Volcanoes Under Cities

A terrific explosión recently occurred in broad daylight, in the most thickly thronged portion of a New York city street. Huge paving stones and the heavy iron covers of several "manholes" were hurled ten feet into the air. Fortunately no one was hurt seriously. But like explosiona have takon place several times in New York and elsewhere. The liability of their rocurrence must be born in miud constantly, in tho present effort to bury electric wires. The explosión in New York was f rom a subway which the board of electrical control are constructing to convey telegraph, telephone and electric wires of all kinds under ground. But the 8ubway is not yet completed, and there was no electrical current passing through the wires it contained. They have uot yet been connected. Much inquiry has been made to ascertain the causes of snch explosions. With the vast array of dynamos, electrical wires and machines, with the return currents f rom all of them passing through the eartib, the ground beneath our large cities must be tremendously charged with electricity ai all times. Positive and negativo currents pass and repass and cross. With these there must be at times leaping charges at the fluid, like lightning from a cloud. If an explosiva gas is in the track of the current it wil] naturally take fire with tremendous force. There is always more or less underground leakage of both sewer gas and Uluminating gas. It has been suggested that ventilating pipes would allow thia tj escape harmlessly.