Description o/’Mr Perkins’s New Steam-Engine . 175 
reaches the piston ; and, consequently, that this engine is no- 
thing more than a High Pressure Engine. Other persons, how- 
ever, have supposed, and we confess we are among that number, 
that the portion of water which escapes, must necessarily carry 
off a quantity of heat from the adjoining stratum (the tempe- 
rature of which may be thus reduced below the freezing point). 
But it is more likely, that, in virtue of some new law of the 
transmission of heat under the combined conditions of elevated 
temperature and high pressure, while the water, also, is forced 
to remain in contact with the red hot generator, the whole water 
in the boiler may be laid under requisition to furnish the dis- 
charged fluid with its necessary supply of caloric. 
It is almost unnecessary to state, that the motion of the engine 
is produced by the difference in elasticity between the steam press- 
ing on one side of the piston and that pressing on the other. In 
the first case, the steam recently produced, acts with a force, 
say of 500 lb. on the square inch, while that on the weak side, 
or that communicating with the condenser, acts with only 70, 
the difference, or 430 lb., being the true power gained. 
When there is a surplus of water in the generator, occasioned 
either by working the forcing pump too violently, or by too vehe- 
ment a heat, the water will escape by the tube m with a valve 
above, loaded with 37 atmospheres, and will pass by the pipe 
5, 5, 5, into the condenser STXV. 
In order to explain the ingenious manner in which the pipe 
4, 4, 4 supplies the generator with water, we must observe that 
this pipe communicates with the pump L, which is wrought by 
the engine. This pump draws the water by the pipe 6, 6, 6, 
from the condenser STXV, and returns it by the pipe 4, 4, 4 ; 
that is to say, when the handle M is drawn up, the water rushes 
into the cylinder of the forcing pump, through a valve in the 
pipe 6, 6, 6, opening into that cylinder : This valve, of course, 
instantly closes when the downward stroke of the pump is made, 
and the water now escapes through a valve opening outwards , 
along 4, 4, 4 ; thus effectually cutting off all direct or uninter- 
rupted communication between the generator and the condenser. 
In order to keep the water in the condenser at a pressure of five 
atmospheres, the blast of the bellows H goes round the con- 
denser STXV ; but, when it is not sufficient for this purpose. 
