BOILERS, FUELS AND FLUES 217 



Fig. 115. Steam guage 



is screwed into a hole in the boiler near 

 the bottom. If the water level falls below 

 the plug the heat melts it out, thus making 



Fig. 116. Diagram of automatic damper regulator. The 



steam pressure acts against a flexible diaphram which 



is connected with the dampers by means of a lever and 



chain 



