On the Induction Apparatus and its Effects. 



119 



or of the laws of isomorphism ; and many minerals might then 

 have been considered true and distinct species which would be 

 now united. The following Table of old analyses of tourmaline, 

 given in Dr. Thomson's original book, will at once show how 

 highly probable it is that zeuocite is in reality nothmg but tour- 

 maline, and that at that time no better analysis could have been 

 expected. 



Not only does the specific gravity of zeuocite agree with that 

 of tourmaline, but its behaviour before the blowpipe, as described 

 by Dr. Thomson, is also similar ; and it is worthy of remark, he 

 mentions that the water in zeuocite contained traces of muriatic 

 acid. Had he tried for boracic acid, he would more probably 

 have found it was boracic acid. 



XVII. On the Induction Apparatus and its Effects. 



By J. C. POGGENDORFF. 

 [Continued from p. 12.] 

 2. On the Phenomena observable during the Action of the 

 Apparatus. 



HITHERTO it has not at all, or has not sufficiently been 

 kept in view, that the phcenomeua manifested by tiie ap- 

 paratus are essentially different according as the ends or poles of 

 the induction wire are either (1) connected by means of a good 

 conductor, or (2) separated by air or gas, or (3) separated by 



