FIRE-DAMP.

THE great interest which Mr. Samuel Plimsoll has taken in the welfare of sailors has been very naturally extended to colliers, as shown by his article on Explosions in Collieries and their Cure' in the Nineteenth Century of December last; but as he disowns special knowledge of the subject, and states his object in writing to be that of starting on foot a systematic and painstaking investigation of the nature and relations of light carburetted hydrogen,' it would ill become me to criticise his paper except when pointing out errors which, from the circumstances of the case, clash with my argument.

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It is of doubtful accuracy to say that much mischief arises 'because men will not learn, and will not obey, the physical laws of the universe.' Mr. Plimsoll must bear in mind that knowledge is progressive, and that science frequently suspects long before proof can be reached. Indeed, I am inclined to take a different view; for my practical experience tells me men will learn, and do obey, the laws of nature, when there is convincing proof, but they are slow before proof, and, for the sake of stability, rightly so.

The first great step towards the abolition of anything is to discover its source; and as light carburetted hydrogen, or marsh gas, called in the formulas of chemistry CH,, is the cause of explosions in collieries, we should find its origin; but whereas that was not practicable two years ago, it seems so now, and if I have not actually solved the problem, at least I am not far off doing so.

Let me first ask attention to the average of constituents in the construction of plants and coal :—

Here we have before us a visible explanation in figures of the change

that has taken place during the process of carbonising. The proportion of carbon has almost doubled, and seven-eighths (3) of the oxygen, and one-half the nitrogen, have disappeared, leaving the hydrogen free to form hydrocarbon compounds, while the ash remains the

same.

Now what has become of the portion of gases shown in the plants, but which do not appear in the coal? Surely they are still in the coal strata, but in changed combinations, forming varied compounds of which the special object of our inquiry, carburetted hydrogen, is one.

The quantity of carbon which will combine with hydrogen is variable, and dependent on the degree of heat present. At a high temperature hydrogen combines with three times its weight of carbon, forming carburetted hydrogen.

I have now brought down my subject to two problems:

1. During the formation of coal was there sufficient heat to cause a combination between hydrogen and carbon, and, if so, whence is it produced?

2. What circumstances can arise to empower carburetted hydrogen to rush out of the strata with enormous velocity?

Now as to the first. During fermentation great heat is evolved, and that must have been the case in the formation of coal; whether sufficient I am not prepared to say, but there has been another source of heat. Every coal-field has at some period been overlaid by strata which denudation has removed, perhaps 10,000 feet more or less; in which case the heat due to depth would be about 140° Centigrade = 284° Fahrenheit, which would give a pressure of three and a half atmospheres, or, say, of steam 54lbs. on the square inch.

As to the second problem, the matter is of great interest; for the question involved is the vaporising, liquefying, and solidifying of gases.

In order to apply this, it must be understood that the only difference between a gas and a vapour is of degree-a gas being only an attenuated vapour, and a vapour a condensed gas, the visible change resulting from falling temperature or pressure, or a combination of the two.

Carbonic acid gas will condense by the pressure it evolves during generation in a strong closed vessel, and commences to do so when compressed into one thirty-sixth (3) of its volume. If a valve in the vessel be suddenly opened, snow-like flakes will be formed at a temperature of about -80° C., which is solid carbonic acid, or, in more scientific language, solid carbonic dioxide; but the greater quantity resumes the gaseous state. Now the same law applies to all gases; and since oxygen, hydrogen, and nitrogen have been either vaporised

or liquefied, we see our way to the origin of those 'blowers' which are so ruinous when they get the mastery.

Oxygen will liquefy at a temperature of - 65° C.=85° F. of cold, when under pressure of from four to six atmospheres, and also at the moment when it is allowed to suddenly escape into space from a pressure of about 300 atmospheres. Nitrogen requires 200 and hydrogen 280 atmospheres.

It appears that these gases remain gaseous while kept under pressure (for instance, hydrogen has remained gaseous under 8,000 atmospheres); but they liquefy or vaporise on the instant of being set free after the pressures named, and then expand to their normal condition. Under pressure they have parted with their latent heat, and on sudden release the cold attained is intense beyond understanding, even-300° C.

We have similar effects with compressed air, only in a less degree. When sinking a shaft a few years ago in North Wales, I found large volumes of carburetted hydrogen in the strata twenty yards or so before reaching the coal, showing the gas to be of recent origin in comparison with the strata; and I feel convinced that those gases are in the strata under enormous pressure, evolved during the process of carbonisation.

I have known a settling down of strata crumple up 14 feet of solid masonry, as though it were paper, at 600 yards deep, which has its effect also on the gases.

Mr. Plimsoll speaks of a pressure of 30 lbs. on the square inch as if it were a great pressure, and of 1,000 cubic feet as if that were a large volume. What will he say of blowers,' with 500 lbs. on the square inch, giving a velocity of, say, 550 feet per second, and of counting gas by the million cubic feet? Such are the sort of figures we must use when discussing those colliery explosions which occur on a large scale. It is absurd to imagine the possibility of constructing reservoirs in the roof, as Mr. Plimsoll proposes, as receptacles for the vast volumes of gas given off by a powerful blower' that may charge a mile or more of a mine with explosive fire-damp in a few minutes. Allow 400,000 cubic feet to the mile, and the magnitude of his proposed reservoirs will be apparent.

If the difficulty proceeded from a gradual oozing from the strata, the reservoir system might be available; but it is the sudden appearance of vast volumes of gas that is so troublesome, as quantity cannot be foretold.

I have unquestionable evidence that mists from blowers have. been seen and passed unnoticed as 'just a little fog' of no moment; but I am now convinced beyond all doubt that the little fog' was vaporised carburetted hydrogen, expanding to its normal state of gas

ready to combine with eight volumes of air, and fire the mine if a chance light offered.

Having lived in earthquake lands and heard the subterranean explosions before the shake, I believe the bumps and thumps common to fiery seams are only the sounds of the efforts of condensed gases to expand-incipient earthquakes in real fact.

The remedy is tapping the seams by boring to let the compressed gas escape gradually.

J. D. SHAKESPEAR.

THE BREAKING UP OF THE LAND

MONOPOLY.

WHILE it is the habit of certain minds to dwell specially on what they believe to be the fixed and unvarying laws that govern human existence, and to arrive at a knowledge of an absolute criterion from deductions based on these so-called first principles, it is the habit of others to consider the organism and his surroundings as being in a state of perpetual slow change; so that whatever may have been the social laws which have successfully directed our existence in past times, a perpetual modification of these laws is necessary in order to adapt human life at every epoch to its new and altered conditions.

The first mode of mind is the à priori or Conservative one; the second the so-called Radical. Nevertheless we shall see that, rightly considered, this latter form of mental structure is the one which accords most truly with the operation of natural laws, and is therefore neither Radical nor revolutionary, since Nature knows nothing of these rapid changes or cataclysms any way in the history of this world's evolution.

There may be, however, and probably are, points of inflection— critical points in the curve of human sociology, moments when the old is breaking up, and a violent birth of the new is forcing itself into existence. These periods of social crisis may be noticed in the history of every nation. The strain between the various particles of the political body increases until the inherent elasticity of the substance is exceeded. There is a falling apart of the molecules, and a rearrangement of their respective positions with regard to one another becomes a vital necessity. What we have therefore to seek for is that condition of stable equilibrium in the social body where the powers of restitution are complete; and thus, without arriving at that position of rest which is unknown in the physical as well as in the political world, the various members of the social body may ever oscillate about a centre of equilibrium.

There is no question that has so comprehensive an aspect, when judged of by these ideas, as the elementary right of property. The right of every individual to live, and the further right to enjoy the fruits of his own toil, are the axioms from which we can deduce every rational social law. These are the 'natural rights' of an individual Vor. IX.-No. 48.

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