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THK " LITTLE WONDER." IffltUtritUd on pape 2Û5.) Sir,—So much discussion has been rife lately as to the merits and demerits of Mr. Fairlle's double engine svsleni, that the reproduction of the enclosed from jZiufiueeriuff may piense many of your readers. The principal dimensions of the "Little Wonder" are ûfi follows:—

ft. in.

Diameter of cylinders 0 S~^

Stroke 11

Number of cylinder? .. .. 4
¿»stance- apart of cylinders trans-

ven-ely from ceutre to centre .. 3 1}
Length of connecting rods between,

centres 4 0

l>l и meter of wheels 2 4

Wheel base of each bogie .. .. 5 0

Distance between centies of bogles 14 1

Total wheel base 19 1

J Hstance apart of frame plates .. ' ■ '.

Diameter of boiler barrels .. .. 2 с

Length „ „ (each) .. 7 fl

Length of firebox casing .. .. 6 0
Total length of boiler between

кшоке-box tube-plates .. .. 21 0

Width of firebox casing .. .. 3 о

AVldth of inside fireboxes .. .. 2 7

Length of inside lireboxos (each} .. '■.'■'■;

Height „ , 3 0

Length of tubes 7 10

Diameter of tubes outside .. .. 0 1 i

-Number 2 18

Heating Surface.

Tube« 670 sq. f t

Firebox 60 „

730

Firegrate area 11 square ft.

Pressure of steam .. .. 1601b.persq.fn.

Capacity of tanks .. .. 90 gallons.

„ coal bunkers .. 15 cwt

"Weight of engine in working order about 19\ tons. It will be noticed on reference to the sectional plan that the firebox casing ta curved inwards at the sides, and that the two inside fireboxes are made semicircular at their adjaeent ends. The boiler shell is made of steel platee. The regulator handle Is placed on the top of the firebox casing, the two regulator valves, which are contained in the dome«, being connected, a« ahown, so that they open and cose simultaneously.

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The valve gear is of the "stationary " link type, and the motion is communicated to the valve spindles through rocking t-bafis, as eltown. The arrangement of steam and exhaust pipes will be readily understood by au inspection of the engruvlugs without special explanation,

The connection between the two boges Í-* effected In the plan adopted by Mr. Fairlio for all his later engiues, the two bogie pins being connected by a pair of side or carrier frames. In dealing with such a narrow gauge as I ft. 1 Hm . Sir. Fairlio had many difficulties toovercome; but he has shown by the performance of the "Little Wonder," that his system of double engine is eminently fitted Гпг use on narrow gauge lines, and there can be little doubt that as such Hues are more cxteuslvely constructed, the employment of the Fairlie eysteni will increase also. Admireh.

MACHINE FOU CUTTING IRREGULAR
FORMS.

SIR,—I send illustration, with description, of machine for cutting1 Irreirular forms, which has recently been patented through the Scientißc American Patent Agency Office, New York.

The main features of the device are, the attachments for holding, adjusting, nud feeding the pillars, balusters, Ac, to be cut into irregular forms or piano sides, ou a table pasta rotary cutter. The Invention may be «aid to consist of a bed, with centres, for hold! rg the blauk; one of the centres being adjustable longitudinally, and furnished with a dividing plate for adjusting the blank to the cultor, and a pattern for governing through the table of the ma h lue. A guide plate.

I, or pattern adjustably attached to the bed A, serves to direct the cutting. 1 he operator takes hold of the baltiKter at Ü, with his right band, und with his left hand on a hand rail J, puáhe* th« machine from him, and at the same tune again*t the mandrel; l,i(' machine Is then pulled or drawn back, aud lifting the spring '■airli G with the left hand, and turning the baluster with the right, one space, another side is presented to the cutting tool, thereby dressing the sides all alike, und making a thousand pieces exactly similar. After the required number have been shaped the straight bits are removed and properly shaped ones take their place, and the guide pattern is changed for one corresponding to the desired ornamental design. When this is effected, one man cau do the work of twenty men, and with greater ncatuess and accuracy than can possibly be done by hand. At the same time the hands of the operator arc perfectly safe from injury. For dreeelng stuff like the piece K. with squares at both ends, the centre pin, sceu at the end of the piece, is inserted in the hole through the centering head 11. This machine is capable of dressing not only balusters and chair, table, desk, aud couuterlegs, but can be used to dress hay-гаке and gralu-drltl spokes; and stuff that has to bo thrown away when finished by baud on account of knots and curls (the hnndsomest when finished), is dressed almost as readily as straight grained wood. J. H. T.

GLASS BURNING.

Sir,—I beg to return my sincere thanks to Mr. Jos. Leicester, for the trouble he has taken to answer my Query on "Glass Burning." The form of oven or kiln is quite correct; the iron slabs or trays that slide in the kiln are first covered with sifted whiting, and then smoothed off with what is called a sand plaue, and then the pieces of glass are laid flat on the whiting; the process of burning cau be watched by a square hole in front of the kiln, which can bo closed at pleasure. I have seen pieces of glass ¿in. or 3tu. long and Jin. wide, with the flux painted on, and bid on one of the slabs, aud called tests; tbey are taken out, tried, and by thera may bo known wheu the glass is sufficiently burnt.

The letter to the Editor, In answer to me, describes the silver melted iu a crucible, and autlmouy as a flux, but did not eay whether they are to be melted together or in what proportions; if the writer wuuM kindly say something upon the subject through the medium of the Mechanic, it will gieatly oblige me, and perhaps many others. Gusta Va Knox.

DARK LINKS IN THE SrECTRUM.

Sir,—Iu reply to your observations on my letter, p. 183, I beg to observe I did not state my Inability to give any evidence at all to Mr. 1'roctor. as that would not be true, but the spectroscopic evidence required from me In the letter ou p. 130. 1 have, however, no objectlou to give reasons for considering the darx lines in the solar spectrum entire!) atmospheric. When Bunten antí KirchhoíT arrived at the conclusion that the dark lines were of solar origin, they considered the sun an incandescent body surrounded by а luminous atmosphere; but later researches represent It as a non.luminous globe, surrounded by matter In a Plate of Intense chemical action. If this is correct, the only foundation for the supposition of the dark lines beiug solar Is the great depth of the photosphere and the outer ami less luminous envelope absorbing certain of the rays emitted by the inner und brightor portion. Before adopting this hypothesis, would it not be well to ascertain wnether the earth Is not also enveloped by matter capable also of a similar, though le-* Intense, chemical action? I apprehend there is sufficient proof that euch is the" fact; aud if во, the origin of dark lines in the spectrum of any luminous body outälde tho earth's atmosphere is uumistakeable. T. A.

by bringing each place to the brazen meridian,and then noticiug the figures on the equator, we can obtain the difference of time, and vice versa Longitude may be converted into time by dividing by 1Д. aud reckoning each degree over as four minutes; and time may be converted into longitude, as every sailor knows, and hence vessels take out chronometers with them for this purpose. To convert time into longitude we must multiply each hour by 15, and reckon every four minutes over as one degree. The difference in longitude gives rise to other differences, as peria-ci, anta-cl, and antipodes. The perixci, for Inetance, are those who live in opposite longitudes, but In the earns latitude. By noticing the etymology of the word fftpt around, and оисш to dwell, we shall the better comprehend iu meaning; thus In tho figure, suppose wo lived at В ou the globe, our periœcl would live at A. just 180° away from us, aud nothing can show men clearly than this, that the earth is round, and tur» on its axis, for Inconsequence of doing so, when it U 12 o'clock at noon at B, it is IS o'clock at night at A. and vice versa, but since all In the same latitude must have an equal share of the sun's rays durinn the day, the length of the day to the one is the length of night to the other, and of course the eeasonstoeach of these must be the same, for all those in the same latitude have winter at the same time, as well as the other seasons. The antaeel, however, derived from arri, opposite to, and оисш to dwell, are those who live in the same longitude but in opposite latitudes: that Is, the people who live at E. have their anuref at F, and tho autael to N are those, supposing there ore any, who live at S-, and the antffci to 23e N. latitude, are those living at %ifl S. latitude, and the consequence I», that their time Is exactly the same, but thefengthof the day to the one. forms the length of the night to tbe other ; that is, if E has two months' day, Y has two months' night at the same time, but their seasons are opposite, tecause they live in opposite hemispheres, and wheu Boreas, bringing snows, reigns in one, the mild breezes of summer blow in the other. But again, if people live in opposite latitudes and longitudes, they are called antipodes, from am opposite to, and. 7T0vçt the foot, because their feet are opposite to ours,

READINGS FROM THE GLOBES.

Sir,—It may not be out of place ut tho present tim « when some of your subscribers are ioquiriug about globes and longitude, to offer a few remarks (addressed chiefly to juuiors), on the uses of those Instructive instruments. The proofs of the roiundity and motions of tho earth which have been lately given In these columns by Mr. Proctor, have show» that the earth is of a globular form, aud the phenomena which tho globes illustrate, rest upon this supposition, and cau be accounted for en*llv ou this principle, for if the earth were not round, the time would of course bo tho same in all parts of tbe world at the ssme time, nud we Should have no difference in longitude. Different couutries take different meridians, us the line from whleb to reckon longitude; generally speaking, tbo capitals of their own country, whilst England reckons her longitude from Greenwich Observatory; hence, if we wish to know the difference of time or longitude between two places, we have only to ascertain the longitude of each, which, supposing the. globes are accurate, is aVery simple process, and then subtract them, if they are of the same name, but add them 11 one is cast longitude and the other west longitude. As the globe turns on Its axis from west to east, those Wh* live in west longitude must have their time earlier than those liviug iu east longitude, because they will not come Into the enlightened hemisphere so soon, Having, then, ascertained the difference of longitude

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and as tho sun, owing to the rotundity of the earth. can only shine over half the globe at once. It is night with our antipodes when it is day with us ; and If their m miners and customs arc the same, when they are enjoying

41 Tired nature's sweet restorer, balmy sleep," we are busy at our several duties, either iu work, business, the counting-house, or the Stock Exchange; and the seasons are also different This interesting subject might be carried farther, and although elementary truths, familiar to the astronomer and geographer, they might still prove of service to some whose pursuits prevent them fiom consulting and studying larger treatises. Should you deem these few remarks worthy of a placo in your periodical, I will follow them up with more observations upon the same subject.

THE SAXTAIKE LATHE.

Sin,—I received your last monthly number only s few days ngo, and to my great surprise saw on page 52, au illustration of Titus Salt, Efq.'s, latho, as it was published without my knowledge or consent

In November last Mr. Northcote wrote to me re

? Mating the loan of the drawings of Mr. Salts latho, or tho purpose of publishing them, together with a description of the working of the lathe, &c. Mr. Northcote being a perfect stranger to me, 1 answered that I had a decided objection te do so, unless It was done efficiently, with details, and a full description, accompanied with specimens of work produced by means of tho different parts of the lathe aud apparatus, and I added that 1 thought it could ouly bo done in a separate publication, and that I should require some time to put it together, so as to render it intelligible and useful to amateurs aud others; these conditions did not meet Mr. N.'s views, and there ended the matter.

I afterwards read a letter from Mr. Evans to the Mechanic, in which he says that the lathe beiongiujr to Mr. Salt was almost exclusively made at Aw factory, tho outline* ai the designs having beeu prepared by Mr. Smith*, of Jersey. Jsow, 1 beg to state, the moas

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May 20, 1870.]

ENGLISH MECHANIC AND MIRROR OP SCIENCE.

209

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part of the lathe was made at Saltalre. Mr. Salt, having decided to bare the lathe finished in London, went to Mr. Evan«, and referred him to me. I give you a copy oí Mr. Evans' letter to me :—

"Loodon, Feb. 24.1866.

"101, Wardour-strect. Soho.

ы Sir,—Some davs ago I had the honour of a visit to Saltalre. to consult w'tu Tir Ih Salt, Jun., Esq . rc-f ■ ■'(>- the making and completing his lathe, which lie had begun under your directions ; we Inspected all the drawings you had sent him, and 1 was put in pos. ■ ...ir. of your ideas upon the several motions and яр* plications tobe attached thereto, and he hss forwarded the lathe to town ; he has suggested also that it would V advisable lor me to pay you n visit to con-ult with * ■ 'i. which I purpose doing with your kind permission.

*' Since the receipt of the lathe I have received a letter from Mr. Salt, wherein he mentions that without an understand]!];; with me that your ideas should he kept private you are not disposed to give the beuefit oí your experience.

1 Now, Sir, 1 trust I shall be able to entirely remove any scruple you may have in the matter. I have been engaged for many years in the making of models and machinery, aud carrying out the ideas of inventors and gentlemen amateurs ; and I will undertake thatmo orignal idea ot yours shall be made public or manufactured without your permission first had and obtained. I hope aud trust you will not hare any doubt on the subject, but permit me the honour of waiting tinon yon at your residence, so that I may have the benefit of a personal interview. From your drawings and particulars given in detail, your experience must be mature, and of great value. 1 hope to have the honour of a reply, staling when it will suit your convenience to receive me.—I have the honour to be. Sir, your most obedient servant, W. J. Evans.

"To John Smith, Esq., Jersey."

Now, la presence of sueh assurances, t wrote to say I was ready to receive him. lie came over to Jersey; I showed biin my own lathe, and all the apparatus (my own work, and the result of many years1 experience); he had all the Information that was necessary; ho noted all the details, and made many sketches and memoranda ; I afterwards sent him many drawings details, and the whole of the work was carried out under my supervision; I vielted London mtnv times tor that purpose, and U waa with great difficulty I got the lathe as complete as it is now, having been obliged to order many parts to be cast aside aud replaced by other«, according to my original design.

I also took Mr. K. to sec a lathe that I had made for a friend of mine in Jersey, the same tn nearly every point aa Mr. Salt's. Now, Sir, I think this is rather more than mere outlines.

On page 88, yonr correspondent 'J. K. P.," says :— "• I happen to know that a great part of the lathe which was made at Saltalre, and which came to Mr Kvans', 102. Wardour-street, to be finished, was put on one side, and entirely remade " ; this statement Is not true.

I am not aware that the slide rest hai any steel vtbeel*: the saddle has.

"J. K. P." hopes that bis (Mr. K.'s) mind is not oppressed wiih the recollection of having made for such a lathe such a chuck as the face plate with four doge sticking out nflt. which is shown on the floor in the picture. Allow me. Sir. to tell "J. K. P." that the ehuck was not mine, nor made with my consent or knowledge.

On page 114, "J. K.P." again states that there are several small wheels In thesliderest. I am not awur» thin there are either wheels or rack. The saddle was from my design ; the slide rest was not what I wished to have made, but very different, aud on Mr. Evacs' plan.

Now, Sir. I will put a question to "J. К P." How came he to kuow all this In presence oi Mr. E.'s engagement not to show the lathe, or make it public? Either Mr. K. must have forgotten his promise, or " J. К P.'a" letters are manufactured at Ш, Wardourstreet- John Smith, St. Hellers, Jersey.

[Most assuredly our readers have heard enough about the designer and iuventor of this lathe.]

COMMERCE AND TEADE. Sir,—Questions in political economy are, I fear, hardly suited to your columns. To admit the discussion of them would be like the "letting in of water." The deduction I should draw—briefly stated—from " s. Kymea's" statisticsotthe trade of the United Kingdom for the year 1808. is, that for £171)000.000 of exports, we manas-ed to purchase £291,000,000 of imports; a profitable year's bueineas, surely. 1 hayo no doubt, however, that there was a considerable export of gold, of which no mentfou is made iu the statistics given, and without which no conclusion enn be arrived at as to the net results of the commercial transactions of that year. Exchange.

TOOL HOLDER. Sir,—The enclosed rude pencil-sketch represents a tool-holder or simple slide-rest which I have constructed. It will be found useful to amateurs in the absence of a regular one. I think the followiue description will explain it:—A lathe shears; В socket or holder, which can be adjusted to the shears in any position by the nut С; D frame of slide-rest, forged out of malleable Iron, fin. by ljtu.; E slider made of Iron tubing, with a square flange soldered to the underside, which slides in grooves or key-seats in the eyes V F; G tlio screw upon which the slider trar«de, aad which can be brought to bear upon the work ».,,'i vhe requisite pressure by turning the handle II.: í I tw<y-p4ijwhlng screws, which can be pressed jrenlly against the ¡(¡Юре1, surface of tlio slider, so as to prevent vibration w„»*le at work; К the cutter, which in held In "pos/tlm, ь cutter.

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This little ellde-rest is particularly adapted to work to be turned on the face-plate, such as small cylinder covers, fee., where ornamentation by beading or grooving is required. As a kind of clroular motion may be given by turning the slide-rest on its shank It, all kinds of OG patterns similar to the handle may bo turned by feeding with screw G. Of courso the holder must be bored out true, and the shank turned down to a good fit, In order to ensure stability and freedom from vibration; and when required to be rigid, It can be held quite tight by the screw P I have done several Jobs with it, and 1 And It a great improvement on the hand-tool system, as it permits the operator to tur« the lathe for himself.

I don't know whether this Idea is orliiual or not but I assure you it is quite new to me.

Christoi-heb. Fallon, Barthgato-by-Edlnburgh.

THE REPUTED FIGURE AND MOTIONS OF

THE EARTH.-THE EARTH'S ROTATION.

{Third and concluding Letter.)

Sir,—I shall have occasion again to revert to the

optical deception I noticed in my last when I come to

consider the question of " Parallax." and will not now

say anything further on the measure of a degree

except just to notice that if we take anything short of

the true diameter of the circle as the base, thedlvlsiou

of less than one-half of that circle into Iko parts is au

error, aad that the arguments adduced by Mr. Proctor

in his fourth chapter on iho " Determining the Shape

of tho Earth," are consequently equally erroneous.

I have noticed Mr, Proctor's arguments on the

Diurnal Motion of the Sun and Stars," and also his

admission with reference to tho system advocated by

Tycho Brabe, which, toa great extent, renders further

reply on my part superfluous, I shall therefore at once

examine his argument« on the gyro »cope aud peudulum

experiments, in proof of the earth's rotation.

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Suppose weset a peudulum swinging due north and south in a carriage running due south, and suppose the horses' heads are all at once turned to tho west. Is there auythlug woudertul in the pendulum (freely suspended) still continuing to osclllute due north aud south? Would not the force caused by the falling weight be still in the ваши direction, nlthough the direction of the course pursued by the carriage be changed 50 times? Such direction of such force would be the same, and the greater wonder would be if it were not so.

But how does this argument fit when examined fairly? If we are really pussiug from West to east at the rate of nearly 1500 feet lu a second of time, how comes a peudulum, set swinging due east and west to continue to du so? Would not surh a speed cause a greater impulse to be imparted to it one way than tho other? As we must bear in mind that the point of suspension is attached to the supposed rotating body, aud also with a string from a suspcuslou of 17ft. Din., us in the experiment noted.

When the peudulum wits at the limit of its swing to the east, the support will have passed nearly 1500ft. it, far less time thau the pendulum swing will complete tho proper arc of a circle В С (Fig. 1). For Instance, let W E be the direction of the earth's rotatiun, as shown by tho arrow, then supposing the pendulum bob is at B, the support will have passed nearly 1500ft. towards E in far /es.« tiiw thau It will take the said bob to reach С We will suppose, for tho sake of easy illustration, that the pendulum makes one ewlug from В to С In a second of time, how is it possible for it ever to reach D, to say nothing of lis reaching C, when we iiud that tho support itself has travelled more thau 80 times as far as the length of the peudulum during the time taken by one motion of _he same?

But we will further suppose the pendulum to be set swinging due north and south, ana the earth rotates from west to east, how are we to account for this great speed not interfering with the oscillations of the same? us the current of motion will not directly across the piano of its oscillatiou, and, as a mutter of course, would materially interfere with its so-culled gravity, and niter its course to the west nul not to the east, out of all proportion to anything noted lu the experiments adduced by Mr. Proctor.

I am aware that it is said that the pendulum experimente prove that tho alteration in the plane of oscillation, proves that the earth rotates about an a*'"' causing our day and night; that If a pendulum could be adjusted nt one ot the poles, or at the equator, the oscillation would continue true, and that because we are situated midway between these two points of the earth's surface, this alteration iu tho plane of oscillation Is attributed to tho earth's moving from west to east; but, as I have before shown, it Is impossible between our position and the equator.

I now ask, would it not be strange (putting aside the question of rotation altogether) if a peudulum. suchas Mr. Worms mado use of, did not vary in its oscillations place it where he will, with a ball of brass 401b., and a steel wire 17ft. flin. long, both liable to magnetic Influence. The greatest wonder Is that we And men so wedded to theory as to apparently overlook perhaps tho most Important aad least understood principle in nature, and by silence disclaim, as it were, the existence of such a force and principle as terrestrial magnotlsln—a force continually changing both in direction aud power—a principle whose source and mode of action our best philosophers cannot explain.

Tho gyroscope Is but another repetition of that force aud direction of motion we "we seen depicted by tho pendulum experiment. \ о ever imagined that if any AIM or wheel, for instauci -as Hnnly fixed toan axle, and free to rotate upou H '.hat it would not do so. If sufficient force were given it? And wo know well where force is applied to we. ht, and this moves In a given direction, force must t applied to alter that direction, or it would continue . more iu tho same course until such force is spent. » is when a combination of forces and motions arc calkd forth, which renders the matter aomewhat perplexing, as the gyroscope, for instance. But to treat of this principle fully would occupy a volume itself, end caunot, therefore, be satisfactorily treated hore, but I may just say. when the action of the gyroscope comes to be fully understood, and worked out in detail, our present dynamical theories will not only be found wofully Incomplete, but erroneous also.

If this experimental gyroscope had been placed on a rapidly rotating sphere, which is the only way in which the experiment can be fairly tried, would it "travel against" the sphere in rapid rotation I I maintain that it will not. Suppose the direction of the earth's rotation is from west to cast, and that the speed Is after the rnto of 17 miles per minute, and lot the line of motion be perfectly straight, for the sake of simplicity, what Instrument, supported on a " pointed pivot," could remain true for an instant, or witbetana the directive force of such a motion?

But how is It that this instrument gives the вате result relatively, no matter In what direction It is put into action. If its motion is "against the direction of the earth's rotation?" How is It that It oan travel at all iu other positions wllh euch an enormous speed to overcome, especially when we consider the great nicety, and such slender connection through its supporte that it has with the earth?

Again, there must be continual application of power if tho motion of a gyroscope is to be of long duration, otherwise tho disc will cease to act. Here, then, two questions present themselves:. 1st, Does the continued application of power tend to alter the direction of the axis of the disc; and 2nd, Doos not the influence of motion by a species of centrlpetnl force give the results as seen? It Is plain it Is more owing to tho unexplained laws of mollou than to the earth s rotation.

1 come now to consider the other reasons given by Mr. Proctor iu support of tho assumption that the earth is globular, aud, therefore, that it rotates about its axis. He remarks that the "sailor voyaeing lu the southern seas, estimates Ыв progress strictly according to those results which follow from the globe fliuroof the earth," when the вку is clouded. 1 may ask, Is there anything remarkable In his being able to accomplish this, with proper means and appliances at his disposal? Ho knows by the chart tho relative position of one country or island to another, aud whether he goee lu a straight line, or straight round, it really matters not, so that his position is' clearly known and the relative distances correctly recorded. The greater wonder would be If he could not do во.

The fact that the "upper masts of a vessel " outward bound "may be out of focus when the sea horizon is brought into focus" is fully explained in my remarks on Fig. 3. In my last lctter(ENOLisn MechaNic, page 135), and has simply refereuce to the limit of vision as the observer's horizon. But In order to show clcariy that tho lines of vision generally appear curved, we must examine their bearing iu reference to distance. I Bay "generally," because there is on record extraordinary peculiarities in some people's power of vision (see Dr. Ussher's papers on " The Eye. ;md Something About It," Enolish Mechanic, Vol. X.. page 296). The man in the Mauritius who "was «bio to anuouncc the approach of vessels days before they arrived " had a peculiar power of vision, wliicb, во rar from being general, is entirely exceptional, and the fact of our gifted author recording this, In keeping with hie extensivo knowledge ol the organs of viaiou, point clearly to the саш*о proceeding from th3 peculiar formation of the human eye. 1 am afraid I mav have done wrong In alluding to Dr. Ussher's admirable paper in support of my position, but I, at tho same timo, hope Mr. Proctor will not sharpen his ironical sword for use upon him. I cannot realst a smile when I ask Mr. Proctor If the man, when ho announced the approach of these vessels (when ne other eye could see them), saw through the ocean, which he must do if the surface is really convex.

It is not necessary that X should enter at length into " the shape of too earth's shadow as seen during a lunar eclipse." Knough has been acknowledged by Mr. Proctor on page 242. Vol. X., of the English Mechanic to cast a doubt Or the minds of moat man as to the correctness of the present theories, especially when we find it acknowledged by our author that " uothing but the complete survey " (described in Chapter IV. of his papers) "can be held to be a satisfactory proof." When that shall be shown to fail, what is to become of our boasted system of modern astronomy?

The "peculiarity noticed by balloonists" Is accounted for by natural laws. When he ascends from the ground the earth gradually assumes more of a concave shape, until it has tho appearance of a huge 'basin. If he looks down upon the earth below him, the rays oí vision pass perpendicularly through the atmoephere; but if he casts a look at the distant horizon, at С or D, the rays of vision are bent towards the perpendicular; while if he looks upwards luto a rarer atmosphere, the sky assumes a convex appearance, as tho rays are bent (looking towards С or D) from the perpendicular, А В. In short, many «f our theories are based upon wrong conclusions, which the plainest principles of vision will illuetrato and explain.

I have now brought my remarks on the Earth's Rotation to a closo. I might have adduced other arguments in favour of my posltiou, but I think I have produced sufficient to induce serious thought on a matter too much conüued within the sphere of dogmatic teaching. John Bkardslev.

[At the foot of Mr. Beardsley's last letter we offered an apology for inserting It; now we must say a word or two in explanation. Almost Immediately after the appearance of Mr. Proctor's admirable series of articles on the Karth. we received a letter from Mr. Beardelcy, saying that he was preparing, in a series of lottere, an answer to Mr. Proctor, and asking us whether we would insert it. Believing in free discussi >n, and believing also, from the tene of Mr. Beardsley's letter, that he hr.d something worth saying, we said "Yes." Having given a promise, we felt bound to redeem It; but we must say that hnd wo any notion at the timo of the probable character and quality of Mr. Beardsley's reply, we should not have consented to allow him space. Possibly, however, the insertion of the letters will do good, as thoy show on what a narrow and ehaky basis the theory of the earth b olng a plane rests upon.—Ed. F.tf.J

dncod. Another most interesting fact ki connection with my theory is this:—This axial motiou tnking place in a direction contrary to that of the orbital motiou, not only produces tho changes of the* seasons, but ulsn maintains the parallelism oithe axis of diurnal rotation, the poles of which always point in a particular directiou. Now, supposing it had pleased the Great Architect of the Uuiverse that tais motion should have been in the same direction as tho orbital one, we should still have had the change of the seasons; but would the axis have maintained its parallelism? No. Instead of our polo being constantly directed toward» Polaris, it would during the year make two complet* circuits of the heavens. ThU proposition 1 believe I am in a position te demonstrate to be n fact, and I shnll be most happy to discuss the question with some oi your able astrouomical eorrespoudents, so that it may receive a thorough Investigation. F. F. Henbest.

THE MOTIONS OF THE MOON AND EARTH.

Sis,—Will you allow mo a small space to give my views respecting the motions of the earth and moon, oe they differ in one or two particulars from the gencrally-roaeíved system of astronomy? About the year 1854 1 felt a wish to construct a machine which should truthfully represent the motions of the earth, more particularly with reference to the changes of the seasons. In considering the eubject with this view, the conviction forced itself upou me that the earth has a third motiou not taken into account by astronomers— namely, an annual rotatory motion on an axis perpendicular to the plane of its orbit, and on the same principle that the moon has no axial motion. I am aware that a controversy on this question was carried on in the public papors some short time after I tlrst propounded my theory, but I never got a sight of any of the correspondence; thorefore, I am entirely Ignorant of the nature of the arguments employed either pro or ron.; so that my ideas are entirely original, so far as I am aware. The new theory, as discussed at that timo, I believe, had reference only to the case of the moon. The principle of my thoory Involves коте very Interesting ana important results as regard* the earth, and which are well worthy a thorough investigation. But to the point. Astronomers tell us that the fact of the moon always presenting the same face to the earth proves that she turns on her axis in the same period of time that she performs her revolution round the earth. I maintain that this fact proves the contrary; for if the moon turned on its axis as described, each hemisphere would be successively presented to the earth. The phenomena presented by the moon are entirely the results of its orbital motion In conjunction with its annual journey round the nun. I will give ono illustration of my view. Suppose a ball fixed to one extremity of a rod, the other being held in a person's hand, the arm and rod being maintained in a horizontal direction, the person turns round, carrying the rod and ball with him. Tho ball makes a revolution round the person, and while tho some hemisphere is constantly turned towards the person, it Is successively presented to each point of the coBipass. The ball has a motion about a centre; but where le that centre? Not within itself; it cannot turn about its own axis in the way supposed without boing detached from tho rod. Tho ceutre of motion is the person holding the rod, about which the rod and ball turn a- a common centre, and producing precisely similar results to those produced by the moon/s revolution round the earth.

I will now endeavour to state my views respecting the motion of the earth. In order to produce the changes of the seasons, 1 maintain that It is necessary to suppose я third motion, such as I have described in connection with the annual journey of the earth round the sun. And here a most, Interesting fact presents itself. By supposing a slight discrepancy in the période of the orbital and the axial motion that I contend for, tho precession of the equinoxes is pro

ON VELOCIPEDE CONSTRUCTION.

Sirt,—From the number of queries contained In your journal, it is evident that subscribers are continually making tbelr own machines—some from one idea and some from another. In many instances these now desigus prove a fail uro because of the puff which announced their birth. The" Edinburgh" velocipede was advertised as having run four miles in' 15 minutes. It might do that down-hill. On the road from Macclesfield to nuxton there le u gradual ascent of nearly six miles, and then it is я rapid five miles down-hill. The latter part of the journey might be accomplished in 18 minutes; but suppose you were only going seven miles an hour, and ran against a brick end left in the road which had been used by some carter to rest his horso with, why there would be a shock, aud at the more rapid rate there might be a tipple. The inventor of the velocifere had better have one made (at his own expeusc) before coaxing any subscribers to your paper to make one themselves, and no doubt many gentlemen would be glad to witnos* the 15 miles an hour run so easily, lam not at all surprised at Query No. 2ГЛ0 befntr in a fix with hi* ratchet, pawl, pulley, spring, &c. Depend upon it, the more simple these machines are constructed, the better they will go.

In answer to Query 2Ö78, the "High Peak" velocipede is a moderately good travelling machine on the level and down hill. So are all three-wheelers where you drive from the crank under the seat, and steer from the frout wheel, on condition that the machine is not over 701b.; but, mind you, It is work going up bill. I have ridden the three-wheeler with tho movement reversed—that le, I steered from behind, like a boat. This machine went splendidly up hill aud on the level, but was dangerous down hill, because it tippled you out like я load of bricks. I have also gone out on the "Macclesfield" velocipede and the "Engllsh"veloclpede, both of which Яге very useful and agreeable -, easy to work up hill as well as down—in fact, 1 and a friend ran в mile-and-three-quarters, all up hill, the other day, in 10 minutes; but I prefer taking my time.

I don't believe In the bicycle movement, because the knee has to describo a circle, whereas the legs simply rock to and fro In the velocipede, which is less fatiguing. Watch a child seated ou a form at school rocking Its legs all day without any apparent trouble. 1 hope that all the subscribers now making their machines will look to simplicity of mechanism, and try to save weight and friction, which they will find to their advantage.. A Stringer.

HYGIENE OF VENTILATION.

Sir,—Many plans for effecting this desirable object have been carried out, both in public as well as in prlvats buildings, aud many more proposed, but all have, more or lews, met with objections on various accounts, with tho sole exception, I believe, of the Silvester system, adopted in the infirmary at Derby. The method proposed and published by me some years since, for the ventilation of phosphorus match manufactories, is »imple in its character, and If properly carried out, would scarcely meet with objectors, and is quite Independent of doors and windows. The principle is to cause the vitiated air to pass out through the floor, and the fresh to euter through a flue pierced ceiliug in the following manner, namely. From the space between the floor and the ceiling below, lead off a tube or truuk iuto a chimney or air shaft, rising above the roof, capped with a directacting cowl, that is to say, mouth from tike wind. In a similar manner lead off a flue from the space between the celling and the floor above, iuto another chimney or air shaft, capped with a reverse acting cowl, mouth to the wind.

In order to obtain a fine pierced ceiling, all wo have to do is to leave out all the plastering on the laths, which in this caso should be sawn, not split, and set close. Sawn laths would present an even surface for colouring In distemper, or other ornamentation. The pierced floor is produced by laying down a border of fine pierced thin metal, of sufficient breadth for the size of the room. If the automatic actiou of the atmosphère should be deemed Inadequate to perform the office of perfect Ventilation, a small stove may he placed somewhere in the upcast shaft, as is usual in our collieries. In more important cases, it may be advisable to adopt exhausting apparatus, set in motion by steam. tr*s, or water pressure, as in the present mode of blowing largo organs; and it muy be observed at the same time, that the friction of rarefied air in the exhausting process, is greatly less than that of с »in pressed air ш the blowing tubes, as proved by the fact that after a certaiu length, the most powerful blast will fail to put out a candle at the farther end, but by exhaustion it is immediately extinguished at the same distance.

There is an obstacle to the Introduction of this mode of veutilutlon, that It cannot be the subject of a patent right, and therefore It is not very likely that it will ever be brought to bear. The products of the combustion of gas, or other lights, should always be corned off independently of ventilation by any mode by the arrangement perfected by the laic Professor Faraday.

Henry W. Reveley, Readlug.

CHOOSING ONE'S BELIEF. SiR,—In the current number of our journal is A letter from " Saul Kyrae* "on the rotation of tho earth A-c, which, though нп admirable lettorin most respect*», со n ta i ue one statement whieh is decidedly wroug; be talks about people choosing their belief, now it it» impossible for any man to choose bis belief; for instance, just let "Saul Rvmea" try to believe, say Im» lmlí-an-hour, in the theories of "Parallax," John Hampden, or any #f that fraternity, and be will see tho impossibility of any one chooeitig bis belief. There are many things which I should like to believe, but I cannot do so, the evidence Is too strong the other way. I do not believe the earth to be fiat like a pancake, but it is not from a wish to believe it globular, or rather spheroidal. I can no more doubt the form of the earth than I can doubt that the sun will rise to-morrow morning, and this is the case with everything else, from the greatest to the smallest. We must believe according to the evidonce presented to our senses, and not according to our own wishes or choice.

T. Cooke.

ASTRONOMICAL.

Sir,—I thank " Omicron " for the explanation given as to the formula respecting the brilliancy of Venus. If he had time i could wish him to Insert anew the formula given at page 61 i. Vol. X. for finding the longi* tude and latitude ofa heavenly body from ita right ascension and declination, it being impossible 1« young astronomers to make anything of it o-s tum printed. Of course I amulittle versed in these things or 1 should have been puzxled with it too.

G. FjRTfi.

QUADRATICS REDUCIBLE TO QUADRATICS

{Continued /ran page 131.)

Sir,—" Bernardin" is correct in his supposition, but I intend simply going the shortest way to work in order toget the answers given by Mr, Todhouter. I think without egotism that I may say the solution

given by me is similar to that which woald be given y Mr. Tod h outer himself, or I greatly mistake his letterpress upou the subject. But

(7. ) x + 2 *J (a x) + с = 0

[table]

V x*

I should bo glad tf " Bernardin " would explain why such examples a» the above aro Inserted. Llfco "Uiinol," 1 do not for the lile of me see their utility. Asa tutor I k;iow pupils hate aud deteet the bight ol abstract questions containing the п'* or any powers not expressed by arithmetical numbers. I scarcely soo the us'.-, therefore, of giving solutions to such questions, but to such as wish it the ubove may he solved by multiplying by 3 V *«. *h®u dividing by » and working as a quadratic. Unlike "Gitnel." 1 believe a'gebra is extremely useful, as, in some futuro numbers, i will endeavour to show.

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much, Ьш'пем having to be brought on, I did uot gee an introduction. Had I beca able to hare finished it in time 1 should hare put it into the Exhibition of July next. John L. Hawkins.

SILVERING GLASS SPECULA. Sib,—In reply to letter by Mr. James Gray, at p. Mti.l beg to inform him thnt iu silvering by the tirthelle salt plan, I found a marked improvement by impending the glass in the liquor instead of covering tbe glass with it. 1 found in the latter way that a LbJrkllltn formed ou the upper surface of the pool of liquor, and this seemed to keep the light from the ssrisce of the glass, and stop the action there, but vbea the speculum wad reversed and hung as in Browning's method, the sun shone strongly through tbe glaes; and by this means several very decent films hâve been obtained.

With respect to hie query about the size of small mirror, if the question In not undeserving of a formula, 1 beg to send the following :— Let A = tbe apertareof speculum f = its focal length

a = aperture of field lens (lowest power) •/ = tbe distance the image is thrown out from the axis of telescope

x = minor axis of small mirror Then

Л (A - a)

x = + a

r

And if In his case w* suppose the dlsmeter of tbe fleld lens fin., and the image thrown out 7in., wo have

7 (4 - Î)

x + | = IJln. nearly.

llis mirror must not be less than this; be bad better a« one liba. A. J. Thomas.

TO B. A. PROCTOR, ESQ.

Sin,—I am only a most unfortunate lover of science, and, as such. 1 most earnestly endeavour to keep myself apace with what appears in the scientific world, as much as I possiblycan. Of course, I read your very able productions, both in English and French periodicals, and mainly in the Kñclish Mechanic. Not knowing your personal address, I venture to write to you through the median of the latter most valuable paper, in the hope that these, my lines, will reach you. Being French, I beg you make allowance for my incorrect Ian guace.

Home time since I was struck in reading in a French review a lew words on your new theory of the milky way. As it was but an abstract, 1 could not make couch of it, aud could guess nothing as to the principle oud law upon which it stands; but I remained convinced that you are not acquainted with the physical law applicable to this great sidereal circle and Its mode of formation, as when tbe law of a phenomenon in known all theories respecting it are at an end. I hope it will not be trespassing on polt renes s and personal respect and consideration to humbly tell you that such a law, such a mode of formation, are known, have been printed and published now for several years, and that, for i ne. at least, they do away with all uncertainty respecting the real nature of the galaxy, its form, composition, rules, Ac, and its absolute mathematical connection with tbe universal sidereal system. The publication of the great work in which the details are containod was begun In 1858—12 years ajro—but the part of it specially relating to celestial bodies and the galaxy, appeared in I860, under the title "Physique Céleste;" it consists of about 300 pp. fcvo., forming 3 volumes. When at Exeter, nt the meeting of the British Association, in August last, 1 had the pleasure to present a copy of it to Mr. N. Lockyer. Since thisl sentone to Mr. Warren-Dclarue, and/should very much like to know the opinion of these savants upon works affecting so high a pretention.

In another number of the ваше French periodical I found, as translated from you, a '*Jl<;molre préliminaire sur certaine mouvements de translation dea vtoiles." This being moro extensive, can fix ones mind upon its purport. After having read it, I feel convinced that you are yet seeking after a centre round which all the other sidereal bodies gravitate—a thing, again, that, unknown to you, no doubt, has been determined, printed, aud published, long ago. In IS67 I took the liberty of sending to Mr. Glaistier, with a letter, a copy of a pamphlet entitled "Le Grand Soleil visible au centre du Système du Monde." with a celestial map representing the galaxy, with all the constellations, «fee, and showing the universe is different aspects, according to physical laws г of course expected from Mr. (¿laisber what I never failed to obtain from English gentlemen—that is, nt least an acknowledgment of the compliment paid him in my letter, and ahm of the receipt of the pamphlet. I wa* deceived in my expectation. Mr. Glalsher remained lilent—which was very easy. I send with this letter one "f these pamphlets, with a rough sketch (I cannot draw) of the celestial map, for your perusal.

Now will you allow me to present a few remarks upon your " Mémoires," from which i will moke some quotations in French, as I do not possess the Kuglish text? You ore made to say:—" J'ai trouvé que dans certaines parties du ciel. les étoiles manifestent une tendance bien inarquée à si mouvais suivant une direction déterminée." May X be allowed to say, thnt many years ago, the very celebrated \V. Herechel had oh Nerved it, not as a tendency, but ns a fact; and that this great man for a long time KoiiLrht for a central sun, which he considered as existing, our own sun having an orbituarv motion round it? Later, Argelander made researches, but ata distance so far ач Ihiv from its real placo, lio could not Und It, and Whs then contradicted by J. Herechel, who was in the right ; but a*ht* father had attributed the movement or tbe bright stare to thul of the «un, he dared not go fart l) er.

"On ne pent quo regarder comme trê4 significatif to fait que dans une grande partie du ciel il doity avoir un mouvement commun, tel quo jo l'ai Indiqué. Jl i

me semble qu'on est force de considérer les étoiles qui présentent an mouvement commun de cette nature comme formant an système distinct dont les membres sont, il est vrai, associés au système de la voie lactée, mais qui sont plus liés entree eux."

What you say you bave indicated is precisely what was first suggested years ago by Sir W. Herechel, and, as 1 said before, was actually discovered and published iu Fiance several years ago; therefore it is not а novelty.

"J'ai ¿té amené íl remarquer que lo gronpe nombreux d'étoiles autour di y de Peraee *i trouve presque exactement à l'intersection de la vole lactée et du grand cercle qu'on peut appeler l'équateur du mouvement solaire, ceet-à-dire, du grand cercle qui a pour pole le point vers lequel se dirige le soleil. Cette circonstance pourrait faire regarder ce groupe, plu« qui celui des pléiades, comme le centre du système sideral, si ce système avait un centre que nous puis -ми reconnoitre." Certainly the sidereal system bas a centre, and not only we can, but we do know it, and \cf can, see it with naked eyes; but it Is not in the direction of iç of Persee, which, relatively to our sun, Is almost in the same direction as the Pleiades. The Hyades would be nearer still, as the real place is in the direction of the neck of the unicorn.

I do not think it necessary to enter into any more detail.- on the subject, and beg respectfully to refer you to the annexed vouchers.

How fortunate you are in England! Whoever has a new Idea or conception upon any hitherto unexplained subject is sure to find a press ready to make it public —nay, to take up matters зо as to set forth any parcel of truth It may contain, and discussion never falls to auyonc. Not so In France, 1 am sorry to say. Money is the only god now worshipped. No Editor will publish anything, however valuable, unless he is largely paid for it; and even nnder such conditions, if the new Idea Is likely to disagree with ДГ.А.'в or M.U.'s theories, as these autorités savantes ordinarily bring water to the mill, there is no hope of our obtaining auythiug like publicity, were it for a Newtonian discovery. No one can form an idea of the check that science receives in France from the extinguishing power of esprit de corps and journalism. It we are now so far behind other nations, this is one of the principal cause». I tried to contend against such a regrettable state of things iu creating the Réforme Scientifique, of which I here send a few numbers for your inspection, but I was not sufficiently supported. A thing worth mentioning, and for which I am grateful, is that English subscribers were my best supporters; some of them went so far as to offer me to double the price of subscription to enable me to go ou, which, however, I did not do, being alone.

Should you think proper to answer this letter, and to make any remarks upon its contents, I ehould bo very glad to see It In the English Mechanic

Ch. Bauachk, Morchain, Somme, France.

[M. Rabaohe complains of the want of freedom of discussion in France, and attributes to the Editors of French scientific journals the most mercenary motives. We believe the charge Is untrue. If M. Kuba che cannot got his communications Inserted let him seek for the solution of his non-success in himself. With the above letter ho has sent us other contributions which would fill seven or eight of our columns, which we would not insert even if he paid us, unless the said contributions appeared amongst our advertisements. Our opinion is that M. Rabache's wordy, rambling, conjectural communications nre not worth inserting, and iu all probability Editors of French scientific papers are of the gamo opinion. In fact, M. Itabachels a scientific bore, ordinarily, we should be more tender towards a foreigner, but as this one has not scrupled, as wo think, to malien the motives of honourable men—some of whom we know to be zealous searchers after truth—it ie requisite that things should be called by their right names. M. Kabache has mistaken bis mission. We respectfully submit to his attentive consideration the papers on "Science for the Young," now appearing iu our columns. Let him cultivate the spirit of a learner before he assumes the attitude of a teacher.—Ed. E. M.J

PLATINISED GAUZE BATTERY.

Sir,—The platinized gauze battery, recommended by " Sigma,** can be made with two pieces of gauze and a plate of thick amalgamated zinc, about the same size. Two thin strip* of wood, or ebonite, should be put between the gauze and zinc, secured by a Smee's clamp. In making this form of battery, the sauze should be "dipped" in aqua fortis, not dilute nitric acid, and electrorypod by the Ringle cell process, or by a DanielTs battery, it is then to bo well plated with about loz. of silver to the square foot and platinised. Daniell's battery is the most suitable form that cau be used for electro«plating on a small scale, but I have found nothing better than platinised carbon for gliding. J. Round.

THE TELESCOPK.— MR. BUCKINGHAM'S GIGANTIC REFRACTOR.

Sir.—Your able correspondent, "F.R.A.S.," p. JÍS, says, concerning this instrument, that "regarding its optical performance, we have as yet no definite, report" published. Allow me to remind him, that at the meeting of the Mociety, January 14, 1870, and published, Mr. Buckingham said, he had been observing Jupiter before coming Lo the ineotiug, with the telescope referred to. which was ;¿ll¡n. aperture, aud he found th"? reddish equatorial belt resolved Itself into markings,apparently like marbles, with a whitish busis between them, suggesting the idea of clouds, and :i photosphere vUiMe below them. He had also noticed a new bolt since yesterday, and mentioned some observations with the spectroscope. T. V. B.

of great good. It Isla no fault-finding mood that I beg to draw your attention to one or two slight errors which occur in a letter, pp. 157 and 156. First, the Howe and Thomas shuttles are exactly the same In size as regards thickness. I measured а В Howe and a No. 2 7-10 Thomas, those being the corresponding machines. Thus, in this particular their virtues arc equal. Then, as regards the quantity of thread the different shuttles hold, I find Singer holds most. Thomas next, and Howe the least, the Thomas shuttle reel being fin. longer between brass ends, and also larger in diameter than Howe's. I quite agree with ell that is said respecting the Sluger shuttle, or crank action, ie being far from correct. At tbe same time, the cams of the machines he mentions, in my opinion are far from being up to the mark. Let me begiu with the Thomas cam. This moves tho shuttle to its furthest extremity beforo tbe needle moves upwards; hence the needle thread is pulled up between end of siiHttle carrier and shuttle, when the shuttle thread is at its tightest. This must Injure tbe upper thread to a certain extent, and forces tho operator to keep a loose tension in shuttle. Again, in the Howe the upper thread is pulled from between driver and shuttle at an angle, which also has the effect of Injuring the upper thread, and causes irregularity iu the stitching if the needle thread ehould be uneven.

Now, I have a machine on Howe's priuclplo mado by Messrs. Jones and Co., in which all this is obviated. The action of the cam forces the shuttle forward directly opposite tho needle, then pauses while the needle In its upward movement, disengages the upper thread from between the .-buttle andcarrior, then, simultaneously with the needle, draws its thread tight. This, In my opinion, is the correct theory, and practice confirms ft, as I find 1 can do tighter and better work on a machine of this description than on any of the others.

I have been a user for 12 years, during which time I have used the Thomas, the Singer, Howe (American), Bradbury (Howe principle), and Jones and Co.'s (Howe principle}, all of which will do good work.

I ehould like to see "Practical Man 'a" opinion respecting tho pause spoken of above. Study.

JUMPING FROM A TRAIN.

Sir,—The view expressed by "O. W. W. G." Is undoubtedly the true one. I had not touched on the way iu which the backward jump ehould bo effected; only of (Ли I was and sm certain,from experiments of my own, that by jumping energetically backwards (really backwards as regards attitude, as well as regards motion of train or carriage) an important aliquot part of the forward motion may be neutralised. In the case of a runaway open ^carriage, I nm certain, from experiments I made some years since from trucks moving at different rates, that a very sharp spring over the back of the carriage, all tho ent-rgy of the body being employed to give motion horizontally from the carriage, would result in a very safe and easy fall, because one can neutralise the forward motion almost wholly. I am sure that In some Instances where I trieb, the experiment, the velocity of tho truck must bave been very nearly equal to that of a runaway carriage; but the truck had no back, so that it was easy to glvo an energetic spring.

R. A. Proctor

DARK LINES IN SOLAR SPECTRUÄL

StB,—Your commente on "T. A.*e" letter leave noihiug to be said by me on tbe point you deal with. As regards " T. A.'s " doubts, I could have resolved

them af once, had he, in his firet letter, simply asked on whnt evidence physicists grounded their belief that the dark lines in the solar spectrum are uot due to our

SEWING MACHINES. Sin.—I hail with delight the articles now appearing upo:i the sewing machine, considering as 1 dit that tho information contained therein will be productive

own atmosphere.

Long before KlrchhofT *s great discovery (admirably j described by *'F.R.A.S.** in tho last number of tho ч Mechanic), Brewster had noticed that certuiu dark liues make their appearance when the sun is low. J These are doubtless atmospheric. On the other band, si there are certain lines and nebulous bands (doubtless" , resolvable into lines) which are only seen, at least with ordinary spectroscopic power, when the sun is high, ,' These are doubtless true solar lines, so faint as to be very readily obliterated. The remaining linescouttuue visible whether tbe sun is high or low. Nor Ио they ^row narrow, as "T. A." supposes they should when the suu sinks low. It is contrary to the very essence and principles of spectroscopic science that they should do so, oí, conversely, that the atmospheric lines should, grow wider as the sun sinks low. What really bappens is, that the lattor lines grow darker, because as the sun sinks ho shines through a greater and greater, depth of our atmosphere, and so tbe atmosphere moral completely absorbs those rays which its vapours bava power to affect. Rays of greater or less refiaugibility (that is, rays falling on either side of any atmospheno. dark lines) our atmosphere canHot affect, let its dtiw sity be increased ever so.

Now, it might seem that-, by parity of reasoning, the solar dark lines should grow fainter as the suu hinksj but on consideration "'l. A." will sco that they willj continuo relatively as strong, whether the suu is higH or low; for our atmosphere neither adds to nor киЬ-| tracts from the quantity of solar vapour throu^H which these rays have passed. The spectrum «rows fainter, however, as the sun sinks, a»d so tbe sola! lines do undoubtedly, pro tantoy diminish in diej tfucmess.

1 cannot close this letter without gently rem Indino "'IV A.*' that our physicists are too earnestly imganed In seeking after truth to overlook such very otniouJ considerations as nre sometimes urged against Uniij theuries. Let me quote on« passage, iu which Kirch* hoff présents a portion of his results, iu order th и Им spirit of the true man of science may bo xeoogoised of ■*T. A." and other»:—

"The observad phenomenon, may bo explained hi the supposition that the rays of light which form tt solar spectrum have passed through the vapour < iron, and have thus suffered the absorption which tb\i vapour of iron must exert. As this Is tho ouly a*:>iga able eause of this coincidence, tho supposition appeal tubs a necessary one. These iron vapours m ¿¡ht b

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contained either In the atmosphere of the nun or In that of the earth. But it 1« not onsv to understand how our atmosphere can contain auch a quautitr of Iroq vapour aa would prn.'uee the very dn-tinct'iibsorption lince, which we (tee in the solar spectrum. And this supposition is rendered still less probable by the fact that these lines do not appreciably alter when the sun approaches the horizon. It does not, on the other hand, веет at all unlikely, owing to the high tempers turewhlch we must suppose the sun's atmosphere to possess, that such vapoure should be present in it Hence my observations of the solar spectrum appear to me to prove the presence of iron vapour in the solar atmosphere with a* great a degree of certainty as we can attain la any question of natural science."

This patient labourer in the Heldof arduous research, this cautious and clear-sighted reasoner, this modest and unpretending philosopher, is one of the''tricky knaves," the "shifty, dodgy liars" of Mr. Hampden; is " one oi the class of men who, next to horse-deab-rs and jockeys, bear the unenviable reputation of being the most tricky and unscrupulous in their assertions." And of Mr. Hampden let me say this, in passing:-I think nothing he might write, or say, or do, could bv any possibility cause scientific men even a passing annoyance; but I do hope that he will never so far try their patience aa to endeavour to fix on them the stigma and deep disgrace of his approval.

11. Л. Proctok.

COILS.

Slit,—Seeing D. Forbes'я description of his coll (Я715 p. lfiO), I think it a wise decision on hi» part to let his coil alone, for it is a verydlsproportlonate-slzed one, and I doubt if ho could lengthen the spark either by winding over again, or adding more wire. The size core generally used for a coll 12in. long is about lin. diameter (8 times the size of his wire. The variety known aa "soft charcoal," is the best for cores. He seems to have rather a queer notion with respect to the secondary. He aays"bemade his ooil . . .withadisc in the centre dividing the secondary in two, joined by я fiter of сорр'т at tho bottom of the centre disc going through the dite." The ususl way to divide the secondary la to wind a layer the whole length of tho reel, insulate it all along with about о layers of tissue, thon slip the disc over it and fix it there with parnflin wax, and wind away back to lin. or Jin. of the disc. This is rather different to joining tho sec. by a "piece of copper," which, I presume, means a slip of copper. 1 make it a practise to seal up the edges of the tissue which are left against the sides of the ends and disc with paraffin. The spark, which might otherwise travel along the tissue down to the next layer by the absence of Insulation (being prevented by the thickness from going through it) would (bv sealing the tissue up against the sides) be prevented from passing. 1 should recommend him to use a glass or vulcanite tube ¿in. thick to enclose the core, and wind the primary directly on to it, covering the wire when wound well with insulation, and then wind the sec. on this, dispensing with lignum vitas reels altogether. He ought to put 81b. Instead of -lib. or sec. on a coil I21n. long, and get a Tin. spark from it. He could notnse ft better wire than No. ЗЯ; if he used thinner the spark would certainly be longer, but it would be thin and wiry—of no use In some experiments. The best wire for primary would be No 12 cotton. Two layers of this would be sufficient, taking nearlv 51b. for the two. If he used a thinner wire, he would have to use more layers to magnetise the core to the same extent with a given battery power.

In addition to G. P. tissue, I And paper soaked in melted paraffin an excellent Insulating material. Unsized newspaper Is the most preferable for this.

I hop? tlies ■ will be the suggestions he asks for ; being based on experience, I am виге of their correctness.

A. E. Tucker.

THE EAETH'S FIGURE AND ROTATION.

Sir,—Now that Л1г. Beardsley has so kindly come forward to putus right upon the above subjects, i think we nmst not let him go without getting ад explanation of all the appearances, celestial and otherwise, which are commonly said to result from the facts that the earth does rotate, and is of a round shape. For example, the shadow thrown on the moon in an eclipse, the fact of circumnavigation having been effected, coupled with the circumstance that ships are a day out in their reckoning of the time, one way or another, according to the direction in which the voyage is periormed. and several other little circumstances which we must not fail to put him tu mind of. It is rather too bod to expect such men as Mr. Proctor to waste time and trouble about snch matters; it is like getting a professor of six or seven languages to argue with a precocious jnvenile who Insists that the alphabet is all wrong because the letter О is made round instead of square. I admire Mr. Beardslev's diagram of the sun's apparent diumal motion, but can't make out how he brings the sun back so aa to start all right in the morning. But this Is an "error of vision " on my

fart, no doubt. You see I do not argue on the subjects mention above, because they are in every book on Natural Philosophy, and do not therefore require repetition. I will undertake to und .Mr. Beardsley in things to explain —and some uncomfortable things, too— which he w 111 find not so easy as he thinks, Judging by the style of his letters. To my eye the roundness of a dew-drop Is quite sufficient proof of the shape of the earth, considering who was the Architect of both. Mr. Beardsley says he does not hold that the earth is a vast plane. If nota plane, and not a sphere, what shape is she? Sack-bag shape, perhaps, which is neither round, square, nor oval, as I once heard. He ought at least to let us know what shape she really Is, as otherwise some nervous individuals may fear to go out after dark, as they will fancy every bank to be an edge over which they muy tumtle Into space.

H. G , Salop.

TBE MOA OR DINORNIS.

Sip,—T а-n glad to »ее " Urban " has returned to the ranks of "sur" correspondents, and note his re

minder of an old discussion, as to his last remarks on which some timo since I Intended to have said something. He refers to a letter in Katurr arguing the probability that the Moa existed during comparatively very recent periods, and was known to the present aboriginal races. It is, of course. Impossible to come to any certainty on such a subject. and I do not pretend to any actual knowledge The discussion, If it can be called such, arose from a joke of mine as to the cause of cannibalism being the want of aulmal food ; "Urban " suggested that the canuibnl NewZealanders had the Moa in abundance. The letter now referred to was called forth by a report of a Hermanmeanwho has been exploring New Zealand, and come to the conclusion that the Moa had boon extinct inaay hundreds of years, which is my view of the matter, and, further, ho says that he had examined the remains of ancient encampments, nnolagous to those our savage ancestors have left in old caves, and found many bones of tho Moa, but mostly of tho small species, and with them those of dogs, gulls, and whales, but found no suman bones, indicating the probability that the race which had these sources of food icere not cannibah.

I was much interested by "Urban 's " lastlettcron the subject referring to Arabic records, but I musr say that, in my present state of information as to these, I feel a strong convleiion these are misunderstood. My acquaintance with Arab senmen. and especially Arab vessels, even of the preseut dav, does not Induce me to think It likely that they had explored the southern seas In the 13th century.

These early Arab navigators were but wandering merchants seeking markets, or else pirates looking for goods and people to steal as they do to thlsday ; but they weremlBcrablyequlpped, provided only for short coasting trips, and without incentive to urge, or knowledge to give them courage to truverse unknown seas out of sight of land: and. further, they were unmitigated liars, a« also they remain, and their tales have little more value than those of the celebrated voyagtur Sindbad, whose " roc," by-the-byc, was uo doubt based upon some accounts of these very birds, and others of similar magnitude, natives not of New Zealand, however, but of Madagascar.

At the same time it is Just possible that creeping about among the eastern islands, some stragglers might have iound their nay through Torres Straits or round New Guinea, and then blundering on the north of Australia, been blown out to se.i and struck New Zealand, The difficulty would be, in such a ense (and bysuch means these islands were probably peopled), how they got back again, with the then existing knowledge of navigation, япЛ unaided by the compass, unless they picked that up from some far travelling Chinese junk, as that now stagnant race of early Inventors claim to have known this instrument from very early times.

However, if the Arabs spoke frnlv, all they prove is that the Moa existed while New Zealand was uninhabtted. That by no means prevents the conclusion that they were soon killed oil by the early settlers, most likely shipwrecked and starving, and that cannabalism arose after the supply wasexhausted.

Sigma..

TURNER'S ENGINE LUBRICATOR.

Sir,—I intended writing lost week about the description given by Messrs. Turner of their lubricator; however, 1 find another correspondent (" B. Wit ") has In tbis week's number noticed It. I, like "It. W. R.," would like to know in what psrt consist» the patent, because some few years ago a lubricator of tho very same principle was made near Manchealcr, and I am informed that the maker ceased making them. I went, about two years ago, to Rochda'e, to see one of the«e lubricators at work, but I did not like the principle of It. as itappearcd very clumsy, and too much complicated: and furthermore, I thought there would be great difficulty in preventing the tallow passing the piston or plunger of the lubricator from the underside of plunger to the topside. Again, there was also a disadvantage In having to reverse tho piston or plunger by hand labour to refill. However, I was at that time looking out for the best self-aoting lubricator that would lubricate the valves and pistons efficiently (working 701b. pressure per square inch), and a few months afterwards I was informed that a Mr. Butterworth, of Oldham, had taken out a patent for a lubricator that would suit me. Of courss, 1 first saw the principle, and approved of It It is now about eighteen months since we lmd the tiret one applied; we have now four of them working. I can assure my brother engineers that they have been a great assistance to me; they require no attention, only keeping clean.

For the information of my brother engineers, I can only say that I have not as yet seen nny to surpass them, as they supply the valves and pistons constantly with the lubricant wheu the engines are at work, and the supply can be regulated at will. They work so eaey. that they require not to be screwed down. The tallow can be put in the box while working; it starts and stops with the engine.

I have been looking over rav back numbers, and I And it was illustrated in our English Mechanic of January 29, ISO». Engineer.

EXTRACTS FROM CORRESPONDENCE.

COMMERCE AND TRADE,—" Herbert" save :— "In answer to the query of ' faul Rymea.' who quotes the sum of the imports into the United Kingdom for 1808 as £294,693,008. and tho exports as £179,077,812, I say that those figures indicate a very lucrative trade. If 1 freight a ship with a cargo which costs me £18,000, and she brings me back n cargo in lieu oi it, of the value ot £S9,000,1 think mv trade would be very 'prosperous.' Now, If I individually should prosper doing a trade giving such returns, so does the nation of which I form an unit."

STAINING OAK.—" Faber " writes :—«' Some time ago one of your correspondents asked the above ques

tion. I was anxiouB to seea reply, but looked In vain. I have since tried several experiments with acids, and dud the best stain to be equal parts of American potash and pearl ash—2d. worth of eaeh to about n quart of water. This will give a strong stain, it requires careful application, as the American potash is a strontr solvent and will blister the hands ; ft softens a good paint brush once using, so 1 get a very common brash, and apply the stalningwith it. I keep it corked up In a bottle, and it is always ready for use ; if It strike* too deep a colour add more water."

THE"HARMONIOUSBLACKSMITH."-"ji Rugby " wrt'es :—•' Thanks to our harmonious for his extract from 'non-historic times 'oil's architectural remains in India.' but why didie not give us the source from whence lie drew bfa ideas > unless the "H. K." is In reality either Sir John Lub'. bock or the ■ Quarterly Reviewer' in disguise"

[rosslbly the " H. 1!." is the latter.]

THE PEDESPEDE.-S. F. Shakespeare, of Thrapstone. says .—" I see your remarks In the Mechanic »f May 0th, inst,, about the pedespede invention. I regret you seem doubtful, and appear to think it must be hujtful to any one using them. I, however, beg to assnre you this is not the case. By the appliances I make use of in those I constructed, no danger would arise, whilst every comfort is allowed for the person using them, as he Is able to use Iiib feet and ankles easily, the same as during skating on the ice."

ALGEBRA. — «T. J. O'C." observes : — " Sine« almost every arithmetical solution which appears In the pages of our valuable journal is solved by means ot algebra, and knowing that there ¡are severa brother readers complete masters of this beautifnl science. I hope that some of them will lend his heiping-hand during his leisure moments, and confer on his brother readers a short discourse on this valuable science."

THE "PHANTOM" VELOCE.—The following are extracte from letterejust received:—"1 wish Mr. E. M. T. Tydeman lived in my neighbourhood (Marlborough), to mount my 'Phantom' just once. He would then be convinced that he has made a great mlstakein speaking against the 'Phantom' with rubber tires, as certainly there is no comparison with ordinary wheels. The nearest I can compare Is ridlno- tu a broad-wheeled waggon full trot an«! the riding Гп я cairiage."—G. JoNEB.—Mr. St JohnT. Gore,of Eaton Place, Guernsey, says:—'■ Having noticed a letter from Mr. G. Sykes, of Huddersfleld. relative to the 'Phantom? wheel, as made by the ■ l'haut.im ' Wheel Company, I think it only fair (especially sfter a letter from a Mr. Tydeman that appeared in your paper some little time since) to state that having tried a pair of the above wheels, with india-rubber tire», in my bicycle, for the last three weeks, I ean fully endorse Mr. Sykes' statements concerning them in every particular, with tho exception; perhaps of the weight, although they are undoubtedly lighter than many bicycle wheels."—G. S. Cole, 8ea Side, Llanellv. says:— "Having the front wheel of my bicycle broken, I scot for ouo of me rnbbcr-tlered ■ i'hautom' wheels, with axle, cranks and pedals complete; and I am of the nmc opinion as Mr. Sturge«. or Ни idcrsfield, respecting it ; and I may add that several from ths town and neigbourhood have sent.and sreabont sending for the same. "С. H. Maxsted, of Ca-t'e Park, Lancaster," says:-" I have tried the • I honicm' veloce wheel, and Und it much superior to tho ordinary wheel, and fully endorse Mr. SyktVs sentiments."

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REPLIES TO QUERIES.

[2007.]-TEMPERING DRILLS.— Овсе тоге Г "Tie a pity " S- T." Bhoald pase unanswered, since iie took so much paine to get off the printer'« shoulders, where he was но considerately placed by "J. B." Steel is hardened by being heated to redness and then quenched suddenly In some cold fluid. Tempering re not hardening-, at " S. T." affirms in the sentence led off by that word, page 139, but я meana of reducing the brittlenees of hardened steel, which unhappily cannot be performed without reducing also the degree of hardness. Annealing either hardened or soft ateel consists in heatfng to redness nnH allowing It slowly to cool; the effect of which in the case of soft steel is rather doubtful, unless performed in charcoal dust. If "S. T." can either harden or temper by the procesa bearing his signature, which we have in good set terms and black and white at раке ID—namely, " Heat your drill to a dull red, allow ft slowly to cool," Ac, we can also gire him credit for b?ing able to shot his eyes by holding hie breath. At any rate, if he will not see now that he Is, to say the least, confounding two different things, he Is shutting his eyes with a vengeance somehow or other. The whole of hia "reply to the criticisms of * J. В.' м ts nothing in the world but making a rope of sand. It Is curious to notice how correspondents, when set right, nhow at once if they feel themselves equivocally placed, by assuming the cfrcumlocutlre style—Nobody.

[-374.]—BREWING.— "New Subscriber "beg« to thank "A Reader of Old Books" and " W. L." for their Information. He has just received a very elaborate work, but shall bear " W. L." in mind.

[2402.]—ELECTRIC BELLS AND BATTK RÍES.— If A. Spencer winds his coils with about 'ioz. of No. 28 silk-covered wire, and uses 2 cells of manganese, or 3 cells of sulphate of lead battery, asdescrbed by mo in the same number of our Mechanic as that In which bis query appears he will find his bell will ri a g furiously.—A Good Boy.

[2522.]—SHEET IKON RUDDER.—Some people are not content with baring a canoe with as few appurtenances at possible, but invariably endeavour to convert It into a floating lumber shop, carryfug twomasts instead of one, which is quite sufficient if there Ь any thing fit to be called a sail for It; я Jib which is na use, a boat-hook, ovshovlng pole, creep, cable, cook

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