203 
Steam Riigine. 
Oliver Eva^^s’s Columbian Steam Engine. 
Explanation, 
A, the boiler~B, the working cylinder — C, the lever 
beam — -D, the fly-wheel— E, the condenser — F, the Ava^ 
ter-pump — G, the supply pump— H, the furnace— I, the 
chimney flue— K, the safety-valve, which may be loaded 
with 100 or 150/6^. to the inch area ; it tvill never need 
more, and it must never be fastened down. 
Operation. 
The boiler being filled with pure water as high as the 
dotted line, and the fire applied, the smoke enters the cen- 
tre flue which passes through the centre of the water to 
ascend the flue I, and thus acts on a large surface. 
When the steam lifts the safety-valve, it is then let into 
the cylinder by opening the throttle- valve, to drive the 
piston up and down, which, by rod 1, gives motion to 
the fly-Avheel, and wheel 2 gives motion to a shaft, pass^^ 
ing through the posts, to turn the spindle of the rotary- 
valves 3, 8, which lets the steam both off* and on the cy- 
linder at the proper time. 
The steam escaping by pipe 4, curved and immersed in 
the water in box E, which is supplied by pump F, it is 
condensed, and the water formed, descends by pipe 5, into 
supply pump G, and is forced into the boiler again by 
pipe 6. 
But boiling decomposes Avater slowly changing it into 
air incondensible. Therefore the shifting- valve 7, is ne- 
cessary. This valve lifts at every puff of steam, and a 
small quantity of air escapes ; and it shuts, and a vacuum 
is instantly formed, as the crank passes the dead points. 
The small waste of AA^ater may be supplied by condens- 
ing part of the steam rising from the condensing Avater, to 
run doAvn the pipe 9, through a hole in the key of a stop^ 
