and fifteen feet wide, and drew 32 feet of water. He made several experiments with it, and it was in use fifteen months on the Saône.* 35.-In 1785 M. Perronet gave a very full description, in the French Encyclopædia, of an atmospheric engine erected near Saint Guilain, in Hainault; this description is remarkable for its clearness, and practical details, and not less so from its being introduced by stating Papin to be the inventor of the steam engine in a most unqualified manner; though admitting the first to have been constructed in England. 1788. Patrick Miller. 36.-About this time various competitors for the application of steam navigation appeared, (1785—88;) in America, two rivals; James Rumsey of Virginia, and John Fitch of Philadelphia. In Italy the application of steam power to vessels was proposed by D. S. Serratti, and in Scotland by Mr. Miller of Dalswinton, who afterwards on the sight of a model of a steam carriage invented by Mr. William Symington of Falkirk, was so much pleased with the model that he desired Mr. Symington to make him a small steam engine, to work a twin or double boat on Dalswinton Loch. The engine having been accordingly executed, and put on board the boat, the experiment was made at Dalswinton in the autumn of 1788, and it succeeded so well, that Mr. Miller commissioned Mr. Symington to purchase a gabert, or large boat, at Carron, and to fit up a steam engine on board of it, to make a trial on a larger scale. Every thing being completed, the trial was made on the Forth and Clyde canal, in the summer of 1789, Messrs. Miller, Stainton, Taylor, &c. being on board, and the result answered their most sanguine expectations; but most unaccountably, after having thus established, at a considerable expense, the practicability of employing the power of steam in navigation, Mr. Miller seems to have neglected it entirely.+ 37.-The theory of the steam engine still made sınall progress, though it excited some degree of attention. Bossut had described an atmospheric engine in the first edition of his Hydrodynamique, in 1771, with some formula for its statical equilibrium; in the edition of 1786, he investigated the proportion of counter weight, but for a particular case, and not including the actual circumstances of the moving forces. 38.-A rotary engine was proposed in 1789 by Cooke, and a patent was obtained for one in 1790, by Bramah and Dickinson,|| and for another in 1791 by Sadler. The * Dictionaire de Physique, art. Chaloupe à Vapeur. + Short Narrative of Facts relative to Steam Navigation, Edin. Phil. Journal. Repertory of Arts, Vol. III. p. 401. 1795. § Idem Vol. VII. p. 170. || Idem Vol. II. p. 73. peculiar construction of all these engines I need not describe, as the principle of a rotary engine will be shewn to be attended by a loss of effect, which mechanical combinations cannot remove. (See Sect. IV.) 39.-Bramah and Dickinson's patent included three varieties; the most simple of which is designed with pistons sliding in an eccentric wheel, the steam to enter at S; and the opening to the condenser being at C, the pressure causes the smaller wheel to revolve, and the pistons to slide in it. All the varieties are specimens of that beautiful FIG. 8. style of executing machinery which Bramah contributed so much to introduce in this country, and which has been carried to such high perfection by his pupil, the celebrated Maudslay. 1790. Bettancourt. 40.-Chev. Bettancourt, who was employed by the Spanish government to collect models of hydraulic machines, made a series of experiments on the force of vapour of water and of alcohol, at different temperatures. They are more accurate than those which were at that time before the public; but still had not that precision which is necessary to develope the laws of the force of vapour. He made a model of the double acting engine, with a new mode of forming the valves; and, Prony says, from merely seeing the exterior of a double acting engine when at work.* 1790. R. Prony. 41.-M. Prony is the author of one of the most extensive of the French works on the steam engine; it forms a part of his "Architecture Hydraulique," which commences in the first volume, and occupies nearly the whole of the second. * Archi. Hydraulique, Vol. I. p. 574. M. Prony begins with the properties of caloric, and the tables of Bettancourt on the force of vapour; and from the latter constructs empirical formula for calculating the force of vapour at different temperatures. These are not a little complex considering their want of conformity with experiment. He then proceeds to the description of engines as then constructed, and their parts; which are illustrated by plates having figures on a large scale. When he arrives at the parallel motion, the nature of the curve described by the extremity of the piston rod is very fully investigated, with tables to shew its variation from a straight line for a given range in the curve. It is followed by the proposal of a method for determining the diameter of the steam cylinder, which is little better than telling the artist to guess at it, and correct his guess by an intricate formula. The part on the steam engine terminates with a calculation of the effect produced by a given quantity of fuel, where the time of combustion is certainly erroneously introduced. The rest of the volume is occupied by an analytical investigation of empirical formula for the expansive forces of elastic fluids and vapours at different temperatures, which has been rendered wholly useless by later researches having shewn the experiments to be in accurate It is remarkable that Prony had not acquired a knowledge of the advantage of steam acting expansively; though when his second volume appeared, it had been fifteen years a contested discovery in England. Of his labours it may be said, that they afford the strongest evidence that mere mathematical talent is not sufficient for the promotion of mechanical science, otherwise the principles of the steam engine would not have remained to be investigated. 1795. John Banks. 42.-Mr. Banks, in a work on mills, published in 1795, has treated of the maximum of useful effect in atmospheric steam engines. He considers the space, or length of the stroke, the given quantity, in which his investigation differs from those of Blake and Emerson. He has, however, by considering the atmospheric pressure as a gravitating weight, failed in giving a correct solution. One of his problems includes the weight of the moving parts of the engine; and he adds some useful practical formulæ for the statical equilibrium of engines for raising water, with examples.' In 1803, Mr. Banks gave some rules for the strength of engine beams, both for wood and cast iron; and also a description of a gauge for determining the state of rarefaction in the cylinders and condensers of steam engines, in principle the same as the common barometer; and differing from the ordinary condenser gauge by having a cistern instead of a syphon for the mercury. His rules for the strength of beams are to find the relation between the F peculiar construction of all these engines I need not describe, as the principle of a rotary engine will be shewn to be attended by a loss of effect, which mechanical combinations cannot remove. (See Sect. IV.) 39.-Bramah and Dickinson's patent included three varieties; the most simple of which is designed with pistons sliding in an eccentric wheel, the steam to enter at S; and the opening to the condenser being at C, the pressure causes the smaller wheel to revolve, and the pistons to slide in it. All the varieties are specimens of that beautiful style of executing machinery which Bramah contributed so much to introduce in this country, and which has been carried to such high perfection by his pupil, the celebrated Maudslay. 1790. Bettancourt. 40.-Chev. Bettancourt, who was employed by the Spanish government to collect models of hydraulic machines, made a series of experiments on the force of vapour of water and of alcohol, at different temperatures. They are more accurate than those which were at that time before the public; but still had not that precision which is necessary to develope the laws of the force of vapour. He made a model of the double acting engine, with a new mode of forming the valves; and, Prony says, from merely seeing the exterior of a double acting engine when at work.* 1790. R. Prony. 41.-M. Prony is the author of one of the most extensive of the French works on the steam engine; it forms a part of his " Architecture Hydraulique," which commences in the first volume, and occupies nearly the whole of the second. Archi. Hydraulique, Vol. I. p. 574. M. Prony begins with the properties of caloric, and the tables of Bettancourt on the force of vapour; and from the latter constructs empirical formula for calculating the force of vapour at different temperatures. These are not a little complex considering their want of conformity with experiment. He then proceeds to the description of engines as then constructed, and their parts; which are illustrated by plates having figures on a large scale. When he arrives at the parallel motion, the nature of the curve described by the extremity of the piston rod is very fully investigated, with tables to shew its variation from a straight line for a given range in the curve. It is followed by the proposal of a method for determining the diameter of the steam cylinder, which is little better than telling the artist to guess at it, and correct his guess by an intricate formula. The part on the steam engine terminates with a calculation of the effect produced by a given quantity of fuel, where the time of combustion is certainly erroneously introduced. The rest of the volume is occupied by an analytical investigation of empirical formula for the expansive forces of elastic fluids and vapours at different temperatures, which has been rendered wholly useless by later researches having shewn the experiments to be in accurate It is remarkable that Prony had not acquired a knowledge of the advantage of steam acting expansively; though when his second volume appeared, it had been fifteen years a contested discovery in England. Of his labours it may be said, that they afford the strongest evidence that mere mathematical talent is not sufficient for the promotion of mechanical science, otherwise the principles of the steam engine would not have remained to be investigated. 1795. John Banks. 42.—Mr. Banks, in a work on mills, published in 1795, has treated of the maximum of useful effect in atmospheric steam engines. He considers the space, or length of the stroke, the given quantity, in which his investigation differs from those of Blake and Emerson. He has, however, by considering the atmospheric pressure as a gravitating weight, failed in giving a correct solution. One of his problems includes the weight of the moving parts of the engine; and he adds some useful practical formulæ for the statical equilibrium of engines for raising water, with examples.' In 1803, Mr. Banks gave some rules for the strength of engine beams, both for wood and cast iron; and also a description of a gauge for determining the state of rarefaction in the cylinders and condensers of steam engines, in principle the same as the common barometer; and differing from the ordinary condenser gauge by having a cistern instead of a syphon for the mercury. His rules for the strength of beams are to find the relation between the F |