SECT, i.] THE STEAM ENGINE. . 29 



a few corrections of Dr. Robison's article in his 'Mechanical Philosophy,' and several 

 notes to it, containing his experiments on the latent heat and elastic force of steam. 



30. The share which Boulton had in the improvement and introduction of 

 the steam engine must not be forgotten ; for as it has been remarked by Baron 

 Dupin, " Watt's engine was, when invented by him, but an ingenious speculation, 

 when Boulton, with as much courage as foresight, dedicated his whole fortune to 

 its success." He did not hesitate even when Smeaton declared his conviction that 

 it could never be generally applied as a useful agent. Besides, Boulton rendered 

 no small service to Watt and to Great Britain, when, by his extraordinary talents 

 in manufactures and commerce, he exempted his partner from all the cares of life, 

 from all commercial speculations, and from all those difficulties which are the 

 inevitable consequences of great enterprise in trade. Boulton did still more ; he 

 triumphed over all those interests and prejudices which necessarily arose in the 

 beginning to retard the success of the new steam engines and their application. 

 " Men," continues Dupin, " who devote themselves entirely to the improvement 

 of industry, will feel in all their force the services that Boulton has rendered to the 

 arts and mechanical sciences, by freeing the genius of Watt from a crowd of extra- 

 neous difficulties, which would have consumed those days that were far better 

 dedicated to the improvement of the useful arts." 



31. A curious apparatus for trying the elastic force of different vapours was 

 invented by T. H. Zeigler, which he describes in a memoir published at Basle in 

 1769, with tables of the results of his experiments; but it appears he had not taken 

 care to free his apparatus from air before the trials ; they are therefore useless. 



1781. JONATHAN HORNBLOWER. 



32. In 1781, a patent was obtained by Mr. Hornblower, for a mode of apply- 

 ing the expanding power of steam. For when steam is confined on one side of 

 a piston, and a partial vacuum is formed on the other, the steam will move the 

 piston till its force be in equilibrium with the friction and uncondensed steam ; 

 and as much power as is communicated during this motion is in addition to the 

 ordinary effect of steam pressure. To gain power in this manner, Mr. Hornblower 

 used two vessels in which the steam was to act, and which, in other steam engines, 

 are called cylinders, employing the steam after it had acted in the first vessel to 

 operate a second time in the other, by permitting it to expand itself, which he did 

 by connecting the vessels together, and forming proper passages and apertures, 

 whereby the steam might at proper times go into and out of the said vessels. l 



1 Repertory of Arts, vol. iv. p. 361. 1796. 



