21. Q. How is draft created through the fire?

A. Exhaust steam escaping through the stack reduces the pressure in the

smoke-box below the pressure of the atmosphere outside, therefore the

air tends to force itself into the smoke-box through all openings; with

everything in good condition, the easiest and largest passage for it is

through the grates and other openings into the fire-box and from it

through the tubes into the smoke-box and up the stack.