| Show that the ordinary innocent appearing telephones used in the underground depths of coal mines are capable of iob igniting n gas and thus bringing about disastrous mine explosions i is the novel fin finding dino of an investigation just conducted b by y the united stat states es bureau of mines at its experiment station at pittsburgh pa the dan danger daner er of gas as ignition and explosion does not exist in the employment of su such ch current as is necessary for talking over telephones autre but results from the ringing of the magneto |
