282 Messrs. J. Trowbridge, T. C. and I. C. Howe on the 



connexion and employed a spark-gap having a range from 

 zero to 80 centimetres. It was possible to still further extend 

 this range to 200 centimetres; but it was found that the 

 range from zero to 80 centimetres exhibited the main 

 features of the phenomenon. The preceding table gives the 

 results obtained with discharges produced by three million 

 volts. 



It will be seen from the curve A (fig. 2) that the explosive 

 effect increases closely proportional to the length of the spark 



Fig. 2. 



/V 



L V 



/ s 



t \ 



I v 



i ^ 



i 



1 



t 



* 



/ 



T ' 



r 



~i 



~t 



~l_ 



_j 



7 



t 



r 



J-^ 



^t ^^ 





1 



until the length of 50 centims. is reached. It then begins 

 to diminish. This decrease occurs with the increase of 

 electrostatic effect in the field surrounding the spark-gap — 

 or, in other words, with the divergence or spreading of the 

 electric lines of force. The electrostatic effect in this field 

 when a difference of potential of three million volts is gene- 

 rated is very great. Sparks can be drawn from neigh- 

 bouring objects. Shocks are felt when the observers touch 

 each other ; and photographic plates, shielded from light in 

 plate-holders, held at distances of live or six feet from the 



