58 A. G. Bell— Exploring for an imbedded bullet 
makes contact with the surface of the bullet C, a galvanic 
battery will be formed naturally within the body, the two poles 
of which are respectively the Jeaden bullet C and the metallic 
plate B. Under these circumstances a click will be heard from 
the telephone each time the bullet is touched by the needle. 
This has been verified by experiments upon bullets buried in a 
Further modifications of Induction Balance.—I sailed for Hurope 
early in October, 1881, and have had no opportunity since of 
continuing my researches until quite recently. While I was in 
Europe, however, Mr. Sumner Tainter devised a new kind of 
induction balance which deserves mention here. The results 
obtained with this apparatus in its present form (fig. 29) are 
not to be compared with those produced by the best instruments 
described above, but there are undoubtedly great possibilities 
of future development. — ; 
rheostat R. Coils A and © are exactly similar; and if the 
resistance introduced at R is equal to the resistance of the ex- 
ploring coil KE, an acoustic balance can be obtained by the ad- 
Justinent of the secondary coils B D upon the primaries A O; 
but if the resistance introduced at R is different from that at 
E, Mr. Tainter states that no balance is possible. 
en the apparatus is adjusted to silence the approach of 
a bullet to the coi] E destroys the balance. 
