Explosive Efect of Electrical Discharges. 283 



terminals, exhibited, on development, brush-discharges or 

 Lichtenberg figures. 



The measurements were next repeated, while at the same 

 time spark-discharges were measured in a transformer circuit, 

 the primary of which was in the circuit of the high-tension 

 transformer or Plante machine. In the following table 

 column A contains the length of spark in the primary circuit, 

 or circuit of the Plante machine ; column B the length of 

 spark in the secondary coil circuit. 



A. 



B. 



A. 



B- 







2o 



16 



2-8 



1 



2-7 



20 



26 



2 



3-0 



30 



1-7 



3 



30 



40 



1-8 



4 



30 



50 



1-6 



5 



30 



60 



1-3 



6 



32 



70 



1-2 



7 



33 



80 



10 



14 



3-0 



1 





When these results are plotted the resulting curve B (fig. 2) 

 shows that the spark-length in the secondary circuit increases 

 while the primary spark-length is increased up to 7 centim. 

 When, however, the primary spark-length is increased to 

 14 centim., the length of the secondary spark begins to 

 diminish. Thus the maximum of the lower curve B is a 

 little in advance of the minimum of the curve representing 

 the explosive action. Since the magnetic flux through the 

 little transformer is proportional to the strength of the current 

 in the primary circuit, it is seen that the explosive effect is 

 not due to the heat produced by the current. Previous expe- 

 riments by one of us * had shown that the apparent resistance 

 of the primary spark did not increase with the length of the 

 spark. The diminution in the magnetic flux is not due to 

 increase of resistance in the primary circuit, but toashuntino- 

 through the air of the current in this circuit. Fig. 1 shows 

 how great this shunting action can be, even with closed circuits 

 under the action of high electromotive force. 



The explosive effect, therefore, we are inclined to attribute 

 primarily to an electrostatic action. When the primary spark- 



* Proc. American Academy of Arts and Sciences, vol. xxxiii. No. 24. 



