and marine engines.

In a compound engine the steam first enters the small or high pressure
cylinder and is then exhausted into the large or low pressure cylinder,
where the expansive force is all obtained.

Two cylinders are used because we can get better results from high
pressure in the use of two cylinders of different areas than by using
but one cylinder, or simple engine.

That there is a gain in a high pressure, can be shown very easily:

For instance, 100 pounds of coal will raise a certain amount of water
from 60 degrees, to 5 pounds steam pressure, and 102.9 pounds would
raise the same water to 80 pounds, and 104.4 would raise it to 160
pounds, and this 160 pounds would produce a large increase of power over
the 80 pounds at a very slight increase of fuel. The compound engine
will furnish the same number of horse power, with less fuel than the
simple engine, but only when they are run at the full load all the time.

If, however, the load fluctuates and should the load be light for any
considerable part of the day, they will waste the fuel instead of saving
it over the simple engine.

No engine can be subjected to more variation of loads than the traction
engine, and as the above are facts the reader can draw his own
conclusions.

FRICTION CLUTCH