Abbildungen der Seite
PDF

LETTERS TO THE EDITOR.

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

*»* All communications should be addrtsscd to the Editor of the ENGLISH Mechanic, 81, Tavistockstreet, Covent Garden, W.C.

All Cheques and Post Offi.ee Orders to be made payable to J. Passmork Edwards.

MI would have every one write what ho knows, and as much afl he knows, but nn more; and that not in this only, but in all other subjects: For such a person may have some particular knowledge and experience of the nature of such a person or such a fountain, that as to other things, knows no more than what everybody docs, and yet to keep a clutter with this little pittance of his, will undertake to write the wholo body of p by sicks: a vice from whence great inconvoniences derive their original."—Montaigne's Euaya.

IMPROVED TRICYCLE.

fH3l Sir,—For the benefit of those who are interested in velocipede construction, I send a photograph

[graphic]

and brief description of a tricycle, which, in my opinion, possesses some little novelty and merit. It belongs to a friend of mine, and has been used by him with groat success for the last twelve months. As will ho seen from the illustration, the single wheel behind is the driver, and the pair in front the steering ones. The frame or back, with spring and saddle, are almost identical, both in form ami material, with those of the bicyrlo. It is worked by a pair of hand and footlevers, connected to a pair of 6in. cranks, at qnarter centre. The erauk uxlo is of steel, Sin. in length, and fin. in diameter. It is loose in the nave, so that the cranks are at rest in going down hill. A small ratchet wheel, 'Jin. in diameter, is fixed upon the end of nave, while the axle carries an arm and catch, which work tbe ratchet (see Fig. 2). Tho steering lever is rigidL fixed to the swivel pin of front axle; it is 21iu. in length, and has a hob, 5in. across, which is acted upon by the knees of the rider. Tho swivel-pin and barrel in which it works are inclined away from the rider at an angle of '2'2 degrees; this throws the weight to the inside in turning, and so enBoxes perfect safety in passing sharp curves. The wheels are SOin. in diameter all round; the driving one is hooped with iron, but the two front ones, not having much wear are hooped with leather instead. The distance between the front wheels is 87in. and between the front axle and hind ono, 45in. A tall person would requiro a little more—say 48in. In appearance, this form of tricycle is very neat; being so narrow it partakes, in a great measure, of that gracefulness of form so peculiar to tbe bicycle. I am, however, bound to say that considerable precision is required in its construction: the back must be rigid, and the bearings, especially those of the swivel and driving wheel, must fit well. Therefore, I would not recommend anyone to commence making a, similar one, unless quite sure of good workmanship. For those who are not practical mechanics, but who nevertheless contrive to build their own velocipedes, I would recommend a four-wheeler as being easier to construct, and not requiring the same rigidity or ^precision. With our Editor's permission, 1 will be nappy to forward a short description of a Kght four-wheeler (571b.) which I have used for nearly twelve months, and which has given me great satisfaction, especially in regard to the ease of propulsion. The weight of the tricycle above described, 1 may state, is Sillb.

J. Hastings.

[graphic]

ISOMETRICAL DRAWING.

[84] Sir,—In answer to "Isometros" and T. Smith, I send two photographs of the instrument I mentioned on page 881. The base-pieco B is of sheet iron with the upper edge straight and bevelled off very thin, and with a gap in the middle of about 3 J in. for the pencil to work round in Fig. 1. Tho base supports the expanding crank C, which is graduated to IJin. diameter along its edge, and also supports the pillars PP through the tops of which the long sheet bar N 8 (ISftin. long) slides. Under N S is another smaller Btecl bar E W, fixed accurately square with N S by being driven through holes in the J_ shaped brass casting T. The pin of the crank which is held fast by tho screw seen over graduation 3 on the crank, works in a hole in the J_ shaped plate A A, which is slotted to take the pencilslide, and has also two brass bars to form another slide fastened on by small screws, and this plate also has two pillars P P which slide on tho cross bar E W. Now, postponing the consideration of the rest of the instrument, suppose the crank to be "rotated," as the Yankees say, it is clear that every point of the plate will travel round in a circle, while the plate itself remains always parallel to its original position as the steel bars slide freely in every direction—N-S. E.W., and if the pencil were fastened anywhere in the slot it would make on the paper underneath a circle of the same radius as the crank is set to. Now instead of the pencil being fixed in the slot, it is attached to the middle part of the lever X Y (which is 4in. long) by means of the large milled headed nut Z, and the two ends of the lever X Y slide respectively on the bar N 8, and in the slide A. Now suppose the crank to be set going as before, it is clear that the pencil will be carried from N towards 8, and back twice the length of the crank C, and as the end X of the lever X Y cannot move at all to or from E W, while the other end Y of that same lever does move East and West twice the length of the crank C, therefore the pencil which is attached somewhere between x and j/ will move E. W. a distance proportioned to how for Z is fixed away from Y. If Z is in the middle, then the breadth of the ellipse will be half tho length, and if Z is at .578 of the distance of Y towards X, then the ellipses will be the isometrical projections of circles, as that

is the decimal of""-- = ,—„ The way to /3 173,

use the instrument is to set the crank to the length of the transverse axis of the ellipse required, and to lay the feather-edge of the base plate 11 accurately down on the line of the transverse axis, and to take care that the conjngate axis exactly cuts into a notch made in the middle of the gap in the base-plate close to the centre of the crank. Hold it firm and move the crank gently round half a turn or a whole turn as necessary. I have not tried, but should think that the mechanical arrunge

CHEAP AND GOOD GAS.

[R51 Sir,—" C. D. C." in your issue of July 1, No. 3T.\ has contributed a letter on a means to obtain cheap and good gas, in which he h*a been betrayed into Unconventional habit of abusing the gas companies, when in reality the fault is much oftener to be found on the side of the consumer. He says that when the ga, leaves the retorts it is rich in carburctted vapour, which the gas companies find it convenient to extract. If he knows anything about the condition of gas when it leaves the retorts, he will readily admit he would mw. rare about its being supplied to him in that state, and I don't think he would find it more expedient to use it until some of the condensable matters and other thing* had been got rid of.

When gas was first invented, or rather applied to domestic use, it was supplied direct from the retort*, rich, according to " C. D. C," in condensable matters, and the consequence was, tar siphons had to be attached to each burner, and after many trials, the idea of using it in such a state had to be abandoned, and now, expensive purifying plant has to be provided and worked, all of which, according to "C. D. C," might be disused and the gas supplied cheaper.

Then again, the use of benzole is not only to impregnate the gas with hydrocarbon vapour, but to lessen the heat, and the carbonic acid and sulphuric acid fuji. . which he says are all supplied by the gas companies and charged as gas. If he can invent any apparatus for heightening the illuminating power, and at tbe same time purifying the material. I venture to say it would be no less a boon to the manufacturers than to the consumers.

Then as to his example, it proves the truth of what advanced in the commencement of this letter—that the fault of bad illuminating power is more with the consumers than with the companies. There is an Art of Parliament to compel the manufacturer to keep his commodity at a good and uniform standard, bnt there is none to compel consumers to adopt the best means of nsing the material supplied.

Ho starts by supposing " common gas " to be used in his experiment. I suppose he means that sent ont of the works at about 11 candles, which is about the value ordinarily used. How i* it that he oolygets 2$ candlee out of it with his burner? He is grumbling at bi-ing supplied with an inferior article, and yet he goes the right way to work to make it wor>e still. If he rcaJJv wants good results, why doe* he use a fish-tail burner, when they have been proved aver und over again to bo the worst kind possible for ordinary "Newcastle ga*? When his gas is carhuretted by using 1\ pint ol naphtha per thousand—an item that will run up in large consumption—he only gets 7 candles, whtTea*, if he used an ordinarily good batwing, he would get about as much without any naphtha at all; and by using an Argand burner, he would, with a consumption of 4 to 5 cubic feet per hour, get a light equal to 13 or 14 candles, without any trouble; of course tho losa in illuminating power would be in proportion to the distance he is from the works, and the state of tho maim and services. I repeat, good burners are the only means of getting a renlly satisfactory result, either ia power or cost; for he says, even with highly carburettei

[graphic][merged small][merged small]
[ocr errors][graphic][merged small]

NEW LATHE BY GEO. PLANT.

[86] Sir,—You have published in your most valuable journal a print of ono or two lathes by different milker-. I therefore venture to enclose a photograph of ono that has been recently built for me by Mr. George Plant, of Alsager. I trust the photograph will sufficiently explain itself, but as I am only, as in turning, an amateur, I will give yon a fow particulars. I have, of course, pat as much as possible into the picture withont any reference to the possibility of their being worked in combination, and this any turner will at once see.

Tin- lathe is a screw-cutting one, with the usual

change of wheels, the leading screw passing through the bed. The slide rest, when in gear, can then bo either worked by the treadle, or if in spiral turning by the handle seen in front of the lathe. The head-stock has seven divisions, and the pointer or index is capable of being fixed in front, as showu, or at the back, which is often more convenient. The lathe has, of course, the usual micrometer screw arrangement, and the overhead motion, which latterhas, by lever-sliding weights, a power of tightening or loosening the bands for driving the cutting frames. The photograph represents the geometric chuck on tho mandrel, and the eccentric and elliptical on the bed. In the slide rest the elliptical cutting frame is placed. Beside these Mr. Plant has

supplied tho spherical and spiral chucks. All the ot'ier cutting frames, including the rose engine frame, wore supplied by Messrs. Holtzappfel & Co.

Hanbuf.y Barclay. Handsworth, July 12.

READINGS FROM THE GLOBES.—VII.

[87 J Sir,—Although numerous wonderful and most important discoveries have been lately made by means of light, as may be sten by the papers contributed to your periodical, "What Stripes the Sunbeam," yet there is one thing connected with it which was known not only to oar immediate ancestors, bat which showed itself to the gaze of all when first the beams of the Buu began to Bhine; for.shndow is obvious to the view of all, and, like it* parent light, has been the" occasion of wonderful discoveries. When a ray of light is intercepted, by an opaque body it is obstructed in its course, and shadow is the consequence. If it were intercepted by a transparent substance it would be refracted with greater or lees force, according to the density of the substance; but whore the body is opaque, it is not refracted, but obstructed, and the ray on each side of the shadow still proceeds in a straight line, thus furnishing another proof that a ray of light passes along in a straight line. Shadow affords the means of explaining eclipses a.4 well as of ascertaining the distance of the sun from the earth. We can also teU by means of shadow not only the time of the day, but the altitude of the sun, and consequently what sign of the zodiac he is shining in, for as it was explained in a former letter he gradually ri.-cs from a meridan altitude of 15" in our latitude, until he has reached tht-meridan altitude of &T. When then his meridian altitude at London is 15", he has just entered Capricorn ; add t,> this 'J3.J , his greatest declination, and his meridian altitude will be 38|\ at which height he will be in the equinoctial, add auothorSSA , his greatest north declination, his meridan altitude will then be 0*3 , when he has just entered Cancer; thus his difference of altitude on each side of the equator is equal to the extent of his declination. Now it is obvious to every one that when his altitude is low the shadow of any object will be long, as Cowper Bpc along of his legs, says:

Mine spindling into longitude immense,
Provoke me to a smile: the shapeless pair
A» they, designed to mock me, at my side
Walk step by step along the plastered wall,
Preposterous sight, the legs without the man.

The greater the altitude the less the shadow ; and ■when the altitude is 45J, or halfway between the zenith and the horizon, the shadow is exactly equal in length to the height of the object which throws it. Thus, if a man lift, high cast a shadow Oft. in length he might then know that the altitude of the sun or moon was 45 , Hence it is obvious that there is a proportion subsisting between the altitude of the sun and the shadow. That

Eroportion is expressed by the following formula: length of shadow : height of gnomon :: ft : tang, of the altitude. It is in consequence of this variation of the shadow that the ancients have divided the inhabitants of the earth into different names according to the shadows which they throw, as may be seen by the figure. The inhabitants of the torrid zone are called Ascii and Ainphiscii—signifying without shadow, Ad shadows on both sides of thein,—because when the sun is vertical, or exactly overhead, no shadow is thrown, which is at twelve o'clock in the day; and it is equally clear that the shadows of these people will be thrown both northwards and southwards, us for example, at the equator, when the sun is north of this line the shadows of those living there will bo cast southwards; 0ut when the sun has south declination, they will be thrown northwards. The higher any celestial object is astronomers tell us, the greater the light and the more intense the heat, so that the vertical rays of the sun must dart with great force upon the heads of the inhabitants when no umbrageous tree affords its friendly branches to protect them. The inhabitants of the temperate zones have the name Ileteroscii given to them, which is also derived from two Greek words, and signifies those people who have their shadows opposite to one another at twelve o'clock in the day. Thus we living in the north temperate zone always see the sun in the south at twelve o'clock, and as the shadow is .ilways in an opposite direction to the sun, we cast our shadows northwards, and onr Heteroscii are those living in the south temperate zone, who, seeing the sun in their north at twelve o'clock, must cast their shadows southwards; and of course the nearer we go towards the torrid xone, the shorter will our shadow become. Those who live in the frigid zones are called Periscii, because when the sun is above the horizon their shadows will Mo all round them. In the north frigid zone, for instance, at twelve o'clock in the day the shadows, like those in the north temperate zone, will be thrown northward, but as the earth revolves on its axis, its inhabitants will be carried to the other sido of the north pole, and consequently at twelve o'clock at night their shadow will bo cast southward. This may be easily understood by the direction of the shadow in our latitude in the summer time, for the shadow of the gnomon on a horizontal sundial will go round a large part of the circle, and if the sun were above the horizon all night it would then go completely round tho dial. The inhabitants of the frigid zone, then, will cast a shadowin all points of the compass in the course of twenty four hours. * T. S. H.

UNEQUAL STEAM PRESSURE.

[88] Sir,—As far a-i the use and practice of the indicator is concerned, I say that it will not tell the engineer everything abont the steam engine as Mr. Wood pretends. For instance—a valve is l-10th bite, same as the figure Mr. Wood put in his lust. The indicator did not say to him that he must move the excentric forward lin. to compensate for it; or if he went to an engine that hod no lap on the valves, and he B»w that it would do with as mnch lap on as would cut the steam off at half-stroke, the indicator never told him how much Up he must put

[graphic]

on to effect this purpose. Nor does'the engineer expect it to do so, for he knows that this must be obtained by minute calculations on his part. If a man, "strictly speaking," must diffnee such knowledge as Mr. Wood has been attempting, ho must not only have a thorough knowledge of the indicator, but he must know the traverse of the valves, width and depth of steam ports, and he must also know the amount of modification the vulves have. To illustrate it we will take "Inquirer's" case. If his low pressure engine valves have more modification on the edge than required (which seems somewhat manifest in the figure), he would have to pnt them forward unnecessarily to compensate for what they are veed too deep, thus inducing an unnecessary amount of hip on the high pressure valves. Just to illustrate that the modification of the valve edge would alter the amount vi hip on the high pressure valves, we will suppose that the piston required in the vee aperture of the low preisure engine valves uu area of 6in., to compensate for them being late, tho vee to be Gin. x 2in, on the edge, which would be an area of Gin., when the valve traversed from bottom of vee to the top "iin., what the piston required. On the other hand, we will suppose the vee in valve edge to be 4in. x yin., which would give out the same amount of area as tin- firht Gin.; but to effect this the valves would have to traverse Sin., instead of 2iu., so that the excentric would have to be put forward more in the latter case than in the former, thus inducing more lap to l>e put on tho high pressure valves in the latter illustration than in the former. Now, air, I contend that Mr. Wood cannot, as he said at the outset, tell how much "Inquirer" must put his excentric forward, except he knows the precise amount of this modification. As he can't tell how much the excentric must be put forward, it is useless for him to say how mnch lap he must put on the high pressure valves.

Now, sir, the original information which he gave to "Inquirer" was too definite to admit the evasion which he has attempted in his hut, by saying that it is an easy matter for any man who has a number of engines under bi^ care to loose the excentric, and put it forward sufficient to make the low pressure valves steam soon enough, and then take the high pressure valve covers oil, so that he conld see what amount of hip those valves required. This information seems somewhat better than the original, but ho would not most probably give it in this form, hod it not been for what be considered my opposition. Again, the information is as much at fault, when given in this way, as the original. Though he can see the amount of lap that would be required on one Bide, when he turned the engine round to the opposite side, he would find to his disappointment that the other valve would either require more or less hip. He has not told us what he would do in that case. I expect he would do the same as many others I have met with—i.e., put on unequal lap. Engineers of practical experience believe in equal steaming, but to effect this purpose they, unlike Mr. Wood, expect to get equal steaming and equal motive power, when they have equal aperture in valves, equal expansion, or cutoff, equal exhausts, and the exhausts to close up equal, on both sides. If engineers don't get equal steaming with this sort of volvo setting, they at once inquire what is the cause. If they find it to be induced by unequal balancing of the working materials they at once set to and remove the cause, by patting sufficient balance at some convenient and effective point in the machinery. On the other hand, if they discover that it is induced by the angularity of the beam or the unequal angling of the valve levers, they at once set them right. But Mr. Wood adopts the earliest dodges almost on record—i.e., of screwing this nut a bit and the other a bit, a practice I am happy to know has passed long ago into oblivion in the eyes of progressing engineers. It is impossible to get u good figure in this way, or equal steaming and equal strains in the machinery. Again, if any brother reader requires information through the medium of this paper on engineering, it would be far better for those parties who require it, and more credit to those who volunteer, to give it in as direct a manner as possible, instead of the way which I have just quoted. Again, he says in another place of his last, when illustrating his cose, that the valves of No. 2 engine are }in. late. Well, we will pnt the excentric forward, so as to make these hist valves right. We shall then require 7in. of lap putting on the short slides. Now, sir, it does not follow that because both sets of valves are driven by one exceutric that they are of one traverse; but they evidently must be if the low pressure valves want putting forward £in., and then {in. of lap putting on the high pressure valves to compensate for it. What I said "Inquirer" must do was that he must put $iu. of lap on the exhaust side of his valves (supposing that they steam from inside). We will suppose that the valves are iin. open on the exhaust side when in the middle of their traverse. Now let " Inquirer " put Jin. on each side of the valves on the exhaust side, then the valves will cover the ports on the exhaust side Jin. Now let him shorten the rods between 4iu., that will bring the exhaust of tho valves to the same point from whence they started, |in. open in the middle of their traverse. This done, he has pnt Jin. of lap on the steam side of his valves, and not the exhaust, as Mr. Wood has said. The reason why I prefer lapping valves in this way is because very frequently tho steam sides of valves are veed or havo an uneven edge, which makes them more difficult to put bits on; but the exhaust side of the valves being always straight across the edge, or even, makes them very easy to pat bits on. In fact, I have had bits put on nearly as soon as I could have the rods cut and pieced up again. But I don't look at time so much as

I do good workmanship in these ca«e». for U * j<a of this sort is worth doing at all it w worth Oo1k well.

I say, again, if "Inquirer" gets equal ftteanii*; with this amount of lap be will have no eompreseiou Ii his high pressure cylinder. (By ennal steaming I Uhj* equal valve apcrtnres.j Mr. Wood's plan i-tnid*. in the other ease) the valves to be Jiu. open in U; middle of their traverse, to put }in. of hip on the Swaei side by shortening thf rod* between lin. If the v*lv steam from inside that brings the valves on thf «■ haust side $in. open, when in the middle of their traverse. Yet he says the expansion is the baxne in both cases. Now, sir, as steam cannot be expanded in uy cylinder with slide valves attached without making them longer on the face, it is evident that Sir. Wood completely stultifies himself. In cylinders that ar. Btcamed from inside by slide valves, expansion can on); take place from the point where the i-team U cat off to the point in the valve's traverse where the exhaust side of the valve conies in actual contact with thf cylinder port, thus taking away the steam from the piston.

J nst to illustrate this I will ■appose that we have an engine whose traverse is Din. and the ports Sin., thvalve face to be just sufficient to cover the pork—i.r„ no lap on either aide. This arrangement would cam the steam on the piston the fall length of the stroke pretty near at the same pressure as at the comment* inent. This is what we understand as no expansion Well we will put Sin. of lap on these valves, not in the same way as an engineer, but in the same way as Mr. Wood advises us—i. e.t by shortening the rods between 6in., that would make the exhaust aide of the valves wide open when in the middle of their traverse. A Miiotu position that. This arrangement vouldcuttbe*teaniofi at half-stroke with Din. traverse; and as the valve-fact1 had not beeu lengthened at the very identical spot where the steam was being cot off for the pnrpoa* of expanding it in the cylinder the valve would open ou the exhaust side, and thus prevent expansion of steam from taking pine*. The valves, as well an exhansting sooner, return in their own traverse sooner, in the some proportion as he added le>> by hbortening the rods between. Yet Mr. Wood fell* cs that the expansion is the same in both case&. The diiTerauce there wouJd be in these two caava tint Mr. Wood's mode of lapping valves would be t-i strain tho machinery without any profit the first part of the half-stroke; the last part, the engine would have to run without any motive power behind the pialon to support it* motion. In tact, the engine would be incapable ot running if it had any work to do. He *anti me to tell him how to Up vulves without incre.a.-ui; tire pressure at the commencement of the stroke 1 have no idea, that I can do that as a rule, except iu engine* that have, no lap on the valves und the vacuum is vtry bad; but undi-t such bad circumstances as theae we may Up valves to a certain extent without increasing the pre>«w *t the commencement of the stroke. Again when 1 lap valves <unlike Mr. Wood) I expect it to be a prout by reducing the terminal pressure in a greater ratio: hence the gain. Mr. Wood's practice u such that it strains the machinery wheu there is no chance of the terniical pressure being in any degree altered for the best, to No. 254 I find him giring "Relivot" information similar to that which he has been dealing out to "Inquirer." Without knowing anything about the petit arities of the engine's construction, he says "Relirel must put $in. of lap on the steam-side of his valves:^ in the next breath he says he must cut as much oD fe exhaust side of these valves. Now, sir, this would tun the effect of straining the machinery without in uj degree altering the terminal pressure. For just * much sooner as he put the excentric forward, to compensate for the lap, it would begin to exhaust. Tik« is nothing gained by lapping valves in this way ex«.pi unnecessary strains, as far as expansion of steam o concerned. Again, he talks about the practice an4a>of the indicator being a^nr art. I t-ay that the prfc tico and use of tho indicator is a scieuce, not an fcrt; hence science is knowledge. Art is the application» that knowledge to practical purposes. When & engineer succeeds so far with the ust» of the indje**r as to understand its delineation on thie paper, then. »£! not till then, will he be able to convert its teochiuf>practical purposes. Now, sir, I contemd that &ud * formation as Mr. Wood has beeu giving to "Inqw* and " Relivot" cannot be diffused without knowing***particulars of the, engine's construction. Again ^ boasts of his superior knowledge of diagrams, aw* the many of your numerous readers who can speak >■■ his good judgment of the same. Well, we let p&roa speak when the spirit moves them in this direction. A* far as my judgment goes the very figure which he ga^ to "Inquirer" and specified to be good, a progressive driver would scarcely consider worth his notice; and I should think it would be much less so with a progressive engineer. Edward Malbo>'.

PRE-ADAMITE MAN.

[89J Sir,—Would it not have been better had JSargent, jun., enquired into tho above >ubjeet somewhat more ere he challenged public discussion in the columns of your valuable journal—a journal, let me say, which I have always found to be devoted to the notice of really useful and instructive subjocts of general interest to its readers. Surely your correspondent cannot haT«? read the "Book of Books," and compared the narrative of the Creation with the opinions enunciated by oar best modern geologists and paleontologists, or he would never have made such an application as he docs m your last number now before me. Had he doP* w>» m" "stead of doubting the truth of the Biblical account, he must have been compelled to acknowledge the perfee* tion oí the divine order of creation, inasmuch ¡is man could not possibly have existed at the same period as those monsters shown in the fossil state at onr British M a se am, and by models in the grounds of the Crystal Palace, the earth not being then in a fit state for his reception.

Man being: the crowning work of God, required that every subordinate thing should be previously perfection; and let sceptics sneer as they will, every new discovery only tends to re-verify the truth of the Mosaic description leaving out all theory as to the duration of each

'* day '* mentioned therein.

Had man existed with the Ichthyosaurus and Plegiosaurus, «fcc., undoubtedly we should have found his bones as well as theirs, but such is not the case; and so for as I can learn, no instance has been noted of the discovery of human remains in any deposits except those of very recent times.

As one who signed the declaration of students of the nntural sciences in connection with the scriptural account some four years since, I am not disposed to enter into any argument as to the truth or error of the latter, but I would certainly advise Mr. Sargent to look carefully at the subjects I have named and take—say Richardson's "Geology and Palaeontology," published by Bonn, at about 5s., and make comparisons. If those do not convince him, I am afraid that no number of letters in the English Mechanic will do so.

T. S. Conisbee.

[90] Sib,—I see in the English Mechanic for 8th July that one of your correspondents wishes for a discussion of this matter. By "Pie-Adamite Man" I suppose he means pre-historic man. The use of the phrase "pre-adamite" is rather unfortunate. With Adam we have nothing to do, and we only raise a certain hulhvballoo if we speak of his predecessors. In our discussion of matters on natural science we have nanght to do with what is called theology; that is a science to itself—having in it much that is true and much that is false. Adam may have been the first man or he may not. Science does not care to ask. All Science wants to know is. Whence did man come and when? The latter of these questions is the one your correspondent, I presume, wishes to raise. I suspect few will at this day restrict the period of man's existence upon the globe to the six thousand years until now prescribed to it. The nnmerons discoveries of Hint flakes made within the past few years—the conclusions to which learned and thorough students of ethnology and geology have been forced to come—new truths learned from comparative philology and new insights gained into man's geological relatione—these and other things have led most of our leading men of science to at any rate this conclusion, that the age of man as a species is not to be reckoned by thousands of years. Were it not that the opinion forces itself upon us that this subject is not the one best adapted for discussion in a journal designed for workmen rather than speculators, we might proceed to flu pages with a précU of what has been done in this department of science. Those who wish to make themselves thoroughly conversant with the subject can do so in the pages of ¿yell, Page, and others. To those who only wish to know the general conclusion to which scientific men have come perhaps the following may be of nse. I extract it from Page's "Man—Where? Whence? Whither?" "Historically we can have no certain evidence of the outgoings and incomings of those early races which preceded all history. Even were tradition reliable and history certain, it is as impossible for the race as it is for the individual to trace itself back to its origin. We can only arrive at a notion of man's antiquity by inductive reasoning from the evolutions of nationalities, tho growth of language and the progress of civilization; and the induction for all

S re-historic time must be founded exclusively on the Lscoveries of geology. Geologically there is the amplest evidence of man having been an inhabitant of western Europe for ages preceding the popularly received chronology. Man's occupation of Europe does not fix the measure of his antiquity in northern Africa and Asia, to which everything points as the region from which the races of Europe were descended ; and the discovery of pre-historic remain* in Asia cannot be regarded as the earliest indications of the human race ; bnt geology must seek for the earliest traces of man in the regions that are now occupied by the lowest varieties—thus implying an antiquity for the human species that cannot be expressed in years and centuries, but only relatively to other geological events." We may, I think, regard this as the conclusion which geology forces upon us—viz., that man has existed for ages, bat that he is the Uut of the series of organized beings « he is the greatest. H. P., Hull.

PEDESTRIAN TOURS.

[91] Sia,—I have been a subscriber to your delightful and ever-improving periodical for nearly two years, and have derived much valuable assistance from it in ray efforts as an amateur astronomer. I am glad to see the subject of pedestrian tours now engaging attention, and I write in the hope that I may be able to give, as well as receive, some information. For several years past I have spent my summer vacation in rambles through various parts of England and Wales, and can therefore speak practically as to the best mode of successfully carrying out such on expedition, and of the delight which may be derived from it. I have just returned from a week's ramble through Sussex, in which I have been solus, and during which I have visited many places, having walked upwards of 100 miles. In 1864» I took nearly the samo route as that mentioned by your correspondent "B." in your last number, except that I started from Rhyl, and ex

tended my walk through Conway and Oswestry, as. far as Shiffnall.

I have no doubt that many of your readers would like to undertake such a tour if thoy knew how to arrange it inexpensively. When I did the above-mentioned trip in company with a friend, we spent 11 days in walking, and I And from my diary kept during the tour that my share of the expenses came only to ,£'J Is. Hd. If we had adopted the plan suggested by "B," of breakfasting at a good hotel, our expenses would have been very much heavier. Our method was to sleep at an inn, to btart on the first thing in the morning, and prepare all our meals out of doors with portable apparatus which we carried in onr knapsacks. If any one wishes for information with regard to this apparatus, I shall be very glad to give it through your pages.

I want to get a hint or two, from any reader who has had experience in such tours, as to tho best sort of boots or shoes for walking. I can walk any distance without becoming leg-tired, but with ordinary covering for the feet I get blistered feet, and this very much interferes with the enjoyment of such trips. In return, any information which I can furnish to intending tourists, either as to routes, places of interest, good and cheap houses for sleeping, or arrangements with regard to provisions, Ac, will bo most gladly given.

Brighton, Sussex. Scholastici's..

A CURIOUS SENTENCE.

[92] Sir,—The following is a curious sentence, and if you think it worth inserting, it will, I have no doubt, interest many of your readers.

"Sator Arepo Teret Opera Rotas."

English :—Cease from your work. The sower will wear away his wheels I

1. It spells backwards aud forwards the same.

2. Tho first letter of each word spells the first word. The eecond letter of each word spells the second word, and so on with the third, fourth, and fifth letters.

3. Beginning with the last word, the last letter of each word spells the first word, and во on with the fourth, third, second, and first letters.

Reg. Pilkington. Heads-buildings, Bridgnorth.

LUNAR COSMOLOGY.

[93] Sir,—A continued series of critical observations of the surface of the moon, by the aid of snperior telescopes and repeated examinations, do not tend to establish the feeling that any corresponding physical resemblance upon the surface of the earth can be identified with the surface of the moon or suggest like causes of operation; but, on the contrary, in nearly every particular the surface of the moon is different to the surface of the earth, and also in the smaller gravity of the materials and the absence of meteorological influences in altering the surface daring vast periods of time.

Probably appropriate lunar names will ultimately be nsed to distinguish remarkable and special appearances, and the words "seas" and *'roieanofe"will disappear from the fanciful and poetic descriptions intended to represent popular resemblances to types on tho earth. It is contended that the moon, as it at present exists, is the union of what once were vast numbers of small spheres, with fluid interiors, of different sizes; that rings surrounded the earth like the rings round Saturn; that these rings were composed of an aggregation of small satellites; and that the whole identical mass of matter in a half fluid state has^by the coalescence of the materials been united into one moon, and left traces of the multitude oí small hollow spheres in the numerous craters and circular ridges, in the form of wrecks, which in some respects slightly resemble the craters of volcanoes, on the surface of the moon.

It is possible that the diameters of the small satellites varied from ten yards to 20,OUU yards, and an ideal section of the moon in any direction would reveal the mechanical amalgamation of a variety of fractured spheres, and indicate the antecedent conformations. Perhaps any general inspection of the sectional interior of the moon would confirm the theory. The transformation of these flat rings, composed of an aggregation of small spheres or satellites, into one moon by an operation of gravity is one of the grand events of the past in lunar cosmology.

The vestiges left on the surface of the moon are chiefly the shattered remains of former small hollow globes, and these significantly indicate the relative proportion of thickness of the outer crust or shell and the relatively fluid matter in the centre of each small sphere. Probably the pleasure of tracing back some of the changes on the surface of the moon will appear as interesting as any intelligent investigation into natural history when contemplated as the work of immutable laws and the proof of design.

As a theory, the modus operandi will supply matter for discussion, such as the mineral characteristics of tho interior fluid mass of each sphere, the distribution of the fluid masses over some parts of tho surface of the moon constituting an appearance of flat planes, settlements, and floors, but still thickly filled in with the vestiges of former fragments of outer shell, and partially submerged in what was once relatively finid mineral matter liberated by the fracture of the outer shells. In some directions, and radiating from a centre, these fluids give the appearance of the streams of lava from a volcano by the last distributions and settlements of the typical lava of the buret shells of the spheres or satellites.

At the same time that this great convulsion took place, an equally salutary provision was made upon the surface of the earth in the precipitation of the

entire mass of tho waters of the ocean for the first time on the surface of the globe, and providing a permanent medium of ultimate stability in the liberty of this mighty ocean pendulum. From this period meteorological changes took place, and the full developments «f organized beings, by suitable climates, in almost infinite variety and in systematic order, adapted to the prepared conditions of the surface of tho earth, were perpetuated by selection.

Littus HABF.T Conchas.

SHIPS' PUMPS.

[M] Sir,—Permit me to thank "G. A. S." for his reply to my query, "The Goat and the Grassplot." 1 wish the above gentleman, or some one conversant with the subject, would inform me what he considers to be the best purcha.-e for ships' pumps. The wee-gee and fly wheel are the best I know, and answer the purpose generally; but if a vessel spring a leak either will soon exhaust a crew, which I know from experience, having had to keep *J'2 hours at the latter purchase, after my crew were exhausted, in 16H5. I have materially assisted tho wee-gee by making a pendulum of "a 121b. shot; but something much better than that is needed, leaving steam out of the question. Capt. Baxter.

85, Crane-grove-terrace, H olio way-road.

THANKS.

[95] Sir,—I feel that I shall bo doing no more than to echo the sentiments of your optical readers by returning sincere thanks to your talented correspondent, #the Rev. T. W. Webb, for his uble exposition of the abstruse and difficult intricacies upon which optical definition depends. Such information from such an authority, aud in a style su felicitous and unassuming, must, 1 am sure, elicit the warmest admiration of all, while it constitutes a painstaking und truthful analysis of principles which are generally too imperfectly understood, but are nevertheless of the highest optical importance.

W. Purkiss.

THE OPTICAL BRICKLAYER'S TELESCOPE.

[1)6] Sir,—I am afraid that " Optical Bricklayer" may be a long time discovering the merits of his 7$in. mirror, unless he adopts a more systematic method of proving its figure. Perhaps the valuable letters of Mr. Webb may help him to do this; if not, I would advise him to test it by the process described in the last volume of the Mechanic, pages 832 aud 857. This will set his mind at rest once and for ever as to the actual figure his mirror has.

The heavenly bodies are, perhaps, as a rule, about the most unsatisfying things which can be selected at tests of a powerful telescope, and while stars may no doubt render important service in the process of testing, on account of the almost infinite parallelism uf the rays which proceed from them, why they should be considered test objects when focussed in the ordinary way, I am quite at a loss to know, and why it is that objects that are so exceedingly sensitive to atmospheric inequality as to be always changing, should be selected as standards of comparison is an enigma that I must leave to others to solve.

It certainly seems feasible that a in order to become so ought to be as exempt from change as anything can be, and not bo subject, as a star is, to endless distortions and caprices of the atmosphere. In this particular a thermometer bulb in sunshine has no doubt an advantage over a star, but a watch dial can scarcely be a test of definition with a large telescope, although it may be a moderately good test of achromatism in the case of a refractor; but, whatever test is used, the proper time for its observation (even with terrestrial testsj is of great importance. Noon is generally a very bad time. Perhaps the best time of all lor steadiness is generally about one or two hours before suusot, especially alter a cloudless day. "Optical Bricklayer " need not be at all surprised he cannot get on with Saturn. I may tell him, as an example of this, that two evenings since I was looking at Saturn with a 9in. reflector, aud 3iu. refractor simultaneously, and I got decidedly better definition with the 3in. than with the 9in., although the defining and separating power of tho mirror is more than double that of the refractor. This simply shows how much atmosphere and upcrture have to do with definition. As to stars, a power of 120 on a 7Jm. mirror, is scarcely enough at any time to give clear and sharp discs. Double that power would bo far better if the mirror is truly figured; but, with every precaution, doubts may still arise, unless a mode of testing is used which does not depend on atmospheric conditions. W. Pcrkiss.

SECRET CODE FOR TELEGRAMS.

[97] Sir,—I purchased in London the other day a small work described as" A Secret Code for Telegrams. &c.," which I find has been extensively advertised and recommended. I think, however, that the author should acknowledge that hissystem is merely a rechauffeч with some very useless condiments, of one of the many methods given by Uishop Wilkins, in his "Mercurie, or the secret and swift messenger." The four imposing puzzle pages of alphabets at the end of this "Secret Code" made mo at first believe that something new was concealed under them, bnt by using tho worthy biehop's method I succeeded in producing the exact cypher of this modern writer, using his own sentences as examples. The method adopted by Wilkins is to write down, first the alphabet in its ordinary form, and under the letter A to write in a vertical line tho letters of any selected word, completing the several alphabets as below—key-word " mines."

A B C D E Ac.

M N O P Q 4c.

I J K L M <fce

N O P Q H ic.

E F G H I &c.

8 T U V W 4c.

IE it were required to write the word babe the first letter would be N, which stands under B in the first line, the next I, which is under A in the second line; the third O, which corresponds to B in the third line, and the fourth I from the fourth line. Tho next letter would be taken from the fifth, and then the first, second, &c, would be used again in order. Our " Babe," then would be NIOI. The cypher words would be always of the same length as the key-word, a space being left as the last alphabet is used. The difficulty of this cypher consists in the fact that the same letter has several different signs ; thus B is first N, then O, whilst A and E are both represented by I. This cipher is described in full in the edition of Wilkins, published 1»02, vol. ii, p. 139. It has only one objection, however, which is this, that if any particular word be certain of being found somewhere in the cypher, such as a proper name, or the title of a racehorse, 4c, the whole can be unfolded iu a few minutes. Ii a few details of this method would amuse your readers I will willingly write again. I have no wish to injure the sale of the little book, which is cheaper and more easily procurable than Wilkins's, and contains also an ingenious notion as to numerals, which I have no right to publish. I do not doubt his good faith, and can fancy his exclaiming

Pereant, qui mea ante mc dixerint, or, in the vernacular,

Confound the nasty scribes,and those who taught them, Who thought my thoughts before I ever thought them!

CRYPTOGRAPHER.

ELECTRO-PLATING AND GILDING.

[96] Sir,—I think M. Schneider [4228] will find the following a most efficacious method to pursue for electro-plating and gilding. The solution of silver used for plating consists of cyanide of silver dissolved in cyanide of potassium, which may be prepared in various ways. The method generally adopted is as follows:—Metallic silver is dissolved in four parts of nitric acid, diluted with one part of water; the diluted acid is heated in a vessel, and the silver is added by degrees. M. Schneider must avoid breathing the fumes which ascend, as they are highly deleterious. The metal being dissolved, the solution is emptied into a larger vessel and diluted with water. To this is added a solution of cyanide of potassium, so long as a precipitate is formed. This is cyanide of silver. When the precipitate has settled, the liquid is decanted, and the precipitated cyanide of silver is thoroughly washed Bo as to effectually dissolve out the soluble salts. A solution of cyanide of potassium is then added to the precipitate until it is all dissolved. The resulting liquid constitutes the cyanide of potassium and silver, and forms the plating solution. It ought to be filtered previous to using, as there is nearly always formed the black sediment composed of iron, silver, and cyanogen, which, if left in the solution, would fall upon the surface of the article receiving the deposit and make it rough. The cyanide of potassium used to dissolve the cyanide of silver may be so diluted that the plating solution, when formed, shall contain loz. of silver in the gallon.

Articles that are to be plated are first boiled in alkaline ley, to free them from grease, then washed from the ley, and dipped in dilute nitric acid, which removes any oxide which might be formed upon the surface; they are afterwards brushed over with a hard brush and very fine pumice (known by oilmen asFFFF). The alkaline ley should be in a caustic state, which is easily effected by boiling the carbonate with slaked lime, until, on the addition of a little acid to a small drop of the solution, no effervescence occurs. When the lime has settled, the clear liquid is fit for use. The key should have about .'lb. of soda ash, or pearl ash to the gallon of water. The article being thoroughly cleaned and dried, has a copper wire attached to it. It is then dipped in nitric acid as quickly as possible, and washed through water, and then immersed in the silver solution and attached to the battery, as at A in Fig. 1. In large manufactories, where a great many

[table][graphic]

things are plated, a Bunsen's battery is used, but fo amateurs a Daniel's would be best. The article is instantaneously coated with silver, and ought to be taken out, brushed, and replaced. In the course of the few hours it is taken out again, brushed and polished. Fig. 2 will illustrate the plan pursued in large establishments. D is a large vat containing solution; B and C are two brass rods placed along the top of the vat and to each of which a wire from the battery is attached. The advantage in this arrangement is that you can have more than one rod across the vat from each pole as a, a', b. This plan is generally adopted when there are a great many articles and it becomes

necessary to use more than one plate. If the object has been already plated and part of the silver has worn off, the whole ought to be separated. The solution UBed for stripping off the silver is composed of strong sulphuric acid (vitriol) to which a little nitrate of potash is added; the article is laid in this solution, which will dissolve the silver, without materially affecting the copper, Ac.; saltpetre is added by degrees, as occasion requires; and if the action is slow, a little heat is applied to the vessel which contains the stripping solution. The article should then be polished, cleaned and treated as above.

The solution for gilding is made by dissolving gold in four parts of nitro-muriatic acid; water is then added, and the solution is treated with cyanide of potassium in the same way as silver. The solution should be heated when used. It is advisable to plate all articles before gilding. Three minutes will be quite sufficient to gild any article.

Before regilding articles which are partly covered with gold, or when the gilding is imperfect, and the articles require regilding, the gold should be removed from them by putting them into strong nitric acid, and when tho articles have been placed in the acid, by adding some common suit, not in solution, but in crystals. The articles should then be polished and treated in the usual method.

Thus far, Mr. Editor, I have endeavoured to answer M. Schneider, and shall be willing to reply to any further queries that I am able.

258, Kingsland-rood. Walter J. Nicholls,

[graphic]

SQUARING THE CIRCLE.

[09] Sir,—Seeing that one of your abler correspondents in last issue of the English Mechanic has tried so impossible u fi task as that of squar

Z^h^ ing the circle—I mean the rectifying of the circumference of the same figure—you will no doubt allow me to give to those interested in the subject a more precise and perhaps more valuable construction through the medium of your columns.

I refer myself to figure annexed, so as not to encroach too much on the space offered to your subscribers.

A diameter has been drawn through a circle, and produced in the direction of R, the radius divided into five equal parts, and three of these separate parts carried from B to C, D, and E, so that if the diameter be represented by d and the radius by r,

AC=i!',AD=i^andAE , 1*
5 5 5

A G is B perpendicular to the said diameter, and F a point on the same, fixed so that AF = r, and A G may equal the linear distance F C. F has been joined with E, aud through G a parallel to F E (G II) has been drawn, intersecting the prolongation of the said diameter in II. AH represents exactly up to the 5th decimal incl. the rectilinear length of the circumference, for by similar triangles AFC and A Q H, we have

AF:AG = AC:AH, or substituting known magnitudes for the above quantities, and remembering the Pythagorean proposition as well as the construction, wo receive

[table][ocr errors][ocr errors][merged small]

therefore, taking the diameter to be unity, wo have

A H = 8-1415919 .... which result shows a difference in the first seven decimal places, when compared with tho Ludolphine (w) of seven units in the seventh decimal, and not already in tho second, as in Mr. Proctor's solution. A Member Of The English Mechanics' ScienTific And Mechanical Society.

GREAT CIRCLE SAILING.

[100] Sib,—Seeing in theMECHANicthat " T. S. H." and "L. M." had found the distance from Cape Good Hope to Port Jackson to be 0,815 miles and 0,824 reLi. spectively, and having travelled that distance several times, and always reckoning it to be under 6,000,I computed the distance, and found the results as figured. Well, this did Sohth Pole not agree with theirs. I tried it again, and again still the same results. I then computed it by "Mercator's" principle—{i.e., supposing the earth to be a plain), and found it to be 5,729 miles, which comes nearer to Mr. Dyer's distance, but it should be remembered that angle J is much too small to give this

[graphic]

distance correctly. I felt rather annoyed at my work not agreeing with theirs, but as they were not sailor*, they had perhaps used English miles instead d nautical, and on converting my 5,942 nautical mile, into English, it gave6,888, which agreed very well wx!i "T. B. H." and""L. M." Scarborough. W. \V. Larets.

ANIMALS AS FELLOW BOARDERS.

[101] Sin,—I beg to send you a few additional obsei vations to Mr. Van Beuedon'a highly interesting paper on "Commcusalism," which was lately reprinted in Scientific Opinion:

Is not the burrowing owl (PhoUoptynx hypog<ra) an animal which ought to be mentioned as an instance uJ couimcnMilh-m? Lu the prairies of the far West it lives iu the "villages" of the prairie-dog. \Arctosr.^%

1 udo vie in hi> ■. It is reported that even ::<-!.!■■-in...■ two abundant in these " villages," and that the quadruped, the bird, and the reptile may often be seen in harmonious juxtaposition. In the pampas of Bonth America a closely allied species IP. cunicularia) associates with another burrowing rodent, the vizcacha

/,"■■■ ■' mus trichodtictylus). (P. L. Sclater, in Nature, IL, 12; Brehm, "LUustrirtcs Thierlebcn," III.. 601,

002; .antra, Apuntam, I., 211).

I have repeatedly found Amphisbana fiave^crnt (Pr. Max.) < " Cult bra dc dot eabctas," or two-headed snake: in the nests of a species of ants called in this country "bachaco" (Attacephalotes, L.). The Amphisbsna feeds on ants, as is clearly proved by the contents of its stomach. It is, however, more than probable that the reptile and the insect are not in an exclusively hostile relation. The " bachaco" is a remarkably strong and audacious insect, a giant of the inyrinidoiiian tribe, and the number of inmates in one nest being very large, it would no doubt be an easy matter for them either to drive out or to kill the sluggish intruder. Richard Schomburgk ("Travels in British Guiana," I., 340), mentions it similar association between Atta eephalott* and another reptile, which he calls Cswaili* annulate. (Is this Cacilia lumbricoidts, Dand., or Siphonops annulate, Spix.?>

A great many insects are found in ants' nests, amongst them many bettles, either only during their larval condition, as, for instance, the roue chafer {Cetonia aurata), or during their whole life, a*' mauy brachelytra {Myrmtdoxia howMckusau Claviger f&rrolatus, Dinandra Maerkelii, M. The last two beetles are perhaps no true felloe-boarder* in the colonies of the ants, but a kind of " domesticated" animals, reared and kept by the ants on account ot certain substance* which serve as food to their hosts.

A case of true commensalism among mollusc* came not long ago to my notice. A small bivalve shell, Sphtrrium modioliforme, Anton (which, I may add en passant, is the only fresh water bivalve I have hitherto found near Caracas), lodges iu the deep umbilical cavity of the shell of an Ampullaria. It is the form called by Philipps A. crocostoma, which however appear* to be identical with the old A. ejfusa, Chem. This shell is exceedingly common in our rivulets and ponds, but though I have examined hundreds of specimens, I have found not over two dozen of shells of Sphariust. It is certainly convenient for so small an animal as this bivalve is to attach itself to a larger specie*, provided with more developed means of locomotion.

Caracas, June 16, 1870. A. Erksi.

THE AMALGAMATION MOVEMENT.

[109] Sib,—Although hitherto I have been but *. silent reader (and that merely cursorily) of your contemporary, the British and Foreign Mechanic, I cannot allow the present opportunity to pass without congratulating you, and in particular the readers of that journal, on its approaching amalgamation with "onr" Mechanic, in whose extended sphere of usefulness I am confident they will find what has hitherto been wanting in their own periodical. The Mechanic is no longer the "rough casting" it came to its present editor's hands, but is now the finished article tha' superior skill and refinement alone could make it After endeavouring in vain to enlighten the universe, your contemporary' must feel indeed highly honoured by being merged in the blaze of the English MeChanic. I for one congratulate it on the honour it has, achieved, and the pleasure it must feel in joining tie goodly company of Scientific Opinion and The Meefmi* in the world-encircling arms of our Alma Mater—the English Mechanic. The readers of the British and Foreign while, perhaps, regretting that sic transit gloria "to-day," may with renewed vigour exclaim, "To-morrow to fresh woods and pastures new!"

[ocr errors]

[10HJ Sir,—It is said that the British and Foreign Mechanic, after a troubled existence of nine or ten months, is about to terminate its not very glorious career by permitting itself to be merged in "ours." Well, I am not surprised at it; in fact, from what I have heard for some time past, I expected it would have " paled its ineffectual fires" before this. Better late than never. Thonghthe individual dies the nation lives; and though scientific journals perish individually, the English Mechanic, by some means or other, absorbs the best portions of their animating spirit. Who would have thought that your paper, with its unassuming title, would have grown so rapidly, aud attracted to itself by virtue of its central power so many of the lesser intellectual luminaries? You have, Sir, achieved a great success; von have, as Mr. Proctor says, "an enormous circulation," and you are exerting, no doubt, a salutary influence over large numbers

« ZurückWeiter »