1869.] 



with the Great Induction Coil. 



71 



10 cells. 



inches. 



1st section, nearest core 8^-, wiry spark. 



2nd „ 8f, „ „ 



3rd 8, bright blue wiry spark. 



4th ,, 9f, slightly flaming. 



15 cells. 



inches. 



1st section, nearest core 10, slightly flaming. 



2nd „ 101, „ 



Srrl 



*»J u jj a }> 



4th „ llf, flaming spark. 



20 cells. 



inches. 



1st section, nearest core 11^-, flaming spark. 



2nd „ ...12, „ 



3rd „ 11, „ „ 



4th „ 12£, „ 



If the two wires from the secondary coil are placed in water, no spark 

 is perceptible, even when they are brought very close together, until they 

 touch. 



If the negative wire is passed through a cork, on which a glass tube (a 

 lamp-glass) is fixed containing a depth of 5 inches of water, and the 

 positive wire is brought within half an inch of the surface of the water in 

 the tube, it becomes red-hot ; and if drawn further away from the surface, 

 the upper part of the tube is filled with a peculiar glow or light abounding 

 in Stokes's rays. 



The experiments with the vacuum-tubes, and especially Gassiot's cascade, 

 are, as might be expected, very beautiful. When a coal-gas vacuum-tube 

 of considerable diameter, and conveying the full discharge from the se- 

 condary coil, is supported over a powerful electromagnet axially, the 

 discharge is condensed and heat is produced. 



If placed equatorially, the heat increases greatly ; the discharge is con- 

 densed and impinges upon the sides of the glass tube, which becomes too 

 hot to touch ; and if the experiment had been continued too long, no doubt 

 the tube would have cracked. 



The enormous quantity of electricity of high tension which the coil 

 evolves when connected with a battery of 40 cells, is shown by the rapidity 

 with which it will charge a Leyden battery. 



Under favourable circumstances, three contacts with the mercurial break 

 will charge 40 square feet of glass. 



