AN ACCOUNT OF THE STEAM ENGINE.

For the purposes of this article, I have consulted the following essays.

1st. The articles steam, and steam engine, in the old Edinburgh Encyclopedia, republished in this country by Dobson. I believe these articles were drawn up by Professor Robison, of Edinburgh, and are well executed. As this work is common in America, I have not chosen to copy these articles, but I earnestly recommend them to the careful (not the perusal, but) study of the reader who wishes to become acquainted with this subject. In studying these articles, care must be taken to refer to the additions made in the supplement to that Encyclopedia, under the head of,, Steam engine."

2dly. An account of steam engines, by Olinthus Gre gory, the compiler of Gregory's Encyclopedia, a work for the most part too brief and superficial to communicate valuable knowledge: but the mechanical articles are tolerably well executed, it being a subject to which he had much attended. The account of steam engines is extracted from his treatise on mechanics, theoretical, practical and descriptive. Second edition, 1807. The artiVol. II.

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cle is chiefly drawn up by Mr. J. C. Hornblower, who had a law suit with Mr. James Watt, of Birmingham, wherein the latter was plaintiff, on the subject of infringing the patent right of Mr. Watt. Mr. Hornblower was cast. The article in Gregory, is drawn up with so much illiberality of remark on the pretensions of Mr. James Watt, and on the article in the Edinburgh Encyclopedia above referred to, that I have been able to make a few extracts only from it, for the use of the Emporium. This tract of Gregory's induced

3dly. A review of Gregory's account steam engines, in the 26th number of the Edinburgh Review, for January 1809. This very able and very severe article, I have been, given to understand, was written by Professor Playfair, of Edinburgh, whose very brief but very neat account of the history of steam engines, I shall extract.

4thly. I have consulted, and shall use, Nicholson's account of Watt's steam engine in his 8vo. Encyclopedia ; a work, written under the pressure of straitened circumstances, and therefore not with the usual care of this most useful and industrious man.

5thly. I have consulted the following articles on the subject in Nicholson's Journal, viz. 1 V. 419. 2 V. 46 228. 364. 476. 3 V. 86. 161. 4 V. 545. 5 V. 147. of the quarto edition. Of the 8vo. series, 1 V. 161. 2 V. 68. 6 V. 218. 249. 7 V. 310. 8 V. 169. 262. 11 V. 93. 243. 12 V. 1. 174. 294. 316. 17 V. 5. 18 V. 260. And the following articles in that collection on horse power, 9 V. 214. 11 V. 96. 98. 145. 264. 271.

I have also consulted the articles giving an account of Cartwright's, Trevethic's, and Woolfe's improvements on Watt's engine in Tilloch's Philosophical Magazine, wherein the articles relating to the steam engines, are to be found in 1 V. 1. 16 V. 372. 17 V. 40. 164. 19

V. 133. 275. 21 V. 254. 23 V. 123. 335. 23 V. 123. 335. 26 V,

316.

As there is no general index to these works, I apprehend it will be useful to note the places where information on this subject can be found in them.

The common histories of the steam engine, include a description of Savary's, Newcomen's and Cawley's, and Watt's. I shall add, some account of the improvements of Hornblower, Cartwright, and Woolfe. Also, Oliver Evans's account of his steam engine. I do not know that I can get all the plates ready for the present number, but I shall insert herein the methods of consuming smoke, because those plates are likely to be completed in time.

On the means of CONSUMING THE SMOKE, arising from large furnaces, particularly from steam engines. I would premise, that smoke, is a mixture of aqueous vapour-charcoal--and carburetted hydrogen, distilled off by means of heat from fuel.

When a candle or a lamp burns in the common me. thod, they smoke. That is, the fuel instead of being burnt or consumed, is in part distilled away by the heat: for as there can be no combustion but by means of the oxygen of the atmospheric air, and as the outside only of the wick is in contact with the air, the fuel with which the outside is impregnated, only can be burnt: the oil or tallow of the inside, is distilled away and forms the smoke. Part of this is caught and inflamed as it escapes into the air; hence the flame of a candle extends beyond the point of the wick; but the whole of it is not burnt. What is not burnt is smoke.

To remedy this M. D'Argand, the inventor of the patent lamp, has contrived (by making the wick thin, and circular, and by admitting a current of air to both sides of the wick) to consume the whole of the fuel by supplying every part of it with atmospheric air in a strong cur.

rent occasioned by the rarefaction produced in the glass chimney. That this is a true account of the process, any one may satisfy himself, by closing the apertures of the grating at the bottom of the lamp, through which the air ascends up the chimney; and the wick no longer supplied with the oxygen of the atmosphere, will send off the combustible oil, unburnt in the form of smoke like a common lamp.

If a piece of wood be distilled, it furnishes an acidulous watery liquor, a large quantity of carburetted hydrogen gas, that is charcoal dissolved in hydrogen gas, and its own bulk of charcoal. Both the hydrogen gas and the charcoal, are combustible with access of air, but incombustible without it. The flame of a wood fire, is owing to the ascension of the carburetted hydrogen distilled off from the wood. The smoke is partly acidulous vapour, and partly unconsumed carburetted hydrogen.

Whatever is capable of being burnt gives out heat : for the oxygen of the atmosphere, when it combines with a combustible body, parts with the heat to which it is chemically united. That heat, becomes sensible, and acts upon the bodies around. The smoke attaches itself to the bodies it meets with, and sticks to them, and a quantity of earbon or charcoal is deposited: this mixture is called Soot.

When a quantity of coal is set on fire the same process takes place; a tar-acid vapour flies off mixed with carburetted hydrogen holding much carbon or charcoal in solution; this is the smoke, which when condensed in the chimney or on the bottom of a boiler, forms also soot; thicker, and containing more carbon, and volatile oil than the soot of wood.

Four ounces avoirdupois of pine saw dust, yielded me 12 quarts of carburetted hydrogen. The same weight of bituminous Liverpool coal, yielded me 18 quarts. Some