=The Exhaust Nozzle=, as generally constructed, is an elbow attached
to the end of the exhaust pipe in the smoke box or smoke stack of the
boiler, the end of which points upward, with the opening reduced so
that the exhaust steam will be forced up the stack, and thereby produce
the same effect as a blower.
The opening in the exhaust nozzle should never be made so small as to
check the exhaust steam to any great degree, and cause back pressure
in the cylinder, as the power of the engine would be diminished. The
opening should be as large as possible, and still produce sufficient
draught to keep the required steam pressure.