Intelligence and Miscellaneous Articles. 79 



cylinder, 4 centim. in height and 2 centim. in diameter, .was sup- 

 ported on a rod of shellac, and had a lid which could be lifted off by 

 means of an insulating rod of shellac. A third rod of shellac was 

 fixed to the under surface of the lid, and in it was fused a thin brass 

 wire which was wrapped round the tourmaline. 



The tourmaline used was of a green colour, very transparent, 

 fractured on both sides, and for a length of 2 # 05 centim. weighed 

 1*59 grm. 



One pair of quadrants of the electrometer was put to earth. A 

 volt was represented by a deflection of about 2-5 centim. on the 

 scale, at a distance of 130 centim., which was sufficient for the 

 present purpose. It was more important that the insulation of 

 the one pair of quadrants should be good, and that it should not 

 receive a charge from the movable part of the electrometer, or 

 from the air in the room, than that the electrometer should be very 

 sensitive. These conditions were more than sufficiently satisfied. 

 For when electricity was imparted to the insulated pair of quadrants, 

 the deflection only sank in forty minutes from 14-0 to 13-3 ; and, 

 further, after insulation for three quarters of an hour without charge, 

 there was a deflection of 0*4 centim. 



The shellac rod which supported the cylinder also insulated well ; 

 for after being connected with the insulated pair of quadrants, the 

 deflection sank in eleven minutes from 32-2 to 304. 



The capacity of the insulated pair of quadrants was found in 

 several experiments to be about seven times as great as that of the 

 cylinder. 



In the experiments the second pair of quadrants, from which a 

 wire passed to the cylinder, was connected with that to earth. 



The lid with the crystal was raised, the latter heated in one end 

 of the flame of a Bunsen burner or spirit-lamp, again brought into 

 its place, and the connection with the two pairs of quadrants 

 rapidly broken. 



However the heating ivas arranged, no deflection was ever obtained 

 which exceeded the uncertainty of the instrument, although the quan- 

 tities of electricity developed were often considerable, and were fre- 

 quently of the same hind at both ends. 



Erom a long series of experiments I select the following. 



When the crystal was heated at one end, and after a minute 

 removed from the cylinder, the proof plane applied to the crystal 

 and then to the insulated pair of quadrants showed negative elec- 

 tricity at both ends, the deflections at the top and bottom being 

 3*0 and 7*50 centim. respectively. 



In another case there was no apparent electricity at one end, 

 while that of the lower sent the image out of the field. 



If the duration of heating was somewhat greater, and the crystal 

 remained longer in the cylinder, there was on the top positive, and 

 on the bottom negative, and of such strength that often, on raising 

 the lid with the crystal, the luminous image disappeared from the 

 scale, which is simply explained by the fact that part of the 

 electricity induced on the cylinder is removed with the lid. — 

 Wiedemann's Annalen, November 10, 1885. 



