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velocity of 50 or 60 miles an hour. Little as this may have been regarded, it is a matter for graver consideration than it at first sight appears. Passengers are by far the most lucrative for railways. They will not be jostled and knocked about any how: nor will they be alarmed and inconvenienced with impunity. They are a sort of goods that must be kindly and tenderly treated; their prejudices must be attended to and their wishes gratified, or they will not long continue on the profit side of the account.

Whether there would be a saving of expense in the concentration of the inclinations, is a point about which there is some doubt. If a single engine could take the load the whole way, the expense might possibly be even less on a line. moderately undulating than if all the inclinations were united and assistant power required. But if assistant power is to be used at several points distant from each other, there can be do doubt whatever but it would be more economical to bring all the assistant power to work in one place; for there would then be but one auxiliary engine and one set of auxiliary men, and the preparatory expenses of getting the assistant engine ready, would be in the singular number, not in the plural.

It must here be distinctly borne in mind, that in concentrating the planes we must keep the same summit level. If for the sake of having a good line for a number of miles, we ascend to a much higher summit, we shall in all probability pay too dearly for it. Nothing in my opinion but the avoiding of a very bad country would justify such a step.

12. In crossing navigable rivers, roads, &c. it is better to use impetus and sharp rises, than to make swivel bridges or long and expensive embankments.

Engineers, when long tracts of fens and marshes have come in their way, have almost ever avoided them in consequence of the supposed expense of continued embankments to cross the rivers commonly intersecting them. If, however, there is room for getting up a velocity, it is generally practicable to pass them by the force of impetus alone. For if we can get up a velocity of 25 miles an hour, and the engine continues barely to overcome the friction on a level, a perpendicular elevation of less than 21 feet may be overcome by the impetus only; and if the required velocity was 30, 35, and 40 miles an hour, perpendicular ascents respectively less then 30, 41, and 53.5 feet may, by our so often cited table at p. 95, be surmounted. And because it is the perpendicular elevations only that are regarded, the rises

over the bridges may be as brief as we please within reason. Long embankments therefore are by no means essential. It is only needful that the ascents be not so steep as to cause a shock. If this principle was judiciously acted on, there would scarcely be an instance where a swivel bridge would be necessary.

Some have imagined that elevations may be surmounted by alternate levels, and what are termed jumps or sudden rises of a few feet, up which the trains are to ascend by the force of the impetus. I have looked at this view with some attention, and I confess I can see no advantage whatever to be expected. On the contrary, I apprehend a great disadvantage. For the great loss of velocity in ascending the jump-11 miles per hour for 4 feet of perpendicular ascent would occasion such a consumption of time to recover, such a straining of the engine, and consequently would require one of so much more power to get up this deficiency rapidly than would be needed for maintaining a uniform velocity, that I conceive would be seriously prejudicial.-ED.

REPLY TO C.'s REMARKS ON THE HABITUDES OF IRON AND STEEL.

BY WILLIAM MAUGHAM, Esq.

To the Editor of the Railway Magazine. SIR, AGREEABLY to the promise I have so often made, I now sit down to answer the letter of your correspondent C. which was inserted in your sixth number* in reply to a hasty communication of mine which is contained in the preceding number. †

Some of the remarks of C. are ingenious and evidently deduced from experience, but the generality of his remarks are most undoubtedly objectionable, because they are not consonant with the principles of chemistry. Whenever we neglect to make the art of chemistry subservient to the science, we then resemble the benighted traveller pursuing an unknown path with a will-o'the-wisp for his guide. In giving an explanation of the process which I briefly explained of fusing iron and then casting it under water, he

* Page 209. † Page 183.

has, in the boldest manner, advanced theories which, if correct, would shake the present state of chemistry to its very foundation. I shall, in the first place, refer you to what he has advanced in respect to the several states of iron, and to his explanation of the process of puddling, &c., at page 210, and shall next observe that the difference between cast iron, forged iron, and steel, is evidently owing to the absence or presence of two elements, namely, oxygen and carbon; both of which are present in cast iron, but in forged iron they do not exist except in comparatively very trifling proportions; whilst in steel, carbon, but not oxygen, enters into combination with iron. In the operation of puddling, at the elevated temperature to which the metal is exposed, the oxygen in the cast iron combines with the carbon which the iron had acquired in the casting furnace, and they both pass off in the state of carbonic acid gas; but your correspondent C. very ingeniously gets rid of the carbon, by giving it a gaseous form!! Gaseous carbon is hypothetical; it is what C. would call one of the idola tribús; the term, however, has been conveniently introduced in science for explaining the composition of certain compounds of carbon with other bodies by volume, but gaseous carbon does not apply to C.'s

case.

C.'s theory of the cause of the explosions which he conceives would take place during the process of casting iron in the manner I proposed is founded in error. He states that similar explosions take place in the ordinary manner of making castings, and that they are owing to the decomposition of water contained in the sand of which the mould is constructed, by which means there is, as there would be in the case in point, "a formation of a quantity of inflammable gas within the mould-hydrogen, no doubt, mixed with a portion of oxygen."!! For the sake of argument I will admit all this. I will admit that the heated iron may take oxygen from the water, and that the hydrogen of the water will consequently be liberated in the state of gas; but where does C. meet with oxygen gas, or with any other gas, that will form an explosive mixture with hydrogen, for hydrogen gas of itself is not explosive? There is no doubt that, whenever an explosion takes place whilst casting iron in the usual manner, it is owing to the water in the mould being converted into steam by the hot metal; this steam accumulating under pressure, its explosive effects may readily be conceived. If the latter explanation should be deemed unsatisfactory, I would ask, how it occurs that explosions take

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place during the casting of those metals which have not the power of decomposing water, and from what source C. will then obtain a mixture of inflammable gases?

Another objection of C. is, that the "intense hardness of the castings" conducted on my principle, " would in nineteen cases out of twenty be a most important disadvantage; and last, but not least, the plan would be an impossibility except iu a very few cases where iron moulds are used, because the water would dissolve both the loam and sand of which the moulds for iron castings are usually composed." Now, as I proposed the mode of casting iron under water solely for ornamental purposes, as for busts, &c., I did not conceive the hardness which the metal acquires during the process could be at all objectionable, my object being to obtain sharper and cleaner castings than those usually afforded; and as loam and sand moulds must in such cases be entirely laid aside, there would be no fear of the loam and sand dissolving in the water (!) as stated by C.

Let me now call your attention to the following passage in C.'s letter:-"The best experiments of the laboratory must never be depended on; they only afford leading points to which attention should be directed; for the element of heat is so materially altered when practically operating on a large mass to what it is when the experiment is made on a small scale, that similar results are scarcely ever obtained."!!! Every experiment made in the laboratory even on the smallest scale furnishes us with certain data that may be turned to the most useful account in the large way. Matter obeys the same laws both in the atom and in the mass, and nearly all the improvements that have from time to time taken place in arts and manufactures have originated from laboratory experiments. Why does he who operates on tons of matter ask the advice of him who is accustomed to draw conclusions from effects produced from the mutual action of mere particles, and why is such advice afterwards acted upon and found so eminently advantageous ? The reason that precisely similar results are not always obtained on the large scale as when operating after the laboratory fashion is, because in the latter case pure materials are usually employed, which would be too expensive for the manufactory. It is well known that scarcely a single article in a state of purity is brought to market. Heat is nothing more than the result of intense chemical action, it may be modified, it may be augmented, it may be decreased, but it is only altered when it becomes latent, and in that state it

cannot be of service for either manufacturing or laboratory purposes.

C. has by no means settled the question whether iron and carbon combine in definite proportions or not, for his stating "there is the greatest reason to suppose that they do not," and "I think" so and so, is a very per saltum and conclusive mode of arriving at-nothing.

In conclusion I have to observe, in addition to what was advanced in my former letter respecting the casting of iron under water, that the instant the heated metal has filled the mould placed under water at the requisite depth, which depth experience will point out, a stream of water should be instantly turned on in sufficient quantity, by which means the heat will be carried away and thus the water will be prevented from passing to the state of steam, and consequently no explosion can possibly take place.

I am naturally of an indolent disposition, otherwise I might notice many other particulars in C.'s letter, in which he appears to see a mass of things, but few of them distinctly. I remain, &c.

Nov. 23d, 1836.

WM. MAUGHAM,
Lecturer on Chemistry, Adelaide Gallery.

EXPERIMENTS WITH RED HOT IRON AND WATER.

SIR,

To the Editor of the Railway Magazine.

THE following experiment which was related to me a short time since, appears to possess some features analogous to experiments formerly adverted to in your Magazine :—

Two similar pieces of iron, each weighing between three and four ounces, were heated to a bright red heat in a common furnace; two vessels, containing about a couple of pints of water each, were then filled, the one with clean spring water, the other with water in which some soap had been dissolved, both being cold. One of the pieces of red hot iron was then placed in each vessel. The iron put into the clean water almost immediately lost its redness, evolving steam and hydrogen from the water; the other piece, which

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