“The Turkish ladies express horror at seeing Englishwomen so tightly laced.” (Lady M. W. Montague.) See Distortions.

STEAM. The application of steam of the laboratory, as a source of heat, is commonly

effected by means of double pans, to the space between which steam, at a moderate pressure, is introduced, the arrangements being such as to permit of the condensed steam, or distilled water, being removed, by means of a cock, nearly as soon as formed, or as may be desirable. Another plan is to place coils of metal pipe along the bottom of cisterns, vats, &c., formed either of wood or metal, and to keep them supplied with high-pressure steam.

“It is quite susceptible of positive proof that by no arrangement yet discovered, can more than two thirds of the heat generated by a given quantity of coal, during combustion, be fairly absorbed and utilised in any of our manufactories; and, moreover, there are undeniable facts, which demonstrate that seldom, in the burning of coal, are more than three fourths of the total heat, which might be eliminated, actually obtained; thus justifying the supposition that one half of all the coal now consumed is virtually wasted and lost to society.” To lessen, as much as possible, this loss various improvements have been made, “which, for the most part, have consisted in lengthening the flues, and exposing a larger surface of the boiler to the action of the heated air passing from the furnace to the chimney.” “Remembering that air is an extremely bad conductor of heat, and that water about to be converted into steam is also a bad conductor, it is evident that time must form an important element in the perfect transmission of heat from one of these to the other; and hence, with a great velocity of current existing in the flues, very little heat would pass from air, however high its temperature, to water contained in a boiler, and so circumstanced with respect to its all but gaseous condition.” The results of the experiments on fuel made at the Museum of Practical Geology by Sir H. de la Beche and Dr Lyon Playfair go clearly to show that “to open the damper of a steam-boiler furnace is pretty generally to diminish the effective power of the fuel.” “Great waste of coal now arises from this simple circumstance; and much of the heat of the fire, which ought to go to the boiler, is lost by its (too) hasty transmission up the chimney. If, however, there be thus far room for improvement in the direction just indicated, still wider is the vacant space, caused by imperfect combustion, or, in technical phrase, ‘bad stoking,’ merely because the stoker, to economise his labour, and to avoid trouble, throws on to the bars of his furnace a thick layer of fuel, by which loss is caused in two or three directions.” These are, principally, imperfect combustion, and the volatilisation of fuel, as smoke, &c., from an insufficient supply of air, and from a mass of mere red-hot coke or cinder, two or three inches thick, lying between the boiler and the hottest part of the furnace; which last, according to Dr Kennedy, is about one inch above the fire-bars. Besides which, “in passing over

this red-hot coke, the carbonic acid would be converted into carbonic oxide, and thus not only remove a quantity of carbon equal to its own, without yielding any additional heat, but actually with the production of cold, or, in other words, the absorption of heat.” (‘Dict. Arts, Manuf., and Mines.’) This points to the evident policy of using a smoke-consuming furnace, as noticed elsewhere.

Another matter worthy of remark is the constant waste of heat, and, consequently, of fuel, in laboratories and manufactories in which steam is employed, owing to the exposed condition of the pipes, boilers, and pans. All of these should be well ‘clothed’ or covered by some non-conducting medium, to prevent loss of heat by radiation, and by contact with the atmosphere. Not only does economy dictate such a course, but the health and comfort of the workpeople demand that the atmosphere in which they labour should be as little heated and poisoned as possible.

Table of corresponding Pressure and Temperatures of Steam. By Arago and Dulong.

Pressure in Atmospheres.[194]Temperature, Fahr.Pressure in Atmospheres.[194]Temperature, Fahr.
Degrees. Degrees.
1212·13380·66
11⁄2234·14386·94
2250·515392·86
21⁄2263·816398·48
3275·217403·83
31⁄2285·18408·92
4293·719413·78
41⁄2300·320418·46
5307·521422·96
51⁄2314·2422427·28
6320·3623431·42
61⁄2326·2624435·56
7331·725439·34
71⁄2336·8630457·16
8341·7835472·73
9350·7840486·59
10358·8845499·14
11366·8550510·6
12374·

[194] Estimating 14·6 lbs. = 1 atmosphere.

A cubic inch of water, during its conversion into steam, under the ordinary pressure of the atmosphere, expands into 1696 cubic inches, or nearly a cubic foot.