1891.] 



testing the Sensitiveness of Safety-lamps. 

 FIG. 1. 



123 



Fro. 2. 



tube below. It had a plate-glass window in front for observing the 

 lamp in the interior, and a flanged opening below for introducing the 

 safety-lamp. This opening was closed by a water-seal consisting of a 

 small zinc tray supported by buttons, and containing about 2 inches 

 depth of water, into which the flange dipped. A mixer was arranged, 

 which consisted of a light flat board, nearly equal in dimensions to the 



