Numerical calculations give so good an idea of the utility of the inventions of our fellow-member, developement of some of the first ideas of Watt. Trace his labours, and, besides the points of principal importance particularly enumerated above, you will find him proposing engines to act without condensation; engines where, after having performed its office, the steam is dissipated in the atmosphere, intended for localities where there is a difficulty of obtaining cold water in abundance. The expansive principle, to operate in engines with several cylinders, will also figure among the projects of the Soho engineer. He it is who will be found to have suggested the notion of pistons perfectly tight, though composed exclusively of metallic parts ;-it is again Watt who will be seen first to have had recourse to mercurial barometers in order to ascertain the elasticity of the steam in the boiler and in the condenser ;-who devised a simple and permanent gauge by means of which the depth of water in the boiler may at any time be seen at a glance ;-who, to prevent troublesome variations of the level, connected the motions of the feed-pump with those of a float; -who, when it was much wanted, applied to a hole in the lid of the principal cylinder of the engine a little apparatus, the indicator, so contrived as to make the law of the evacuation of the steam be exactly known in its relations with the piston, [and to be a measure of the power,] &c. &c. Had time permitted me, I should have shown that Watt was no less skilful and successful in his attempts to improve boilers, to diminish the loss of heat, and to consume completely the clouds of black smoke which escape from ordinary chimneys, to whatever height they may be raised.-M. ARAGO. Mr. Watt, in his notes on Professor Robison, has stated his claim to the application of the crank, upon which he laid little stress, as he conceived it obvious to any one who considered the common foot lathe; and, in fact, it appears to have occurred to others, though probably unknown to him. To him we are unquestionably indebted for the beautiful contrivance of the sun and planet wheels, now little used, but of which we refer our readers to an excellent instance in the steam-engine of the brewery of Messrs. Whitbread and Co. in London, where it has been in successful operation for upwards of fifty years; and there are many others. The sun and planet wheels were adopted about the same time, 1786, in the engines of the great establishment of the Albion Mills, for supplying London with flour, which were destroyed by fire in 1791. See Mr. Watt's note on Robison, Mech. Phil. vol. ii. p. 137, and pl. v. in the same volume. Mr. Watt has there related, that that I cannot resist the desire of laying before you yet two other comparisons. I borrow them from one of the most distinguished correspondents of the Academy, Sir John Herschell. The ascent of Mont Blanc from the valley of Chamouni, is considered, and justly so, as the most toilsome undertaking that a man can perform in two days. Thus, the maximum of mechanical exertion, which we are capable of making in twice twenty-four hours, is measured by the raising the weight of our body to the height of Mont Blanc. This exertion, or its equivalent, a steam-engine will make, by consuming two lbs. of coal. Watt has, then, made it appear, that the strength which a man working for a day can exert, is no more than is contained in a lb. of coal. * Herodotus relates that the construction of the Great Pyramid of Egypt, occupied a hundred thousand men for twenty years. The Pyramid is built of calcareous stone; its cubic contents can be easily calculated; and hence the conclusion is drawn, that its weight is about thirteen millions of millions of lbs. To raise this weight to a height of a hundred and twenty-five English feet, the most valuable assistance in the planning and construction of the mill-work and machinery, was derived from that able mechanician and engineer Mr. John Rennie, then just entering upon business, under whose direction they were executed. They, indeed, formed an era in the history of practical mechanics, and of this country, by the introduction of improved machinery. We have pleasure in recording the intimacy and attachment, which continued through life, between that afterwards widely and justly celebrated civil engineer, and Mr. Boulton and Mr. Watt.-TR. * See Herod. Lib. II. cap. cxxiv.—Tr. height of the centre of gravity of the Pyramid, it would be necessary to burn, under the boiler of a steam-engine, six hundred and thirty chalders of coal. There is, among our neighbours, one foundry which I could name, which consumes a greater quantity of fuel every week. BY COPYING PRESS FOR LETTERS; HEATING Birmingham, when Watt went to settle at Soho, could reckon among the inhabitants of its neighbourhood, Priestley, whose name says everything; Darwin, the author of the Zoonomia, and of a well-known poem on the Loves of the Plants; Withering, an eminent physician and botanist; Keir, a chemist, distinguished by his Notes on his translation of Macquer, and by an interesting paper on the crystallisation of glass;* Galton, to * He was likewise the author of another paper in the Philosophical Transactions, on the congelation of the vitriolic acid; of a treatise on the different kinds of permanently elastic fluids or gases, in 1777 and 1779; and of a fragment of a Dictionary of Chemistry in 178990, as well as of an Account of the Life and Writings of the wellknown and eccentric philanthropist, Thomas Day, in 1791. Mr. Keir was a gentleman of great literary as well as scientific attainments, but preferred a life of retirement in the bosom of his family, and the society of a few friends, to the allurements of the fame which must have attended him in a more public life. Dr. Darwin had, we believe, removed from Birmingham to Lich whom we owe an elementary treatise on Ornithology; Edgeworth, the author of various works justly esteemed, and the father of Miss Maria, well-known to fame. Those learned men soon became the friends of the great mechanical philosopher, and nearly all of them formed an association, along with Boulton and him, under the name of the Lunar Society. So strange a name has given rise to extraordinary misapprehensions. The only meaning of it was, that the meetings were held monthly, on the evening of the full-moon, a period of the month which was fixed upon in order that the members [living in the country, on different sides of the town,] might have a light on their way home. Each meeting of this Society gave Watt a fresh opportunity of displaying that unrivalled fertility of inventive genius, with which he was by nature gifted. "I have formed an idea," said Darwin one day to his associates, " of a duplex pen, a pen with two quills, by help of which one may write two copies of anything; which will thus, at a single operation, produce both the original and the transcript of a letter." "I believe I can find a better way of solving the problem," rejoined Watt, almost immediately; " I shall think over it to-night, and communicate my ideas to you to-morrow." the morrow, the copying-press was invented; and even at that early period, a little model afforded the means of judging of its effects. This very field, before the formation of the Lunar Society, but came thence to attend the meetings with Mr. Edgeworth. It is honourable to Birmingham, then a small town, to have assembled such a constellation of talent in its vicinity.-TR. By useful machine, which has been so generally adopted in all the counting-houses in England, has recently received some modifications, the honour of which has been claimed by several artists; but I can assure you, that a description and drawing of it in its present form were given in our fellow-member's patent in the year 1780.* Heating by steam was three years later. Watt tried it in his own house, in the end of 1783. It is true that this ingenious plan had already been pointed out by Colonel Cooke, in the Philosophical Transactions for the year 1745;† but the idéa had been passed over unnoticed. Watt, at all events, deserves more than the credit of having * For a copy of Mr. Watt's specification of this patent, with engravings of the machines, see the "Repertory of Arts and Manufactures," vol. i. 1794, p. 13.-TR. + I read in a work of Mr. Robert Stuart, that Sir Hugh Platte had, before Colonel Cooke, conceived the possibility of applying steam to the heating of apartments. In the "Garden of Eden" of this author, published in 1660, there is in fact mention of some plan of this sort for keeping stove-plants through the winter. Sir Hugh Platte proposes to place lids of tin, or some other metal, on the vessels in which food is dressed, and then to adapt to holes in those lids, tubes through which the steam for heating may be conducted to any place where it is wanted.-M. ARAGO. For much important information on the subject of heating by steam, see Buchanan's "Treatise on the Economy of Fuel and Management of Heat, especially as it relates to Heating and Drying by means of Steam," in the preface to which, an account of Mr. Watt's proceedings in the application of this most useful principle, is given more in detail than anywhere else. A description of a machine for drying linen by steam, invented by Mr. Watt, was communicated by him to Dr. Brewster, read Dec. 21, 1824, before the Society for promoting the useful Arts in Scotland, and is to be found in the Edinburgh Encyclopædia, with an engraving copied from Mr. Watt's drawings; article STEAM DRYINg Machine.-Tr, |