ISB 
Steam Engine^ 
of the smaller and the top of tlie larger cylinder, and ano» 
ther communication between the top part of both cylinders 
which last mentioned communication always i^emains 
open ; and let the top and bottom of the large cylinder 
also communicate by means of a side pipe ; and let the 
bottom part of the large cylinder communicate with a 
condenser. Things being thus arranged, when steam is 
admitting into the lower part of the smaller cylinder, the 
piston in that cylinder will ascend ; the communication 
between the top of the two cylinders being then open, to 
allow the steam above the smaller piston to pass into the 
top of the larger, where it is not to be detained, but, along 
with the steam above the piston in the large cylinder, to 
be allowed to pass under the last mentioned piston (which 
is now ascending as well as the piston in the smaller cy= 
linder), the communication between the two sides of the 
large piston being now open, and the communication with 
the condenser shut off. Both pistons having reached the 
top of their respective cylinders, the communications 
which before were open must now be shut (excepting the 
communication between the two cylinders at their upper 
part) and the communications between the bottom of the 
small and the top of the large, and between the bottom of 
the large and the condenser, must be opened : the steam 
last admitted into the lower paid of the smaller cylinder 
will now ascend into the top of the larger and expand 
itself, following the piston of the lai'ger cylinder which is 
now descending, its other side being open to the conden» 
ser ; and (as the tops of the two cylinders communicate) 
steam will also pass into the top of the smaller cylinder 
above its piston, so that both pistons descend together to the 
bottom of tlieir respective cylinders ; when a fresh charge 
of steam is again to be admitted for a fresh stroke of the 
engine. 
VoL IL A A 
