commenced a series of experiments, the result of which was a cylinder flute with the simple and natural expedient ot reyulart y graduating the holes. Fig. 3 shows the our cylinder with its equal-sized holes; Fig. 4, the new one with regular gradations. It is true others hartdeclared that cylinder flutes with graduated holes, were made by them prior to the appearance of the "Clinton cylinder," and that the said hole, decreased regularly "always one quarter of a millimetre" (about l-105in.) "in diameter. Be this as it may, such a gradation would have no practical influence on tone or tune, even if it could be accurately marked ou the flute's round, A surface. It would bo beside the purpose to re commend any particular flute, but if we are ever to have what has been so patiently and industriously sought, I think we have got it in the Clinton Cylinder; nor are spectacles needed to show us that the natural laws of sound have not been violated; the old system of fingering is retained, and the long cramp F natural key discarded; there is also a means of taking this note with the first finger of the right hand, as on the Böhm; but this involves no alteration in the fingering ot the F sharp, or the old fingering of the former.

My task is done, and I have to acknowledge the care and accuracy with which my drawings have been reproduced; and I must, en pansant, express my admiration of the beautiful engravings of machinery, which are constantly given in this periodical. And now I bid adieu to the flautist-of the Enoush Mechanic with hearty good wishes both for themselves and our favourite. Although no longer able to use or enjoy it, I ha \ e the satisfaction of knowing they can do both. Finally, I entreat all to believe that I have kept steadily in mind the motto which heads Uie*t

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