CONTRIBUTIONS FROM THE JEFFERSON PHYSICAL LABORATORY, 

 HARVARD UNIVERSITY. 



ELECTRIC DISCHARGES. 

 By John Trowbridge. 



Presented October 11, 1905. Received January 11, 1906. 



I. Slow Moving Electrical Luminous Effects. 



Our knowledge of electrical manifestations is based upon the com- 

 paratively feeble effects which we can produce in laboratories ; and even 

 with the best appliances which modern applications of electricity afford 

 we are far within the limit of lightning discharges. 



It is unsafe, therefore, to assume that the testimony of many observ- 

 ers in regard to ball lightning and slow moving discharges, observed by 

 them in electric storms, has its origin in disordered nerves. The follow- 

 ing experiments lead me to believe that a slow ionization of rarefied air 

 might be caused by currents of electricity of great strength following 

 lanes of» such rarefied air in thunder-storms. 



The most notable experiments upon slow moving electrical luminous 

 effects are those of Rhigi. 1 He charged condensers of large capacity by 

 means of an electrical machine ; discharged them through a large liquid 

 resistance, and observed globular or elongated spindle-shaped discharges 

 which moved slowly along the tubes of rarefied gases. He gives reasons 

 for believing that such discharges are not striae, but that they belong to 

 a particular kind of discharge. 



It is to be noted that he interposed a spark gap in the discharge 

 circuit. 



I have repeated Rhigi's results, using instead of discharges from large 

 condensers the current from a storage battery of 10,000 cells without 

 the interposition of a spark gap, and I obtain slow moving luminous 

 effects such as are represented in the illustrations of his memoir. These 



1 Nuove Esperienze sulle Scintille Electriche, Constituite Da Masse Lurainose 

 che si Muovono Lentamente. R. Accademia, delle Scienze dell Instituo di Bologna, 

 19 Maggio, 1895. 



