io the Boilers of ordinary Steam-Engines. 333 
merely for the purpose of safety; and at the end of itthere . 
is an apparatus f, attached, by which the pressure is indica- 
ted; g, is the feeding or injecting pipe leading from the for- 
cing pump h, which may be worked by a connexion to the 
moving part of the engine. 
‘In order to generate steam, the vessel a must be filled 
with water, or other fluid or fluids, from the pump A, and 
heated by a furnace, or otherwise: the steam, or escape- 
valve b, being loaded by means ofa weight, with a pressure 
greater than the expansive force of the steam, to be genera- 
from such water, or other fluid or fluids, at the time of 
its generation. When tlie water, or other fluid or fluids, in 
the generator, has attained the necessary degree of heat, say 
from 400 to 500 degrees of Fahrenheit, more or less, an 
additional quantity of a Pion: or fluids, is 
pumped into the generator, ient to out a portion 
of ‘209 already heated in the generator from under 
weighted-valve 6, into the steam-pipe d, where it instantly 
beeomes steam. : : 
“ An enlarged representation of the valve, and its seat, is 
shewn in the section, Fig. 2. The valve is a spherical 
bulb, falling into a concave seat, in the lower part of the 
square chamber ; the upper part of the valve is a cylindrical 
tod, upon the top of which the weight of the pressing-lever 
is exerted ; the lower part of the valve is a triangular ; 
sliding up and down the cylindrical passage. When the ad- 
ditional quantity of water is injected into the generator, by 
means of the force pump as described, the bulb of the 
where the pressure no longer operating upon that portion of 
the water, it immediately becomes steam, and passes forward 
