1822.] Mr. Partington on the History of the Sieam Engine. 59 
model, capable of producing a force equal to 14 pounds on every 
inch of the piston, and which did not require more than one- 
third of the steam used in the common atmospheric engine to 
produce the same effect. 
“Jt will be evident that this was as near an approximation 
towards perfection as could possibly have been expected ; and 
indeed much more than was likely to be effected in a large 
engine, as the vapour left beneath the piston possessed only 
1-15th part of the elastic force of the steam employed to form 
the vacuum. 
“Having discovered that the great waste of caloric in the old 
engine, arose from the alternate heating and cooling the cylin- 
der, by the admission and subsequent condensation of the 
heated steam, Mr. Watt perceived that to make an engine in 
which the destruction of steam should be the least possible, 
and the vacuum the most perfect, it was necessary that the 
cylinder should remain uniformly at the boiling point; while 
the water forming the steam was cooled down to the tempera- 
ture of the atmosphere. To effect this, he employed a separate 
condensing vessel, between which, and the hot cylinder, a 
communication was formed by means of a pipe and stop cock. 
“To understand the action of this engine, we may employ a 
common syringe, connected with a boiler, as in the atmo- 
spheric engine, and furnished with a pipe passing into an air- 
tght vessel, immersed in water for the purpose of condensa- 
tion. 
“If the piston be then raised, and the communication with the 
condenser cut off, the steam will speedily expel the air ; when 
this is effected, the further admission of steam must be pre- 
vented, and the communication with the condenser opened. 
The steam wii! now expand itself, passing down the pipe and 
entering the condenser; the moment, however, that it comes in 
contact with the sides of the cold vessel, it will be condensed 
and a vacuum formed ; and this process will continue to proceed, 
so long as any steam remains beneath the piston. 
** The only objection that offered itself to this admirable mode 
of condensation, arose from the difficulty experienced in get- 
ting rid of the water and air that remained in the condensing 
vessel. When steam was generated from water that had been 
freed from air by long boiling, a considerable advantage was 
obtained ; and it was found that a power nearly equal to the 
entire pressure of the atmosphere was produced. The great 
advantage thus obtained will be sufficiently obvious, when it is 
known that, in the engines previously constructed, the elasticity 
of the steam arising from the heated injection water remaining 
at the bottom of the cylinder, was equal to one-eighth of the 
atmospherical pressure, and consequently destroyed an equal 
proportion of the power of the engine. ; 
- ‘©The mode of condensing the’ steam, by the application of 
