346 Mr. J. Trowbridge on the Oscillations of 



decompose the water with great evolution of the gases ; and 

 it is probable that an ordinary discharge of lightning of a 

 few hundred feet in length could light for an instant many 

 thousand incandescent Tamps if it were properly transformed 

 by means of a step-down transformer. Indeed the ringing 

 of electrical bells and the melting of electrical fuses are of 

 common occurrence during thunderstorms, and manifest the 

 energy of lightning discharges. During a recent visit at a 

 summer hotel which was lighted by incandescent lamps, I was 

 much interested to observe that the lamps blinked at every 

 discharge of lightning, although the interval which elapsed 

 between the blinking and the peals of thunder showed that 

 the storm was somewhat remote. This effect was doubtless 

 due to induction produced by the surgings of the lightning 

 discharges ; for in heavy and in near discharges the lights 

 were completely extinguished, although no fuses were burned. 

 My observation of this effect of lightning upon electric- light 

 circuits also leads me to believe that the system of carrying 

 electric-light wires along gas-fixtures, where both electric-light 

 fixtures and gas fixtures are combined, is fraught with great 

 danger. If there is any leakage of gas at the joints of the gas- 

 pipes or through a sand-hole in the casting of the pipes, electric 

 sparks, arising through resonance effects or from the ordinary 

 passage to earth of an electric charge brought into the building 

 by the electric wires, can ignite the escaping gas and produce 

 a n^sterious conflagration. Such a conflagration was averted 

 in the hotel in which I noticed the blinking of the lamps only 

 by the careful scrutiny of an attendant, who noticed a jet of 

 gas from a pin-hole in the gas fixtures impinging on the 

 woodwork. During the storm a minute electric spark had 

 ignited the escaping gas. Electric-light wires and gas-pipes 

 should never be contiguous, for no lightning-guard or pro- 

 tector can ensure that minute sparks, due in some cases to 

 resonance effects, may not arise. 



The study of the disruptive or oscillatory discharge of 

 lightning is closely related with that of the brush- discharge 

 and the phenomenon of the Aurora Borealis ; for the disrup- 

 tive discharge ceases to be disruptive after a few hundred- 

 thousandths of a second — as figures 1 and 2 show— and par- 

 takes of the nature of a brush-discharge. The zigzag fissure 

 in the air disappears, and only the spark- terminals glow. 

 Recent experimenters have exhibited as a marvel the lighting 

 of a vacuum-tube through the human body by grasping one 

 terminal of a suitable transformer with one hand and by 

 holding the vacuum-tube in the other hand. It must be 

 remembered, however, that the lines of force proceed from 



