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i« f :il and industrial arts. That your petitioners hare iavariably protested against the abolition of these laws, a» being suicidal and unjust to the nation, both as regards the protection of property in pntenw, and the mental acquirements of the honest inventor. That your petitioners sensibly impressed with those views, humbly request that your honourable Honse will confirm by law the following, recommendations, and rectify such other abuses as have been found detrimental to the working of the patent laws.

•* 1. That scientific assessors bo appointed to represent mechanical, chemical, and natural science, to assist the judges and law officers of the Crown in deciding patent cases, oppositions, and infringements, so as to render their decisions more oertain and in unison with each other, and thereby prevent litigation and uncertainty. '-'• That the said assessers be assisted by a competent staff of examiners to report on the novelty of all applications for letters patent, and thus prevent a number of patents being granted for the same invention. 3. That the present system of provisional specifications and six months' protection to be abolished, and in the place thereof a system of registration be adopted at a trifling cost, giving a mere extended time, say twelve months, or perfecting inventions before application is made for letters patent, and during the twelve months the inventor to have the power to amend hie registration if he finds it necessary. -1. That letters patent shall continue in force, by the payment of an annual tax, for 15 years from the date of the first registration. 5. That a fine be imposed upon any person selling or exposing for sale any article аз patented when it is not so, and that the date and number of the patent be affixed to all articles sold as patented where practicable; this would prevent many frauds being practised on the public 6. That a special judge be appointed for the trial of patent eases, and that on such trials the judge be assisted by the assessors, and all questions of fact, as well as o£ law, be decided by a judge without a jury. 7, That patents ought not to be granted to importers of foreign inventions. 8. That the granting of licenses shall be compulsory under the approval of the assessors. 9. That the bord Chancellor shall not be limited to one mouth only for sealing a patent after the proper time in cases of opposition, and aleo that he should have power to extend the time for the payment of subsequent taxes in cases of accident or extreme necessity.''

LETTERS TO THE EDITOR.

[We do not hold ourselves responsible for the opinions of our correspondents. The Editor respectfully requests that all communications should be drawn up as briefly as possible.]

•«• All communications should be addressed to the Editor of the Englisic Mechanic, 31, Tavistockstreet, Coveut Garden, W.6.

All «beques and Post Office Orders to be made payable to J. PASSMORE Kdm'ards.

I would have every one write what he knows, and as much as he knows, but no more; and thst not in this only, but in all other subjects: Kor such a person may have some particular knowledge and experience ef the nature of such a person or such a fountain, that, as to other things, knows no more than what everybody does, and yet to keep a clutter with this little pittance of his, will undertake to write the Whole body of physicks: a vice from whence great inconveniences derive their original. Montaigne'!

USEFUL AID SCIENTIFIC NOTES.

ARTIFICIAL PRODUCTION OF ICE IN INDIA,.—Dr. Janssen relates that, in many parts of the Indian Continent, tne natives dig shallow pits in such localities wuleh are quite freely open to the sky, and distant from trees, 'the pitshiré lined with straw, and upon the straw are placed disnea (made of a very porous eattaeawere) mied with water. During the -calm and dear uurhts prevailing durlug the period from Noveakber to the eud of February, the water placed in the dishes freezes, yielding n -olid cake of Ice, while the temperature of the air is + 10«. Dr. -Janssen has investi gated tills entions subject experimentally, and has found that the freezing is principally due to the radiation during the night; but the evaporation of the water, aided by the porosiiy of the earthenware employed, is not to be overlooked, at the 'time.

MACHINE FOR PEELING POTATOES.—The К с v. Lie vin Bou teen.— Tim author (Director of the Convent of St. Josepb-de-Notre-Dnme-de-la-Trappe, at Forges ( Halnnut, Belgium), has contrived a machine, bytlio aid of which one man can peel, without very hard work, from 259 to -150 kilos, of potatoes in a hour's time. After the tubers have been first roughly washed, they are placed in a cylinder pierced with holes in tuen a manner as to form a rasp ; the bottom of this eyllnder is made movable, and also pierced with boles, a» )u»t rased. Motion is Imparted to the bottom of the cylinder by suitable means; and, by this means, to» potatoes, by the friction against each other and the rasp», are rapidly peeled, while a jet of water is at the same time applied to wash the peelings down.

GOLD COINS—These were first issued In Franceby Clovts, ал>. 4<j9. About the same, time they were issued in Spain, by Amiibrir, the Gothic king, in both countries they were called trinities. They were first issued in England iu 1257, i>i the shape of a penny, of the value of 30d.; only two specimens have come down to us. Florins were next issued, in 1344, of the Value of es. The noble followed next, of the value of «3j sd. ; being stamped with a rose, it was called the rpse noble. Angels, of tlie same value as tho latter, were issued In 1465. The royal followed next, In НПО, of the value of los. Then camo the sovereign of 20s,. in 1489. The gold crown, of the value of 10»., followed in 1527. Unites and lions were issued iu 1603, aud exUTgat« in MM. The guinea was first issued In НИЗ, of Qnlneagold. In 1733, all the gold coins (except the guinea) were called in, and forbidden to circulate. The present sovereign was first issued in 1817. The American half-eagle was first issued in 1793.

DE OMNIBUS REBUS OiELESTIBUS-ET QUIBDSDAM ALUS.

Sir,—My knowledge of the views of Mr. Williams with reference to "the Fuel of the Snn " is wholly derived from the letter of "The Harmonious Blacksmith" on p. 180. Judging from the précis of the work there contained. I should say that it consisted of a little Laplace, a trifle of Mayer some Proctor, and a good deal of SIT William Thomson; the whole simmered together and (as tbo Cookory books say) "served up hot" with Williams.

It Is extremely hard to pronounce any opinion upon an hypothesis—or rather upon hypotheses—coming before one in such a form ; but certainly a difficulty or two suggests itself to my mind In perusing tho abstract of Mr. W.'s book which "The Harmonius Blacksmith" has made. Aud firstly, it is perfectly easy to conceive that the attractive power of tho Sun should cause the descent on to bis surface of any amount of cosmlcal matter (call such matter planetoids, aerolites, or what you will) which comes within tho sphere of such attraction. Tho mass of the body or bodies so attracted, being assumed or known, and their velocity on reaching the Sun's surface, also determined, the amount of heat generated by their impact becomes amatler of relatively simple calsulntlon. Woll, but then, how does the Sun '-leave behind him," what is termed in Mr. W.'s book.his "Exhaustedfuel?" Coufining ourselves to ono single fragment of this elle to matter, say a globe of it 1ft in diameter, can we ooncoive any force which Is capable of projecting It vertically from tho surface of the Sun (whose mass 1b, bear In mind,some 317,000 times that of the Earth) to a sufficient height to place it sensibly beyond his at tractive powci? Were each globe shot off tangentially, one of two things must happen, dependent upon the rati» between the forco of propulsion and that of gravitation. Either our assumed particle would describe a parabola, and fall on to the Sun's Surface again ; or, if It were projected with sufficient velocity to carry it once round the globe of the Sun, it would

foon describing that orbit ad infinitum—or until some rcsb force camo into operation to deflect It from It. At all events it would become permanently attached to the Sun, cither as a part of his own Globe, or as a body circulating round him. This is my difficulty about the "leaving behind" hypothesis. Then, again, I confess, that, in common with "The Harmonious Blacksmith," I utterly fail to see why the Sun should be held to be the parent of the Asteroids, and only, soto speak, the father-in-law of the other members of the svstom of which ho is the great centre. (Here we lo'e the flavour of Laplaco. and detect a very pronounced one of Williams.) Nay, I go farther than your correspondent; and would ask,why, if we assume the various planets to Déportions of tho primal matter of our system; and, to use a very homely simile, flirted olí the Sun during his original process of condensation from nebulous matter, like water off a mop; why, I say, may we not credit the various planets with the production of their respective satellites In the same way? There is certainly nothing in observed appearances to militate against this idea.

Then again the invitation to believe in the existence of" aqueous vapour, Ac," in "Interplanetary spaco" scorns to make an extrnordinarydemand on our credulity. Certainly its tensiou cannot be very great with a temperature according to Hopkins of—37°'S Fahrenheit, and of Fourier of—59" Fahrenheit! It Is, however, a little idle to argue on a large proportion of such assertions as Mr. Williams's books appears to contain, for the simple reason that they are neither susceptible of proof nor disproof. И a man were to tell me that the inhabitants of Mars had nothing to read but " Tapper's Proverbial Philosophy, " 1 could not ooutradlct Lim. I could obviously only answer that, if so, I pilled them from the bottom of my heart.

I am rather afraid that liiere is no single work containing the information asked for by Mr. D. Jenkins (2659) p. 106, in an available form. Denison's capital book. " Astronomy without Mathematics," lins a table of tbo data Mr. J. requires: but this doesnot include the elcmeuts of tho individual asteroids. It is u 4s. book published by the Christiau Knowledge Society. "I.oomls's Treatise on Astronomy," another most interesting book, published (at, I think, about ,ss.) by Harper Brothers, of New York, contains soinewbatcxtensive tables of the elements o( Solar system, including ninety of the planetoids; but, wherever quantities are given is milei, they are calculated on the old, and certainly erroneous, Solar parallax of of S'-.уч. It tins, bv-the-bye, just struck me as possible that Mr. J. Normán Liickver's " Elementary Lessons in Astronomy," price5s. Cd., Mncmillan and Co.. will be found to have what your correspondent wants, in it; but as 1 do not possess the book itself, I cannot assert positively that it does so,

I need only refer " it. 1'. D.."(p. ISft), to p.lM). I muy tell"" Secundum Nntuniin." that on the 2»tli ofjMuy, Saturn is on the N. W. boundary of Sagittarius;

aud Mara in Aries. Urenns Is still In Gemini, but will move into the confines of Cancer toward* the Autumn.

With regard to the queries of " H. A C." (p. 1901. I do not believe that anyone has yet picked up D'Arrest's Comet; or, at all events, has made any announcement of having done so. /fit be visible, it is the only one, great or small, in the night sky at this present writing. In the Supplement to the" Nautical Almanac" will be fonnd Ephemerldes of Ceres, Pallas, Juuo, Vesta and Astrsea for every tenth day during the year ; and during certain months for every second day at Transit. Your correspondent's query as to the apparent diameter of the various members of the Solarsystem in inches, is a really senseless one. Accepting, however, with the ordiuary works on Optics, loin, as tho standard of distinct vision, all ho has to do Is to take out the tangents of the angular diameters from a table of Natural Tangents, and multiply these by 10. For example, suppose the Sun's apparent diameter to be 32', what is Its apparent size in inches? Turning to onr tabic we find the Natural tangent of 32' to be -00930*?, of the radius, whatever that may be, and multiplying this by 10, we shall at once obtain this result, that the Sun Is apparently 093in. in diameter. So that If we cut outa little disc of paper o-Hii; In diameter, and place it loin, from the eye It will just cover the Sun. Venus at present, measured In the same way. will appear only •00007in. across; and so on. All this, nevertheless, as I pointed out in anewerlng a cognate question some two or three weeks ago. has little or no meaning, but it is the only reply of which " H. A. C's" demand is susceptible.

"Salopian " (3749), same page, appears to be a little vague in his notions as to the centrifugal tendency of bodies on the Earth's surface. The centrifugal "force" (as it is called) varies as the square of the velocity of the body, and In the Inverse ratio of the distance from tho centre. At the earth's equator this Is by no means an inappreciable quantity ; us a very little reflection will show that while a man standing on one of the Earth's poles bad merely turned one« round, another on the equator will have flown through some 25,000 miles. As every particle at the equator, then, is travelling round at tho rate of more than 1000 miles au hour, this effect becomes very appreciable; In fact a body transferred from the

polo to the equator loses something like

part of its weight from this cause alone. If we assume the Earth.Jthcu, to linvo been in a plastic state it is easy to вое how It would be, so to speak, squeezed out where tho pressure was least. Were tbo rotation of our globe to increase about seventeen fold, everything merely resting on its surface at the equator, would fly off. A Fellow Of The Rotal Astro.vomical Societt.

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THE TELESCOPE.

Sir,—It happened that some time Blnco, two different friends whom I recommended to go to Slater, of 136, Eus ton-road, London, each complained to me that he could get nothing whatever done by that optician; and that ho had written and wailed, waited and written for what he had ordered, ineffectually, and in vain. Speaking, then, of Slater, on p. 130, I applied the epithet "dilatory" to him. I have just lcarued from ono of the gentlemeu referred to, that he now tiiuls out that Slater was seriously ill at the time of which I have spoken. This being the case, I feel that I was scarcely justified in using tho word I did, to describe a man wiio was, as 1: now seems, sick, and physically incapacitated at the time from doing auy work ; Ithe more especially as I never saw Slater iu my life, nor have ever had any communication, oral or literal, with him. Without, then, waiting for any disclaimer on his part, I will ask my querist, Mr.Bsgulcy, to erase the words " were he a little less dilatory," as applied to Slater, and to read the sentence in which they occur straight on without them.

"Ignoramus 2" (2668>, p. 160, can have an object glass of longer focus, and consequently higher^niaguifying powers adapted to his present telescope; but this will Involve a corresponding lengthening of tho tube. "The other glasses in the inside" form the eyepiece, and could be used with any object glass.

As "Neptune" gave no data whatever for the computation of the curves of his object glass, save the focus of his crown lens, and that of the whole combination, I regarded Mr. Vivian's reply as an absurd one ; aud ( believing that, like many other people, ho thought that he had nothing to do but to take out the quantities by inspection from Herschel's table) attempted, not very dexterously I must admit, to "chaff" him. I see, however, by his letter ou p. Ш, that he really does know something of the subject, and must express my regret for having done so. If Sir. Vivian after this admission will condescend to take my advico. though, I would commend Coddington's formule to him in preference to Herschel's, as being, i think, more manageable Mr. V. is probably familiar with the " Treatiseon tho Reflection and Refraction of Light." It was published at Cambridge some forty years ago. 1 am u little amused at your corrcspondcut's idea that becuuse a man, of necessity, has a good many " rather longoompntatious "to make, it is only reasonable to oxpeotbim voluntarily to undertake more.

I may just tell Mr. Bagulcy, p. 185, that bis resolution of y Virgin» with the power ho spécules does not prove much one way or another.

Mr. S. T. Preston, p. 185, apparently proceeds on the assumption that all opera glasses give a power of two diameters only; an assertion to which (with л

glass magnifying four diameters now before me> I emur. Of course, in the Galilean telescope, the distance between the glasses is the difference of tLeir focal lengths, aud the magnifying power is obviously the ratio of these focal lengths: so that the focus of the eye glass enters as an element into the calculation. The shorter such focus Is. the farther from the object glass will the lens be placed, aud the narrower consequently that part of tilo cone of rays from the objective which it intercepts, Nevertheless, your oorrepoudent is perfectly correct iu his assertion that their le a practically useful limit, very soon reached, to the aperture of the Galilean form of instrument.

At the reqaeet of Mr. К G. Anderron (3712), p. \Ю, I have turned back to tho volume ami page of nur magazine which he specifies, and can only say that ble method appears to me to be capable of affording resulte at least M correct as those obtained by the method of measuring courses of bricks, &c. and that where, as in his first case, an image of the whole solar disc could be made to coincide accuiately with a circle of known diameter, ata carefully determined distance from the place where the rays from the object glass cross, I should expect to obtain a very good determination. In his second more complicated caso, I should not be quite so hopeful of the ultimate practical result.

Myself a mere Amateur, I should prefer that some working optician should answer "Dioptrics" (3713),

1). 189, but I may just say that I never in my life irard of grinding a Ions on a (/ioas tool. In the case of my sole attempt In object telase making. 1 first computed the curves, aad then made my own ftratt tools in the lathe. These latter were about ball au inch greater in diameter than my intended It*us. I do not think that iron would comcup to a sufficiently flue surface. I can get quítela semi-polish on a lens by tbe nid of fine flour emery alone, and the brass tool itself, nod when It has arrived at this stage it may be transferred straight to the polisher. I was once told, asa great favour, that Alpaca was the best material to construct the polisher of. Putty powder and rouge are tfho polishing materials.

I may tell "H. A.C." (3571), p. 190, that I rather question the power of anSoln. reflector to divide a' Bootls at all just now, if Secchi's last measures of it are to be trusted ; but that, as soon as the distance of the components exceeds 0"5, any power over tiOO ought to divorce them. I must add that I have not looked at this star fora long time with any instrument which has a gh»st of a chance of separating, or even elongating It, and that therefore my leply Is a purely tbeorctlenl one. A Fellow or The Royal Astronomical BoctxTT.

COTTON SPINNING.

Sir,—Your correspondent, E. Halmsbaw, page IBS, asks a very reasonable question, when, in reoly to •* B. W, R.," he asks the object of some jack fmmes l>etn# made for the bobbin to lead, aud others for the flyer to lead, if it is immaterial. The result of the bobbin leading has not any effect on the threat!, as K. llalmsley supposes. Having frames of both kinds, 1 wilt just state my experience with them, and ray brother Cottoniaus cau draw their own conclusions. The advantage arising from the bobbin leading, can soon be proved as follows. Break down an end from

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two frames, ono of each kind, and let the frames continuo running, and you will fiud the frame where the flyer leads, making the roving iuto waste, whereas the frame where the bobbins lead, will not make any waste at all; to those that have not the means tu try this practical test, the enclosed sketch wilt explain all that is required. So much for the advantage. Oí course there may be more, aud perhaps even greater advantages than this, hut il there Is, unprejudiced trials and close observance, have failed to make them к nown to me. Now for the rfwadvantages. let. You can drive your frame at a greater speed when the flyer lead.". If there Is any doubt about it, let anyone try to start a frame with the bobbins leading, and the spindles runniug 900 per minute, '¿nú. It is evident that to ruu any part of a machine faster than íh required, and only get the same weight made thai you would if you run it slower, is a disadvantage. Extra wear, tear, power, and oil, are the result«. ■ i п. The " tenter " has to use ber left hand in piecing the ends up. This is the sum and substance of my experience—I prefer the "horse before the cart," or the flyers to lead. Can any of your correspondents furnish mo with a recipe for making size for the bottom of cope? I have tried several different mixtures, but I cannot get anything to act to my fancy. I shall be glad to receive any reply.

Hakmonious Cotton Spinner.

Sir,—I am greatly obliged to E. Slater for his explanation of the weights used in cotton spinning. I have been very much puzzled with a roving table, in Alexr.niler Kennedy's "Cotton Spinner," second edition, page 118, and by it I bave oeen misled. 1 ulsp feel obliged forth« very good explanation of the cone, and the sun and planet motion. I am sure your paper must circulate in Lancashire, If you can get such correspondents to continue their labours. I am very anxious to uuderstand tho baking off motion of a nelf-acting mule, and also the operation of the cam «haft. 1 find when the carriage is at full stretch, the rim pulley reverses about a quarter round, but I eauuot find the moving power or connection with the drlviug pulley. Will tome one explain them?

Edwakd Iiaberghax.

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STEAM BOILER FEEDING.

Sir,—As a conciliate betweeu me aud several of my brother readers respecting a system of ieeding steam boilers without the use of pumps, &c, illustrated on page 5^6. No. 25+, Vol. 10, I beg that you will kindly afford a little of your valuable space to describe a system whfch I bave gone to the pains and expense of proving, that a boiler may feed itself out of a well or tank even 10ft. deep, by simply shutting and opening one cock, instead of ut.ing regularly four for the purpose of ieeding one boiler, as previously described by me, and six as described by Messrs. slum-l and Mason; and that one cock Is simply a fin. steam-cock. A shows the end of a 20-horsc holler. Ml. in diameter. В shows the feeding vessel or bottle, set on the boiler wall, ¡«mi shaped at each end as seen, well made; nad С С is the fire-front, made of the same pla'e iron as the boiler Into a water case around the door entrance r, Oln. wide inside. The vessel В is 2ft. 91n. diameter, and 5ft, Oin. high, s s is the ¿In. steam pipe, with cock at F, which pipe enters the top of the vessel, с с о is the suction pipe from the bottom of the well or tank into the top of the vessel. lHn. size inside, with valve orctack,'box atE, In which is flxedjon the pipe a abrasBbacked leather clack, «n Is an inch rape from thr bottom of the vessel iuto the bottom of the case С С aud W is an inch pipe from the case the other side of the doorway into a low part of the boiler, with a safety cock W. d d is an inch branch pipe from the pipe h into the cistern O, and the pipe /t with cock II is аЦ1п pipe from the bottom of the cistern Into a low part of the vessel, and continued inside in a spira! form Up wards and out at the top, and agnin joining into the cistern bottom st M, which cistern must, bo larg'1 enough to hold sufficient to fill the boil*r for starting The boiler, in the first place, after being fixed ami tilled bv some means, the steam being got up. the vessel is blown full by opening the cock F, which is then shut. The steam, on coudeasiatr. sucks water up tin pipe a until by the pipe с it reaches the vessel. Then immediate condensation tak**s place and rapidly ни-к up the water, which, when spent, the pipes яг keep full by the clack E. The steam having been put on again, the water In the vessel raises the valve V and passes into case С С, where jt is healed before entering the boiler by the pipe W. iThe cock atW is only tobi used should the valve V fail.) YYhcu the vessel ii empty, the steam will cause a rumbiiug noise iu the heating case. Then shut oil the steam. Having raised water Into the cistern О by opening the cock D, when forcing the wat'T out of the vessel, the condensation of the high pressure steam may be facilitated by opening the cock II aud letting the cold water travel Ihrouuh the spiral pipe itt the vessel, the heated rising Uito the cistern at M. which cock must be shut before putting on the steam. Thus tbe water is raised aud forced into the cistern О or boiler A, before eutcrlug which It Is heated.

John C. Shewan, Pitchcombe Works, near Stroud, Gloucestershire.

TELESCOPE CONSTKUCTION.

Sir,—Many letters appear in your columns on the above subject, but they deal mainly with the mode of working the lenses into form, and mounting them. Will anv of your learned contributors tell me If there is any theoretical objection to a telescope made thus:

arc merely types of a elaaawhlch wilt always exist. Suppose 'Parallax* <!<>••• unsettle the minds of many people who-. have not studied the subjsf^s*} what thtn? It serve* them right for leaving the subject unstudied." I think the closing, part of this statement ought tohave been qualified. It doubtless. does servo those persons right who have had opportunities of acqulrlug the kind of knowledge in question, and have neglected то do so. But Mr. Proctor muKt be a very young man not to know that there are thousands whohave not had such means at their disposal, but who are veryanxious to be set right, not only upon the subject of astronomy, but upoa other department« of knowledge; aud to do so 1«, I conceive, a duty incumbent upon all those who have time and ability. While I should be onet>f the first to denounce captious* objectlons and frivolous questions, it would give me pleasureto hear, and. were 1 able, to answer the objections of tbe inquirer upon any subject. If it be desirable to enlighten mon> minds upon thcconstftutlonof the universe by books and lecturee. ь surely cannot be thought unnecessary to meet the objector, or remove the doubt« ot the wavering. And for what purpose did Mr. P. write those admirable papers on "The Earth, luv Figure and Motions," published iu the Knm.ish Mechanic, but to upset the notions of "Parallax "and Co., and to settle the minds of those whom thatgentleman bad unsettled? In reading those paper*, one could scarcely draw any other conclusion, especially a» Mr. P. mentions meb persons several times therein. J. Dvek, Brunswick House, Tanner's Hill, New Cross.

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Newtonian of tiin. aperture. The air was somewhat" unsteady, but the stars were exquisitely brilliant, a» the ruin had wa*hed all the soot out of the atmosphere. After examining several objects, we turned the instrument on Urste Majori«, and made independent sketches of the minute stars between Mizarand Alcor. The sketches were then compared, and the accompanying drawing represents the result ob our work. It will be observed that several minute stars, not seen by u F.R.A.S.," are shown in this drawlog, also that some given bv him are omitted. I donot pretend to explain this except by supposing that we devoted our attention more especially to the right. side of the field. The powers used were V0 and 200, It we had been able to compare our sketchoi with that by M F.R. A.S." at the time, I have no doubt that the~ puissions would have been supplied. Arthur W. Blacklock, 3„\ Old Stcyue, Brighton*. P.S.—In reply to Jamte Gray. p. НИ. I am unable to tell him whether glass disc«, suitable for specula, can. be obtained lu Aberdeeu; I do not think they can». but should think that Glasgow was a muck more likely place. I will scud a description of the method I have adopted for supporting my speculum, but I am not quite satisfied with it at present. As soon as I can get to work with it again, In June or July, I hope to improve it.

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May 20, 1870.J

bv twin* high charges of quick-burning nLder and proportfonably increasing the. SreWltn of guns, rather than by a more- gr.dual evolution of the force which Impel* the shot.

Aucient artillerists employed slow-burning

nowdei-something like ourrocket composition.

and when they w.mcd toli crease the range

They liSded to the length of the gun, so that a

lmrier onautity of their powder might be

DarrfedlSdnconyverted into gas before &*«

«i« exaelled from its chase. The r-eypuau

bronze Piece, at the Horse Guards, and Queen

EU°»heth's Pocket l'istol, at Dover are ex

imo'esof the carrying out of this Idea, audi

doubt not that what in those times were con

lid" red lone ranges were obtained for they

did the right Thing, inasmuch as the pressure

of the gases-evolved must have gone on in

crwsinsT untiltbe shot had .ravelled a long way

toward* tK muzzle, even if it did not lncreuo

nntil the shot arrived there.

Modern artillerisu have donemst the contrary thing. Instead of adding to the e«K*whfch makes guns extremely unwieldy and inconvenient to load at the uiuzzlc-they added to thc"r thickness, especially at the breach, and employed powder which burned so rap dly tS? the shoPt was expelled with the required velocity Irom a short, heavy gun. So far as re-ards mere range, one system seems as good a?luc.other arid although 1 have classed as modern tht-'short, thick Cuns-whose binder parts are.imllarly proportioned to those of ho heavy-^cTM^ Christians, which the old dWine wrote what ho termed a there to expedite the progre* toward, futu.e bliss-this musthe taken rum grano talis, for the bronze gun at Bbuftpore is almost as well proportioned a* a modern brass field piece, and as at specimen of ornamental founder's art it would bo difficult to surpass it, although the euttog t« lar from sound. Its length is »fc lameter at breach, 3ft. 3in.-bec Robert Mallet t work " On the Construction of Artillcr).

1'robabiy modern artillerists have carried the reinforcement of (he breach to its greatest us. ful extont, and the Dahlgren guns in lb-American service, which resemble IMma water bottles in form, are perhaps the strongest cast iron guns yet made, but, as every engineer well knows, there is a practical limit to the additional strength which can be obtained by mero addition to the mass of a gun, for when the diameter is very gTeat. the interior cools so slowly tha there:i.considerable danger of tho material giving way under comparatively slight strains, from tie fact that the irregular shrinkage tends to separate the inner from the outer parts. Hence the advantage of building up guns in successive layers; aud this also enables us to employ tough wrought instead of brittle cast iron.

The repeated failures of heavy cast iron guns Induced a 'cute Yankee to revert to the principle of gradual evolution of force, which he carried out by making lateral powder chambers communicating with the chase of the gun. These lateral chambers were charged with powder, and each charge was successively Ignited (after the projectile had passed it) on its way towards the muzzle. This is employing many charges of quick-burning powder to do the same work that one large charge of slowburning powder does equally well without the iueonvenience nnd loss of itrength which must result from making and loading luMiiy powder chambers. Like slow-burning powder, it prevents the gun from being subjected to sudden destructive strains, but the invention certainly ttoet not resemble its inventor in being simple.

Gunpowder being only a mechanical mixture, aud unlike gun eottou, aud most other explosive substances, a chemical compound, it is not subject to the law of definite proportions in other words, we can use anyfproportion of; its ingredients we lind most suitable for the especial work we waut it to do. In addition to the command this fact gives us over the rate of ice combustion, we cun further modify that rate by varying the size and form of its grains. When reduced to dust it cannot be made to explode at all unless the mass bo sufficiently heated for ignition throughout; lighted at the surface it only fizzes, as every schoolboy kuow*. As we increase the size of its particles, so do we alford more room for flame to be propagated between them, and the more rapidly is the mass burned and converted into gas, which is only saying, in other words, it explodes, for explosion differB from combustion only in the rapidity with which its products are evolved ; but this must be taken cum yrano, for it is obvious that if instead of being made Into grains it were in one mass, it could only burn at its surface, and would bo very slow burning stulf—we can hardly call such masses powder.

As usual, success Is only to be achieved by compromise, and the practical problem is, to find the pioper size of the grains so that they shall burn rapidly enough to induce a eotuttititly-incrtasing pressure in the chase of the gun, while the 6hot travels along it without causing a vrry sudden and intense pressure before the lDertla of the shot is overcome and its motion commenced. When we can make gunpowder which will aot only begin to more the shot slowly, but also communicate a sufficiently accelerated velocity to it during its progress towards the muzzle of the gun to expel It at the required velocity, the problem of long ranges from light guns will be solved. >rom the report ol some late experiments at Shoeburyne*8 on different klnusof powder. It is evident that that problem, if not yet quite solved, is sear lta solution.

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The range of a projectile, creleris paribus, depends on the velocity with which it leave» the (fun, and when the force which impels it is gradual!) increased during its progrese along the chase, it would appear that it» greatest Telocity—i.e. that with which it quits the gun, may be greatly increased beyond anything which can safely be obtained when, as usual, tbe pressure of the gaees is greatest before tbe shot has travelled halfway along the chase, lu the latter case, that pressure acts on the shot much as a bow acts on an arro w—i.«. it drives it with the greatest force at llrst, and with a constantly diminishing force until it ceases to out; It facts the projectile instead of impelling it with Increasing velocity; but whether it makes the gun kick also Is doubtful. Probably the total recoil, if less sudden, would be rather greater iu amount if the force be evolved gradually, and continually increases in intensity, for, from the same causes which will give a longer rangeforward to the projectile, we may expect a somewhat longer rango backward of the gun-¿.г., increased recoil—for the Inertia of Its muss would be more gradually Overcome, and the force which causes it to recoil continually increase during the passage of the shot along the chase.

When solid steel guns were first Introduced, our <iuiclt-burnlng powder almost invariably burst them unless made very massive at tbe broach ; in fact, the evolution of force was so sudden that the surface of the powder chamber was burst from within; the material was disrupted before the strain could be communicated to the outer portions of It, and, for capability of resistance, tho outer parts might as well have been absent It was this •• busting up," as the Yankees call it, which Induced the Prussian artillerists to decline trying Krupps solid steel guns with English L.G.R. powder, for they, being reasonable men, ouly wanted to expel the ehot with sufficient velocity, and did not want to burst their guns. They did not see tho economy of the British custom of making very costly guns and then subjecting tbem to strains not required for any practical purpose, so, instead of English L GR.. they used their own prismatte powder, which sent the shot quite as far without "busting" the gun. So longa« the required range la obtained, what more do you waet? Surely, even those destructive English artillerists ought to be contented with this I

After a reasonable—perhaps I ought to write unreasonable—time had been taken for consideration, our sapient authorities seom to have found out that it is desirable to avoid destroying wantonly our very expensive wrought iron and bronze guns by subjecting them to needless strains, which don't increase the range of the shet, but which Jo, sooner or later, burst the gun; so at last they have followed the Prussian example of making prismatic powder, whose grains are somewhere about the proper size 10 burn at the required rate, and having provided the means of ascertaining (approximately) the pressure of the gases in the chase at the intervals of the shots successively passing certain portions of its length, they found the strain on the gun was reduced from 4-500 atmospheres when L.G.R. powder was used to 15 atmospheres when prismatic powder was employed. Weed I add that by the employment of the latter, not only will the "life "of our guns be prolonged, but that It is very probable the multitude of east iron gune in store may—especially if they be treated a la Palllser—be rendered available for the extremely Christian work of killing tho Queou's enemies without much danger to those of her subjects who may hare the blessed privilege of doing that work of necessity, if not of mercy, when the occasion wnrrants that work to be done. May that occasion be far distant, or rather. Heaven fbrfeud its occurrence! Tub Hahmoniols Blacksmith.

MESMERI9M.-REQUEST TO " SIGMA." Sib,—I much doubt if among all mv fellow correspondents In our journal there Is another who wrlteB in a more truly philosophical spirit than "8igmn," and had I not before been acquainted with tho facts which are commonly termed mesmerism, to which he bears testimony in lío. 257, I do think his testimony would have compelled my credeuce, for all his communications exhibit plenty of Internal evidence that his mind is not one likely to be deceived into belief on insufficient evidence, and that he would wilfully deceive othersSI deem quite out of the question.

Improbability means little else than unexpectedness. To me, the facts he avouches seem no more wonderful than any other facts with which wo are familiar. Wonder is but the usual expression of ignorance when the unexpected transpires, and Improbability seldom means anything more than the incongruity of the unexpected with our very limited knowledge; strictly speaking, we can hardly be justified ш saying that any alleged new faet Is improbable, however little we may expect its discovery; In fact, this allegation of improbability is only the old fallacy of making our ignorance a measure of the probability of what we don't know, and I am sorry to add that from the reproach of doing this I cannot entirely acquit "F.R.A.S.," who-on thé subject of mesmerism only—seems to assume that what he is not convinced •of, must be at least improbable. If not absolutely false. See his communication in a recent number.

•Having had but little personal experience of the higher phenomena of clairvoyance, 1 should, I trust, in common with many of my fellow reader», who are earnest seekers of truth, be very glad to be further enlightened concerning those phenomena ; may 1 therefore, in their behalf, as well as mine, request" Sigma" to inform us what Instances of the perception of things and occurrences at distances far beyond visual ken, and notwithstanding the interposition of opaque substances, he has witnessed. "Sigma" wlllof course understand 1 alludo to such phenomena as the perception of the fire raging at SMckholm, by Emmanuel Swedenborg, when he was dining iu Berlin; or the celebrated ease of the young girl, whose name I forget, who accurately descnLed the furniture and contents of a room many miles disinnt from her. which she had never eeen by ordinary vision, or indeed knew the existence of, until placed en rapport. I greatly Гонг pomo of tbe intellectual descendants of unbelieving St. Thomas «ill bo tempted to cast ridicule ou me fur asking for such information iu

serious soberness. The minds of these not very philosophical sceptics, who assume they know all Nature's possibilities, seem to tho unlearned Blacksmith. In relation to this subject, to be very like those of the blind aud deaf In relation to the phenomenn of light, colour, and sound. The said Blacksmith supposes he must "grin and bear it;" in fact, ho is used to it. Having been blessed by Providence with a rather bro:ul back, and being, as regards ridicule, a pachyderm, he can well afford the sneerers should have their enjoyment—llko Dickens' good natured coalЬеатвт, whose wife "aopptd"— "it pleases she and don't hart I." and If my queries elicit useiul Information, their purpose will be fulfilled, however much ridicule the questioner may he called on to bear; moreover. If it will afford nny additional gratification to the sneerers, I am willing to admit that my mind is so shallow that to me our ordinary vision and other perceptions, arc quite as wonderful as any of the alleged wonders of clairvoyance, and, that I believe we don't wonder at vision, hearing and feeling, ouly because we have been familiar with them from childhood- The Habmomols Blacksmith.

Wnr I DESIRE TWO RANKS OK MANUAL KEYS TO MT HARMONIUM—REPLY TO "ELEVE."

Sin,—" Eleve " asks why should Ц rows of reeds get two rows of keys, when one row minht do the work? Now, however crotehetty I may be—and, like all hardened sinners, I glory in mine inlquitv—I am "free to confess " that I don't kuow why the aforesaid »A rows of reeds should get two ranks If one row can be made to do the work; but that It ran is just the thin" I have not yet been shown. I should like to be.

That there may be no possible misunderstanding, I will specify the »or* I want my harmonium to be capable of doing. N.B.—It Is, when properly done, really icork, although usually designated by the term playing. Tho work wanted is to play a melody with true vocal expresrion (whether that expression be obtained by the asnal mesns or i la m ni«, which I greatly prefer), and the accompanying ef that melody by the sounds of other reeds, without the possibility of those sounds being stvelltd to any objeeelonableextent. I also reauire that in the performance of the said accompaniment I shall not be limited to F first space, or any other note within the compass of my harmonium, for the sound of highest pitch wlth|whteh i may faucy to accompany the said song or melody.

In this I require no more than every organist can do. if he plays his melody on the swell organ, and accompauie.i it on one of the other organs whose keys are beneath his fingers. If " Eleve " can show me how to do this on an harmonium with only one manual rank, that matter-of-fact character and rtmnrkable economy in tbe matter of & s. it. —however liberal I may be of words—for which he gives me credit (I only wish I deserved it) will compel mo to admit thesecond manual rank to be quite superfluous; but until be does this I can no more wrrk or play without my second rank of manual keys than I can without that third rank of keys yclept pedals.

It is a great consolation to me to And " Eleve " supports my Immune (suggested) treatment of reeds, babies, and paupers, but I fear he is hardly prepared to g" what our American cousins term "the intlre animal." Some reeds, like some babies, squall so horribly, that I fear they must, like the niggers, come otan Inferior race, utterly incapable of civilisation. I am quite hopeless that either these cantankerous reeds or those yet more cantankerous babies ever can be educated by any amount of scentlHo "treatment" to utter agreeable sounds. The sooner such "veesele of wrath" are Improved off tho face of the earth the better for us all; and in mercy toour weaker brethren, or rather those brethren whose cars are weak and cannot bear "rook and strident tones," both reeds-and babies ought to be smothered intirely, as tho "finest pumntry" express it. Were some ol the pipes of our old city orgaus snrved that same, it would be no great loss to the musical world; but perhaps, like certain other utterers of evil, it is best they should go to the hot place, for then they might be '■' purified by Ore," and their material be converted into virtuous pipes, which might, if well voiced, utter angelic sounds. But, after all, it is best not to be too sanguine: aud blessed is he who expeototh nothing, for verily Ae shall not be disappointed. The llAintoMot s Blacksmith.

P.S.-Perhaps "Eleve" may say that if the expression ba ala main, which, by the way, most modern harmonium -пакете seem very shy of attempting, I could swell the melody and refrain from swelling tho accompaniment—I don't feel »juttecertaU ; "swelling," however common as я noun substantive, is a correct English verb; but n» matter, I shall be understood— true; but then I am precluded from accompanying with tones ol different quality or timbre, unless I limit the acoompauiment;to the highest note in the bass halfrank—say I'', or wherever the ranks of reeds are divided. So "Elevo" will seo that my favourite crotchet of expression a la main, such as I obtain in the celestina, terpodlnn, ouphenon, or sostlnente pianoforte, will not iulfiliny requtreiueut.

COMMERCE AND TRADE.

Sib,—Under the above title—which, by the way, is very much like two names for one thing—" Saul Rymea" says we are exporting less, and Importing more, than formerly, and he asks what kind of prosperity this indicates. I hasten to assure him that he may be " quite easy in his mind," notwilhstandiug the above le a true statement of declarer! values, and may he temporarily true at real values. That it cannot continué long is obvious, because howevor good .John Hull's oredlt may be, the foreigner won't trust him rid libitum, but the grent probability is, that the declared value oí our imports Is above, and that of our exports less than their real values.

If our imports are of greater intrinsic value than our exports, it is obvious we must be running into debt, aud we shall have to export more to balance the account. The foreigner will no moro trust John Bull without limit, than that first cousin of the ornithoryuchus, our tailor,—Puuch defined him, llko the

Australian animal, to be a brent with а Ш1. Like Sai torius, the foreignor will, somier or later, demand payment, and just as I should be compelled to "export" some medium of exchange—sav sovereigns or bank notes—from my pocket, or the balance at mv banker's, and deliver It into tho pocket of the ornithorynchus—I mean the tailor—iu satisfaction of" claim in his "little bill," so must we, sooner or. export some kind of wealth to satisfy the forefl claim for the balance due to him irom oarexci'Si imports over exports.

This balance may be paid in a great variety of W»ts7 Thus, it may be a direct remittance of goods of British manufacture, or of coal raised in Britain, to the foreign merchant to whom the balance is dua It may also be lu the form of tho precious mewls not raised in Britain, but purchased with the product« of British industry—for, be it remembered, gold and silver are as certainly, and only can be. purchased, by exchanging British manufactures for them, as French, Portuguese, and Spanish wines, American cotton, Chinese tea, or colonial sugar, are so purchased. Direct trade may be easier to comprehend by those who have not studied this subject, but it Is not necessarily more profitable than Indirect trade, and, whether we buy tea with silver, previously purchased in Mexico with British manufactured produce, or with calicoes In Canton, it makes nonessential difference ;is both coses they are ultimately paid for by British produce, exchanged for the foreign produce, and I nay add. that just as the export of silver is a positiw good to Mexico, which has more silver and less coitos» and hardware than her population requires, so a the export of silver from England to China a pose*» good, both to the Chinese And to us. They havt? <t\ to spare, which we want; we have got more я11я than we require from Mexico. The Chinese fonts they want more silver thau they have, so we induljt their argentiferous fancy, and obtain in exchange "the cup which cheers but don't inebriate." Verily we have our reward.

From the above it will be seen, that no so-called adverse " balance of trade " can continue long to affect us injuriously. Silver and geld are, commercially speaking, mere comvuxlitiei, and as properly the subjects of trade as the food and clothing of those who obtaiu them by mining. No doubt there are some political considerations Involved, to which I, who have treated this subject from a purely commercial standpoint, and assumed tbe continuance of pure on earth and good wilt to mankind, havo not adverted. Perhaps the latter is rather too much to assume vet. for we have not quite arrived nt tbe Millennium. War disturbs commercial exchanges, and when we have to

К revision an army in the enemy's country, we can ardly expect Its native hostile population to accept bank notes or bills on our government, in payment for supplies. In this case, of course, only the precious metals will be accepted, and those, unless In the form of coin current In the country, only as so much bullion, for It is obvious that the possession oi British coin, or its paper representative, would be prrmn foco evidence of treasonable correspondence with the invading army, and war makes short work of treason.

From these considerations, it follows that we must have a store of gold and silver, just as we require a store of gunpowder, they, lito it, being munitions of war. Whether these especial metallic munitions are best kept ready for warlike service by being coiued. allowed to circulate as a medium of exchange—te., as money, and become depreciated. Is quit* another question. As paper, which eatiaot become depreciated. Is а yet more convenient medium of exchange thon either gold or silver, and, as I have long ago shown, that the only condition required to prevent that depreciation, is convertibility into anything the holder prefers to bis paper money. I think it may be assumed that instead of etamplng the Image and superscription of the reigning Ciesor, orsovereign, on gold, and then allowing it to bo wasted by use aud loss, that I am justified in believing it would be more economical to store the gold and circulate the paper. But I refrain from boring my fellow readers with my somewhat peculiar notions on the currency question.

Why men should understate tbe real value of exported goods is a mystery, perhaps its eolutlon may, in some lnstauces, be found in the fact that some unenlightened foreign governments levy cut valorem, duties on the Importation of British manufactures. If these are passed at their declared, instead of their real values, of course they reach the native trader cheaper, but It has been suggested that although this may partly account for the différent apparent valuo of our exports and Imports. It is to a considerable extent compensated for by the common praotice of declaring tho value ol exports greatly iu excess of its real amount, which is said to be frequently doee by that race of 'arte merchants who insure ship and cargo at three times their value, in the hope they may never arrive at; the port to which it is pretended they are consigned. I am told this little game pay» very well when you are not round out, in which case you are "paid off" Instead. As Heroules wan said to help the industrious who had a habit of helping themselves, so, perhaps, Satan helps—through the Instrumentality of the trusted captain or mate— thoso who help themselves to the underwriter's money In this honest way. Verily. I hope they also may havo thtir rewards, a hope tbat I am. confident " Sigma," and every other honest mariner, who has a reasonable préjudice against drowning half the crew to enrich scoundrels, must share.

The Harmonious Blacksmith.

P.S—Since tho above was written, I see" Sigma" has taken this subject In hand, ou page 1*4. It Is said that if you mention a certain much maligned person's name, he straightway appears; aud tn thfe

respect "Sigma " emulates him in playing the d

with the popular i'allucv of the balance of trado, but may I ask him It—in a scientific souse oi the word— any profit, other than mutual benefit, ever can result from trait, foreign or domestic? I trow not; if by profit we mean getting the greater value for tbe lew». When I exchange half-a-erowu for a pound of tea, the seller gets no profit in that sense, for he bae given me riatf-a-crowu's worth of tea for two shillings und sixpence; Inilv, it did not cost him so much in money, and the difference is commonly culled bis profit; but it might bo mora truly termed his ira/jes, or remuneration for selecting, preparing, an.I supplying the tea. Perhaps, also, some part of the difference between its cost and rolling price is payment for gratifying our asthetic taste by the extremely artistic decoration of his shop. Surely. when maeh gold Leaf and artificial mahogany ore exhibited for our gratltUaolon, we ought, like the frequenters of that temple of delight, the gin palace, to contribute our proportion of the coat of those decorations which we enjoy. This is no more than justlee to their purveyTyi■ • but perhaps the great proutableoesB of co-operative stores, in whfeh such decorations are as rare as stained windows and pictures in a Dissenting chapel, might go far to teach us that such gorgeous decoration is not absolutely essential fer retail trade, and that people of more quiet tastes, may even manage to get their tea, Ac, without them. But whatever the concurrent conditions, the fact remains, that we somehow get the same value in another form that we part with in coin. As the authorities on political economy express this faot. "all honest commercial transactions are exchanges ol things of equal value" in the aggregate. Bo I trust "Sigma" will see, that although our foreign trado yields no profit, In the sense ol our imports helng of greater total value than our exports, that fact does not necessarily cause us to bo in what he terms "a bad way."

As it is said tbe absence of condemnation is = approval, so "Sigma" is quite welcome to assume that all tbe rest of what be says on this subject will pass muster; In faot, his conclusions regarding tbe accumulation of wealth by Britona, and their proclivity to waste It in foreign loans, when the meet promising works at home are languishing for want of capital, now lying idle, which might bo profitably Invested in them, are quite Indisputable, but he will allow me to remark, that this Is rather tbe remit of our experience of trade morality (Query, immorality) than any prejudice the British capitalist has against invostiDg his money iu home works. We have not yet forgotten Blaek Friday in 1806.

INDUCTION COIL. Sib,—I am building an Induction coll, of which the reel is Wn^long. w.th gmti perchaenels ,ra. thick, 4|ln. diameter. Arguing, In my own mind, that the spark may escape as easily In a lateral direction from one convolution to the next, as from one layer to another, I have begun laying the secondary wire with a strand of cotton thread interposed between them, and this separating of the coils I Intend to increase as 1 in'crease the insulation between the layers. 1 calculate on thirty layers, and the first ten are insnlated thus: First well coated with shellac, next a piece ol tbe soundest brown paper procurable, is cut the exact Bizo, that Is softened In water, glued, and wrapped round as carefully as possible, aud when quite dry, thickly varnished. The second ten will have two thicknesses of paper, and the third three. The primary is two layers, No. 10, and the core an inch and an eighth diameter. I find the work ono demanding, above all things, patience, as, taking stoppages Into account, three layers a week are as much as one can manage. The opinion of fellow workers in the mechanics of science, will oblige.

it. G. Chshihcham.

STRENGTH OF CBAINS.

Sib,—As my only desire was to correct an error in rule, not to poiatoutso small a discrepancy as 001, nor yet cause Mr. Tolhausen to work To 4 placeB of decimals; J> took in band the examplos as given by him paRe 12.1, and gave my reason (why and wherefore) 32 should be used as a divisor or multiple In working oat correctly the examples, page 163. As Mr. T. Invites me, page 186, further to use my skill in working out a moro precise rule, 1 prefer choosing, as an example of rule given by vie, a 2}in. chalu, and show the result in figures without remainder, so that it may be easily understood: 202

Kulc by eighths (as given) — -.-. 50 tons.
8

40i Rule by sixteenths (as given) — = 5.'!J tons. 30 Will any of your readers say this Is correct, or immaterial, showing a difference In this example of 6} per cent.:

iOj Corrected rule by sixteenths — = 50 tons. (Giveu by me, p. 163.) 32

There is no necessity here for a more precise rule, as this is mathematically correct, and will provo In every esse the divisor 32 the only true one worthy of adoption. There la not, and cannot be, any other, not even the nearest approximation (for a rule).

W. N. Lajdler.

TIDE TABLE.

Six,—I cheerfully respond to "Mandril's " request, and 1 shall be pleased to give him any further information ho may require on the subject. I am afraid onr courteous friend, " F.R. A.S.," has entirely overlooked the request of "Saul Bymea" and myself respecting the tide tables. I enclose an exeerpt from the Thantt Guardian for April 2, which indicates the lime of high water at Margate to be exactly two hours earlier than at London BrUii/e. When doctors disagree, who « to decido?

An Initio,

MARGATE TIDE TABLE.—niOH WATIB.

A.M. P.M.

Saturday, April 2 1. a 1.80

Sunday, „ 3 1.34 1.30

Monday, „ 4 2. 3 2.17

Tuesday. „ 6 2.32 2.46

Wednesday, „ « 3. 2 3.16

Thursday, „ 7 3.3-1 8.53

Friday, ,, 8 4.11 4.34

TIME.

Bib,—The question of .r longitude when expressed in mean time, not being equal to x longitude wbon

expressed in sidereal time, admits of a fuller development than has been made on pp. 70, CO, 135, and 119. See letters of "F.R.A.S." aud "Not an F.R.A.S." Thus—180° = 12 hours of longitude, whether the instrument used for measuring it be a theodolite, a menu time, or a sidereal time clock, beeause the idea of duration is excluded. It is angular magnitude, and tbe velocity of tbe clock's hand iu revolvlug through the angle, does not affect the equation. In illustration of this, 1 append the example of page 86. wrought out as nearly correct as 1 can do It, to 4 decimal places of a second, by three different methods.

1st Longitude, considered at Mean Time. a. in. s.

1 33 460710 = Greenwich sidereal time at noon. 1-3333 = Correction fur Mil 7a.of longitude.

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RUSHES.

Bib,—If any pnper-maker is disposed to try the common rush for manufacturing pnrposes, I shall be happy to arrange to send him a supply from Cornwall. Your correspondent, " Bernardln, will much oblige if ho will say how the rush should be prepared for the

Eaper-maker—whether simply to cut aud dry it (as ay) would be sufficient, or should they be supplied in the green state? Also, what would he consider them worth per ton? Cajielfokd.

FUNCTIONS OF FOOD.

Sin,,— Your remarks on "The Value of Different Articles of Food " (p. 107), are reploto with Interest to those that have devoted any attention to the subject. The fallacy of Liebig's classification of the functions of food has of late been shown by the most conclusive experiments of many chemists and physiologists. Their researches have entirely broken down the distinction between the so-called "flesh formers" aud "heat givers " by proving that the former, or nitrogenous, principles are also capable of developing a certain amount of muscular force and heat in the system. Ileuco they are now appropriately termed, "flesh and force producers." Ou the other hand, the hydrocarbons or "heat givers" generate heat and muscular or mechanical force, and are consequently now called " force producers."

Sometime since Professor Frankland, who has devoted much attention to Ibis matter, published tbe results of a series of investigations made for the purpose of ascertaining the maximum amount of power or force which It was possible to obtain from a given quantity of different foods. A notice of these investigations would, I think, be a valuable sequel to your excellent article. In Introducing the subject the learned Professor observes :—

Both tko heat force and the mechanical force generated lu the bodios of animals are derived from food. An animal, however high its organisation may be, can no more generate an amount of force capable of moving a grain of sand, than a stone can fall upwards, or a locomotive drive a train without fuel. All that such animal can do Is to liberate that;store ui" force which Is locked up in its food. It is the cAemica* change which food suffers in the body of an animal that liberates the previously pent-up forces of that food, which then make their appearauco In the form of heat and mechanical motion.

All the combustible Ingredients of food, whether nitrogenous or not, are capable of yielding mechanical force aud heat force; but the nitrogenous constituents, such as albumen, fibrin, and casein, can also be used in the body for the buildiug up of muscle or flesh, hence these constituents are termed flesh and force producers. The non-niirogcuous ingredients of food, such as starch, sugar, and fat are incapable ol forming flesh; thev are force producers only. It is the oxidation of the non-nitrogenous matters in the body which constitutes the chief source of muscular power. The muscular forco expended within the body takes tbe form of heat, and iB the chief if not the only source of animal heat.

The following tabic exhibits the results of actual experiments made to ascertain the maximum amount of force produced by lib. of various ;artides of food when oxidised in the body :—

Tons raised Namo of Food. One Foot

• high.

Cod-liver oil .. .. .. 584s>

Beef fat .. .. .. 6626

Butter .. .. .'. .. 4507

Cocoa nibs .. ., .. .. 4251

Cheshire cheese .. .. .. 2704

Oatmeal .. .. .. .. 2439

Arrowroot .. .. .. .. 2437

Flour .. .. .. .. 2383

l'ea-mcal .. .. .. 2341

Ground rice .. .. .. 2330

Gelatin .. .. .. 2270

Lump sugar .. .. .. 2077

Yolk of egg .. .. .. 2051

Grape sugar .. .. .. 2033

Hard-boiled egg .. .. ,, 1415

Breadcrumb .. .. .. 1333

The lean of boiled ham .. ., 1041

Mackerel .. .. .. 1000

The lean of beef .. .. 885

The lean of veal .. .. 726

Guinness's stout 005

Potatoes .. .. .. .. 01*

Whiting .. .. ..491

Bass's ale .. .. .. ..480

Apples .. .. .. .. 400

Milk 390

White of egg 357

Carrots .. .. .. 322

Cabbage .. .. 201

The maximum amount of viechanical work which lib. of each of the above substances can enable a man to perform (external work) is about one-fifth of the amount mentioned in the above table.* Tbe following tables further illustrate tbe application of these experimental data :—

Weight and cost of various articles of food required to be oxidised in the body iu order to raise I40lb. to the height of 10,coo feet.

External work = Jth actual energy.

Weight

in IB. required.

"166

Name of Food.

Cheshire oheetc

Potatoes ..

Apples

Oatmeal ..

Flour

Pea-meal..

Ground rlco

Arrowroot

Broad

Lean beef

„ veal

„ ham, tolled
Mackerel..
Whiting ..
White of egg
Hard-boiled egg
Isinglass ..
Milk

Carrots ..
Cabbage ..
Cocoo-nibs
Butter
Beef fat ..
Cod-liver oil
Lump sugar
Commercial

sugar

Bass's pale

(bottled).. Guinness's stout

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u bottles [ lOd. per bottle.

«i ., ) 16 74

Weight of various artlaleaof food required to sustain respiration and circulation in the body of an average man during 94 hours.

[table]

* It is not to be understood from this that taking lib. of cod-liver oil would enablo a man to lift ouelii'ih of 56-19 tons (that is. 11:40 tons) one foot off tbe ground. What is meant is, that that is tbe total mechanical work which the combustion in the body or lib of the oil is capable of producing outside the body, supposing its effect to bo wholly expended in the production of this mechanical work without any iconic. Moreover, this statement of tbe amount of work in tons lifted one foot does not take time at all into account. It simply reckons the total work which. it is possible to get out of the combustion of lib. ocod-fiver oil, no matter how long It may take to d"'

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