"An Argand gas-burner, in a shop-window, will produce in four hours two and a half pints of water, which may be condensed upon the goods, the window, or any other cold substances.

"The Argand burner of the Boston Gas Company with twenty-two holes will produce in four hours, when burning at the rate of four feet per hour, twenty-two ounces, or a pint and six ounces, of water, and four feet of carbonic acid, which will render four hundred cubic feet of atmospheric air unfit for respira

tion.

"A pound of oil produces 2.86 pounds of carbonic acid, and consumes the oxygen contained in 13.26 cubic feet of atmospheric air.

"A pound of coal-gas produces 2.56 pounds of carbonic acid, and consumes 4.25 cubic feet of oxygen, which is equivalent to that contained in 21.25 cubic feet of atmospheric air. For every cubic foot of gas burned, an equal quantity of carbonic acid is produced, and renders, according to Leblanc, 100 cubic feet of air unfit for respiration.

"As an illustration of the demand for air to produce efficient lighting, we may mention the following. In the vestry of a meeting-house in Boston, some years since, great complaint was made of the impurity of the oil used; it burned well for a time, when the lamps grew dim, and continued to grow more so through the evening. The sexton was directed to procure better; he tried many kinds, but all to no purpose. He had noticed, however, that, the longer he was compelled to remain after the services, and listen to the complaints of the aggrieved, the better his lamps burned, which was soon interpreted to mean the improvement of the air consequent upon the opening of the doors and the departure of the audience." - pp. 65-67.

The annoyance experienced in cities from smoke has always been complained of as very serious. So great is this grievance in London, that a member of parliament, a few years since, declared in his place, that it was well known that it had rendered the city uninhabitable. It has not yet attained to this formidable height with us, and probably the more general use of anthracite and wood than of bituminous coal will preserve us from the fate of London. Still, some method for burning smoke, where bituminous coal is used, especially in manufactories, has long been desired, and often attempted. If it has not yet been fully accomplished, the way seems at last to have been opened to it; and the following extract will indicate the principles involved, and the most successful practical results yet attained.

"We have already spoken of the great nuisance of the smoke of bituminous coal, as usually burnt in large cities. A great variety of modes have been invented and patents taken out for the consumption of smoke, but, until a short time, they have all been contrived upon a wrong principle. It has been supposed that it is only necessary to heat the smoke to a certain temperature to consume it, and if it is not consumed, it is because the requisite heat had not been attained. For this reason it was proposed, and the proposition was for a long time practised upon, to place the new coal in front, near the door, and allow the gases to be driven off over the hot coals and burn. This was Mr. Watt's plan; he admitted a quantity of atmospheric air where the coal. was undergoing the process of coaking, but never sufficiently dif fused to mingle with the gases and accomplish their complete combustion; even if they were transformed into carbonic acid, still, in passing over the incandescent fuel beyond, that carbonic acid would dissolve a portion of carbon and again become carbonic oxide. This plan was not successful, nor were any others which were formed upon the same principle.

"An Argand lamp without a chimney will burn without smoke, if the wick be kept low; but on raising it to a certain point, it smokes; if now the chimney be put on, the smoke no longer appears; it is not produced. In the first case, the volatilized carbon and disengaged hydrogen, into which the oil is converted, do not meet with sufficient air at a proper temperature until they have risen so high that they have become too cold to burn; in the second case, this amount of air is supplied at the right place, and the red-hot vapor of carbon unites with it and becomes invisible carbonic acid. This is precisely the principle upon which smoke is to be prevented in furnaces. Soft or bituminous coal is composed essentially of carbon and hydrogen, which, with a certain amount of heat, are disengaged as gases, and, if a proper amount of oxygen is supplied, and of a proper temperature, they unite with it and are consumed. If these facts are kept in view, it will be seen that smoke can be prevented as readily in the furnace as in the Argand lamp. If the air is introduced in too large quantity, or at too low a temperature, the gases are cooled, and smoke appears. In these cases, it is found necessary to admit the air heated to a proper temperature, without allowing it to come in contact with the fuel, and entirely separated from that which passes through the grate, that it may retain its full amount of oxygen up to the moment it mingles with the gases.

"It has been supposed that the admission of air would cool the furnace and diminish the amount of steam; but this is found not

to be the case when so regulated as just to consume the smoke, as will be seen in the following results of experiments by Mr. H. Houldsworth. The kinds of coal used were Knowles's Clifton coal, a free-burning kind, which does not cake, and produces a considerable quantity of ashes; and Barker and Evans's Oldham coal, a slow-burning, rich, caking coal, containing little ashes.* "Steam produced in a given Time.

Showing that the admission of air increases the amount of steam produced in a given time from 30 to 40 per cent."—pp. 105–107.

If it be difficult, with our present apparatus and methods of using fuel in our houses, to obtain all the economical advantages which would be possible from the combustion of smoke, we may obtain an equivalent for this waste, in saving our heat by an arrangement of double windows. Although we now and then see this arrangement adopted, we are confident that it deserves to be brought into more general use; and we have often wondered, that, with the laudable disposition to avoid all unnecessary expense, which is so general amongst our people, this simple fixture has been so much neglected. We know that the objection has sometimes been made to it, that the air of rooms thus guarded becomes less pure; that it preserves the heat mainly by preventing the escape of the warm, or the entry of the cold air. This is altogether a mistake, as the single window, if well fitted, prevents the passage of air, but fails to retain the heat, which can pass through a thin wall of glass with great facility. The nonconducting power of the double window, on the contrary, is well described by Dr. Wyman in the following paragraph.

"When a cold window makes a part of one of the walls, a constant current of cold air descends along it, which is often mistaken for that which enters the window from without; but it will exist without that, and cannot be prevented by closely fitted sashes, or any care in calking their crevices. The unpleasant effect of this fall of air from a number of large windows, as in churches, and their great influence in lowering the temperature of the room, are much greater than is usually supposed, especially in buildings

* Minutes of Evidence of Committee on the Smoke Nuisance, p. 122.

heated by warmed air, where the walls do not feel the influence of radiated heat. In our New England climate, where the temperature not unfrequently approaches zero, and is often below the freezing point, there would be a vast saving of heat, if our churches, court-rooms, and other public buildings, could be preserved from this cooling process. This can be done by means of double windows, fitting closely, and inclosing between them a quantity of air. Air, as is well known, transmits heat only by a change of position among its particles; each particle may receive a portion of heat from a heated body, and, by coming in contact with another less heated body, communicate its heat to it, but not otherwise. One particle never communicates its heat to another particle. Hence, if glass, or any other material which transmits light, be placed at two or three inches' distance from the glass, the inner sash will be kept warm, the circulation of the air between the sashes going on slowly; consequently, less heat will escape from the room. If this same arrangement were introduced into the walls of the room, and the transmission of air between them cut off at two or three levels in each room, or even if the communication between the different stories were completely cut off at the floor and ceiling, great good would result.* In buildings in which a complete system of ventilation is established, these windows should, as suggested by Count Rumford, be kept up both summer and winter. We say a complete system of ventilation, for, under such a system, windows would be required for the admission of light only, never for the admission of air. Double windows would, under such circumstances, in summer prevent the transmission of heat inwards, as in winter they prevent its transmission in the opposite direction. Glass is not necessary in the construction of double windows, where we require only a diffused light; white cotton, stretched upon a suitable frame, and rendered impervious to air by linseed oil or other preparations, will answer equally well for preserving heat, and be much less expensive." pp. 125–127.

Mr. Nathaniel J. Wyeth, of Cambridge, Mass., has adopted this principle in a brick ice-house which he has lately erected. The building is 198 feet long by 177 wide, and 40 feet high; the walls are 4 feet in thickness at the bottom, and 3 feet 6 inches at the top, including within their thickness two air-spaces. A triple wall is thus formed, the inner and outer being 8 inches in thickness, and that making the division between the two air-spaces 4 inches. The air-spaces are subdivided in portions of 6 feet in length and 5 in height; the first division being formed by bricks, and the second by planks resting on bricks projecting from the sides, and covered with dry tan. At the top and bottom of the building the air-spaces are made perfectly tight by masonry. The transmission of heat by the movement of the air is thus prevented, and the greater part of that which finds its way to the ice is by the radiation of the walls."

In any system of ventilation established and practised upon rational principles, it seems necessary first to determine what quantity of air is requisite to each individual in a given time. It would seem that the ration of air, the food to the lungs, might be assigned, like the ration of bread and meat, the food of the stomach, and although we might be required sometimes to content ourselves with a short allowance, it would be well to know what constitutes a full supply. To determine this question, various estimates and observations have been made, which exhibit widely discordant results. Dr. Arnott will be content with two or three cubic feet a minute; while the supply sometimes required in the House of Commons has been sixty feet a minute for each person. These extremes exhibit the difference between necessity and luxury. The smaller quantity will support life for the time, but with a constant feeling of discomfort and strain upon the health, while the larger gives a good tone to the body and a free flow to the spirits.

In cold weather, and it is then only that the amount of air need be limited, it will always be found, that, however large a quantity we may desire, we must bound ourselves by our wealth. The supply of heat required to warm a room is in proportion to the supply of fresh air admitted to it. Thus, while the rich may enjoy open flues and hot-air furnaces, those of more moderate means must content themselves with less costly modes of warming their rooms, and continue to use their atmosphere, as they do their garments, as long as possible.

It appears that the cost of high ventilation does not end with heating the air; for it has been found that a larger supply of food is consumed by a person kept constantly in a fresh atmosphere, than by one having less change of air. The following cases given by Dr. Wyman are in point.

"In a weaving-mill near Manchester, where the ventilation was bad, the proprietor caused a fan to be mounted. The consequence soon became apparent in a curious manner. The operatives, little remarkable for olfactory refinement, instead of thanking their employer for his attention to their comfort and health, made a formal complaint to him that the ventilator had increased their appetites, and therefore entitled them to a corresponding increase of wages! By stopping the fan a part of the day, the ventilation and voracity of the establishment were brought to a No. 133.

VOL. LXIII.

41