On Jul 26, 10:30*pm, harry wrote:

The only way I can think of determining water level without a sight
glass, would be by having trycocks above and below the aimed for water
level. *

The standard way for a very long time on stationary boilers was a
wooden float on the water level, linked through a wire or cord to the
outside. As pressures were low, leakage and mis-reading due to
pressure effects weren't a problem. This was used on ships too, but
was unsuccessful on locomotives (although it was tried), owing to the
float being shaken around - it worked when stationary though.