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104 REPORT OF EXPERIMENTS ON THE EXPLOSIONS OF STEAM-BOILERS.

and removed. Care was taken to ascertain that the stationary point, given in the cylinder, was the same with that shown by the naked thermometer. As some of the alloys expanded considerably on congealing, it was supposed that the cylinder might prevent error from the compression of the bulb of the thermometer, but no such compression in the instrument used was detected by frequent trials.

As the alloys were intended for ordinary use, it was deemed advisable to ascertain how far the impurities of the metals, as they

occur in commerce, would cause a variation in the fusing point. Tin has a very uniform purity in commerce, the grain or stream tin being always accessible. The bismuth of commerce being obtained principally from the native bismuth, is probably not very variable. The lead contains variable quantities of silver, copper, and iron. The first experiments were made on the fusing point, on various specimens of common tin: this tin showed, by re-agents, a trace of iron and of copper, as impurities. The fusing point of grain tin is 442° Fah.

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It is proper to state, however, that some specimens were procured, obviously obtained from the sulphuret, and contaminated with it. They were not used.

REPORT OF EXPERIMENTS ON THE EXPLOSIONS OF STEAM-BOILERS.

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105

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Mean,

An attempt was next made to ascertain what effect the impurities shown by the fusing point of lead would have upon the fusing points of alloys, into which it entered. Alloys, in atomic proportions, were selected, as much was expected from them in the way of avoiding the slow passage from the liquid to the solid state, which was observed to be the property of certain mixtures of the metals. Alloys of tin and lead were therefore made in atomic proportions; first, of grain tin and the lead already spoken of, from the Paris mint; the second, of block tin and common lead. The tin was employed in multiple proportions, as being the more fusible metal, it would probably enter more largely than the other, into the composition of fusible plates for steam-boilers. The equivalent of lead is 104; of tin, 58; the first alloy was composed of the two metals, united in this proportion, the total weight of the components being about ten ounces, troy; a new equivalent of tin was next added, and

Equivalents of

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o on, through the series: the results are given in the following table.

Upon this table we remark, first, that at all the stationary points, except in the alloy of 1 lead to 2 tin, the metal was solid at the stationary point; second, that although the proportion of tin varied from one to six, and even to seven, the stationary point was not changed more than 34° for the first series, and 51° for the second; third, that in the proportion of one of lead to four of tin, a second stationary point appeared at the point at which the metal began to lose its entire fluidity, and was found in the higher parts of the series, rising with the increased proportion of the more fusible metal, with difficulty detected at times, and disappearing by agitation of the alloy; fourth, that the tin and lead of commerce give, for the lower stationary points in the same alloys, quanti ties nearly the same. A comparison of the upper stationary points appears on next page.

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Number of Observa

tions of which the

stationary point is the mean.

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REMARKS.

2

1

Begins to lose fluidity at 430°, soft solid at 410o, do. 400°, still yields to a stick at 3504o, rises to 354%, the stationary point, hard and unyielding.

Thermometer fell to 35610, metal still liquid, congeals very irregularly, rises to stationary point, parts of the metal still fluid.

Thermometer fell to 365o, rose rapidly to 369o, where it was stationary for a short time, then fell to 357, where it was stationary for some minutes.

Thermometer was 30 secs. in falling from 3694° to 362, very slow: stationary at 3573 for 100 secs. No other stationary point to 200o.

Thermometer stationary at 377°, in one experiment, then fell to 358°, stationary 35 secs.: at 377 soft solid, easily penetrated, hard at lower stationary point. In another expt. fell to 377°, then rose to 3790, whence it fell rapidly to 35830, the lower stationary point.

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REMARKS.

At 40840, a stick only pierces the surface, solid below. Thermometer fell to 352o.

Parts of the alloy liquid at stationary point.

In one experiment thermometer rose from 36640 to 367°, alloy granular, semi-solid; fell to stationary point, alloy solid. By stirring, the upper point was obliterated.

In one experiment the thermometer rose half a degree from 37630, then fell rapidly to stationary point.

Thermometer rose half a degree above 38340, in one experiment, and was stationary a short time at 38110. in another experiment; at both these times the metal was beginning to lose fluidity. Solid at lower stationary point.

Thermometer fell very slowly from 387° to 3861, and alloy began to congeal at surface.

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of

Lead.

Tin.

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378

The variable nature of the results, seems to point out rather the difficulty of detecting the upper point and the effect of accidental circumstances, than that it is affected materially by the impurity of the metals as found in commerce. This upper point rises with the proportion of the less fusible metal. The number of degrees between it and the corresponding point, for the solid state of the metal shows one difficulty to be obviated in the use of the fusible alloys. For example, the first in the table, just given, has 103° between the point at which it begins to lose fluidity, and that at which it is solid; the second has 11°, and the third 293°; these defects, it was hoped, would not have been

376
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found in alleys in definite proportions. They indicate that the variety of combinations in definite proportions is not considerable, if even it exceeds a single one; and that when the metals are mixed in definite proportions, the alloys are in fact combinations, or mixtures, of one or more chemical compounds with the metals themselves. If this be the case with alloys in which the proportions are in the ratio of the equivalents or in multiple ratios, it would seem to follow certainly, that in alloys made in proportions not definite, the same fact would appear. That this is so, and that its effects are of importance in practice, will appear subsequently.

(To be continued.)

EQUATIONS FOR RAILWAY INCLINED PLANES.

Sir,-The concluding remark I made in my last article (No. 661) was, "If a few experiments of this kind were made upon planes of different inclinations with full loads, &c." Upon second thoughts, I find that the experiments might all be made upon a level plane with variable loads in the following manner:

Let Lweight of the engine, train,

and load, and suppose the maximum velocity on a level is Ve miles per hour, then by augmenting L by its mth part it

L becomes L +

L

m

; then with the weight

L+ let the maximum velocity on a

m

EQUATIONS FOR RAILWAY INCLINED PLANES.

level be experimentally determined and found to be V1 miles per hour; th n

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107

The average variable velocity will be 1⁄2 (V° + V16) = } (30 +24) — 27 miles

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sponding to the weight L moved up a plane rising 1, 2, 3, 4, &c. feet per mile. In all the cases it is supposed that the steam is so regulated as to produce a maximum effect.

Suppose the full speed on a horizontal plane with a moving weight L is 30 miles per hour, and that with this speed the engine and train began to ascend a plane rising 16 feet per mile, and that it has been experimentally found on a level that the velocity due to a rise of 16 feet per L

mile, or to a weight (L+i) is V16 =

24 miles per hour; it is required to determine the time of ascending the plane, the average variable velocity, the point in the plane where the velocity becomes permanent, supposing the length of the plane to be 6 miles?-See Mech. Mag. No. 661, p. 14.

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Sir,-At the head of the "Notes and Notices" in your last Number (666) there is an extract from an article in Silliman's Journal on currents in water, where it is asserted, "that if a tub or other vessel is filled with water, and a hole made near the middle of the bottom of it to discharge it, the water will acquire a rotatory motion from west to south, or opposed to the apparent motion of the sun." The Guernsey Star remarks," This cannot be the effect of chance, but of natural laws constantly operating." In the same Number of your Magazine there is a communication from a correspondent, W. B. of Nottingham, wherein he states, that he has observed, "that the common scarlet runner, or French bean, always twists in one direction round the stick that supports it;" but he has not observed, or at least has omitted to state, that the direction which the scarlet runner takes is from west to south, or that opposed to the apparent motion of the sun. Again, the real motions of the planets is in the direction opposed to the apparent motion of the sun. Whether the same law governs all these motions, and very probably many more which have hitherto escaped our notice, is what I do not pretend to determine. Whether the same natural power that moves an atom moves a world, or whether, agreeable to the "Mackintoshian philosophy," electricity is the great moving principle that keeps all in life and motion, I am not philosopher enough to give an opinion; but I was

108

RAILWAY-CARRIAGE BREAK.

struck with the coincidence upon reading the above extract, and thought it worth recording. There may possibly be some great law of nature peeping forth through this small aperture, and which, if the opening could be dilated by a few additional facts, might instantly emerge into broad day.

Yours, &c.

TREVOR.

MR. JOPLING'S RAILWAY HINTS-RAIL

WAY-CARRIAGE BREAK.

Sir, With due deference to Mr. Jopling, I beg to state, that the idea of applying bands or straps to locomotivecarriages, however new or novel, on railways, is not so as regards steamcarriages on common roads, a patent having been taken out by an eminent engineer some few years ago for the purpose; I believe, however, it was never brought into practice. The smooth and equable motion of the carriages on railways is certainly a powerful argument in favour of its adoption; as is also the introduction of the method used by Mr. Russell in his road steam-carriages; namely, dispensing with the crank-axle, and substituting either cog-wheels or wheel and pinion, thus gaining either power or speed; also taking the action of the engine off the propelling-wheels in an instant. A sort of basket, to precede a train of carriages to turn any impediment off the railway, was proposed in the Mech. Mag. No. 404, by Sir G. Cayley some years ago.

Since the opening of the Greenwich Railway, I beg to state, that I have contemplated an addition to the locomotivecarriage, in the shape of a break,* applied either to the propelling-wheels, or to the whole four. The method is easy of adoption, and the mere act of shutting off the steam will bring the apparatus into play. As I cannot, however, just now spare time to make the illustrative drawings, or complete an experimental model, I must, for the present, withhold further communication on the subject, and am, Sir, your obedient servant,

J. ELLIOTT, Machinist.

14, Stacey-street, Soho.

• We have been favoured with a description of the break now in use on this railway by the inventer, and shall give it in our next or succeeding Number. It is a very excellent one.-ED. M. M.

THE LONG-WORK SYSTEM OF MINING.

Sir, I am greatly obliged to you for the information you gave me in your excellent Magazine (vol. xxiv. p. 505), with regard to the mining of coal by the long-work system. You inform us that the Committee came to the conclusion that the present mode of working in the North was better than long-work, and yet Mr. Buddle does not deny that longwork is the best mode of ventilating a mine; and Mr. Mitcheson says, the current of air passing through long-work would keep it clear, and so prove an advantage.

Now, sir, what did the Committee meet and hear evidence for was it not to get at the best mode of ventilating the coal-mines in the North of England, and, consequently, the saving of human life? Did not the evidence prove to them that long-work was the safest way to work the coal, and to subdue the gas, in the North of England collieries? 'Oh, but then we have tried this and the other method, and we like our own best; it is what we have been used to from our youth. And as to the loss of lives, we have been accustomed to that also, therefore we may as well go on as we are.' So, instead of adopting a method that would convey the atmospheric air round the face of the whole working, and to every living soul in the mine, the colliers are still to be employed in holes and corners where no atmospheric air can approach-destruction, ready upon every change of wind or density of atmosphere, to be forced out into the open roads and workings. From that moment the mis called safety-lamp becomes a man-trap.

Mr. Buddle in his evidence says, that he had tried the principle of long-work, generally called the Lancashire system (it is the Shropshire system of long-work I am contending for); but that induced a double mischief-too much small coal by the weight of the top behind pressing upon the face of the coal-If Mr. Buddle's long-work had been long enough and wide enough to have brought down the roof of the mine behind him, it would have lightened the pressure on the face of the coal, and instead of breaking the coal small, would have assisted in working it. "But the chief mischief," he says, "attending it, was the breaking of the strata up to the yard coal-seam,

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