380 
Steam Engine^, 
out the air, which always, to a certain degree, accompa- 
nies the steam, and by its elasticity re-acts against the un- 
der side of the piston. 
He keeps the outside of the working- cylinder, hot, by 
the intervention of steam between it and a casing. 
He contrived the parallel motion, by which the piston 
and the upright rod attached to it and connected with the 
bealn, preserves its perpendicularity during the stroke. 
He depressed the piston by letting in steana above and 
upon it, instead of leaving it to descend by the pressure 
of the atmosphere, thus doubling the duty performed by 
the steam, and gaining in power and frequency of stroke. 
He kept the top of the piston, hot, by means of a casing 
between the piston and the outward air; so that the steam 
let on above, is always of the same temperature with that 
let in below the piston. 
He consumed the smoke of the fuel, by making it pass 
through and over the red hot coals : thereby converting 
the carbon and the carburetted hydrogen of the smoke in- 
to fuel ; and preventing the bottom of the boiler from be- 
ing covered with soot, which is a non-conductor of heat. 
He supplied the boiler with the hot-injection water. 
He applied two pipes or tubes inserted into the boiler 
at different depths ; and furnished with cocks ; by means 
of which, it can be ascertained when the boiler is too full, 
by its throwing out water, or too empty, by its throwing 
out steam. 
He improved the method of letting the hot-injectioii 
w^ater into the boiler as need requii'ed, by opening the 
valve with a floating stone instead of the ball-cock. 
He first gave perfection to the rotatory motion by the 
Sun and Planet wheels connected with the fly. 
He sedulously aimed at perfection in every part of the 
W'Orkmanship of the engine, which in his case becam<« 
much superior to any antecedent engine. 
