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from the Admiralty, exulted over the failure of the ship lungs, but his triumph was short-lived, for, in the course of a few years, he found that he was left out in the cold also, and the old wind-sails were again on duty.

The illustrious names of Count Rumford and Sir H. Davy, as well as those of a host of other persons less celebrated, which figure in the annals of ventilation, attest the importance of the question. It is time, however, for me to take leave of this portion of my subject, on which volumes might be written, and to consider the causes which make ventilation a necessity.

These may be classed under different heads, viz.: 1st, In private houses. The necessity for ventilation will arise from commonly (A) the presence of fires ; (B) artificial light; (C) the presence of persons living in the house, that is from the air required by them, as well as the exhalations from their bodies, and (D) from badly constructed water-closets, cesspools and drains. 2d. In factories there will be, in addition to the above causes, the presence in the air

of a vast quantity of minutely-divided fibre and dust, which is highly prejudicial to the health of the workers, and also the fumes from chemicals, etc., where the manufacture of such is carried on. 3d. In sewers. The necessity of sufficient ventilation will almost entirely arise from the generation of poisonous gases by the putrid filth carried down. 4th. And in underground railways, the fires of the engines, and the saturation of air by the waste steam, will render ventilation, in certain cases, necessary.

Considering these cases in the above order, we have 1st, in dwelling houses (A), the presence of fires.

At first sight it would seem an error to include this under the head of causes which make ventilation necessary. As fires are often, indeed mostly, the only means of ventilation in private houses. But under the term I include not only the removal of foul air, but the supply of fresh, and from this point of view it will be seen that the common fire is a very great consumer of fresh air, and requires a supply of that

quite as much as of the fuel which feeds it.

It may be as well to mention here some of the well-known facts connected with the combustion of fuel.

The fuels commonly used are composed, principally, of carbon and hydrogen in about the following proportions :

Name.

Carbon Hydrogen. Ashes, &c. Water.

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Now, combustion consists in the union of oxygen gas with the elements carbon and hydrogen, and the result is a development of light and heat, and the formation of carbonic acid and water, the carbon of the fuel uniting with the oxygen of the air to form carbonic acid, and the hydrogen doing the same to form water.

Carbon exists in its pure and crystallized form as the diamond, and this beautiful gem is combustible in oxygen gas, burning entirely to carbonic acid. This experiment

has been tried, however, only in the laboratory.

One pound of carbon requires for its combustion 158 cubic ft. of air, while the same weight of hydrogen requires 473 cubic feet. From these facts it will be seen that the different fuels mentioned above will take for their proper combustion the following minimum quantities of air, viz. :Coal......

148 cubic feet) Wood.

65 " per pound. 147

134

Coke..

............ Charcoal........ Peat.......

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There is a certain quantity of oxygen in coal, wood, and peat, which somewhat reduces the amount of atmospheric air required by these fuels.

From the above tables—for which I am indebted to the researches of Péclet, Playfair, Regnault, and others, and which assume the temperature of the air to be 26 deg. F.—it will be seen that the ordinary fire plays no unimportant part in the consumption of air; for, if we assume one pound of coal per hour as the quantity required, then 148 cubic ft. of air will be con

sumed in that period, or 2.46 ft. per minute, or 2,072 cubic ft. per day of 14 hours.

These, as I have said, are minimum quantities. In practice, at least double must be allowed, as a large percentage will escape unconsumed.

In the case of the common fire, the products of combustion do not certainly escape into the room, but the air to supply the fire is required all the same, and I feel sure that not in one house in a hundred is this supply ever thought of, but is left to chance, and the cracks in the doors and windows from which drafts whistle across the room in every direction.

The second cause (B)-artificial lightrequires far more serious consideration than the fire, for, commonly, the products of combustion are passed directly into the room, and are breathed in a diluted form by the persons in it.

The introduction of coal gas has been most pernicious in this respect, for few houses are built with any regard to the method of lighting, nor are the ways in

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