Notices, res-peeling New Boohs. 145 



Another experiment was to connect one lamp terminal by a 

 wire to the coil, connect the other lamp terminal to earth, and 

 short-circuit the lamp through the body by grasping the coil 

 terminal with one hand and a piece of metal connected to 

 earth with the other. The effect of so doing was to reduce 

 the incandescence of the filament to rather less than one half 

 its normal amount, half of the available current going appa- 

 rently through the lamp, the other half through the body. 



With the lamp terminal connected to the coil, it was found 

 unnecessary to connect the other lamp terminal to earth to 

 produce incandescence, all that was necessary being to touch 

 this lamp terminal with a piece of metal held in the hand. 

 That the incandescence of the filament produced under these 

 conditions was due to the electrostatic capacity of the operator 

 and not to his forming a connexion to earth, was evidenced 

 by the fact that it made no perceptible difference whether he 

 stood on the floor or on an insulated stool. 



In all the above experiments the second terminal of the oil- 

 coil was free and not connected to anything. It was, how- 

 ever, found that the effect of a second operator touching this 

 terminal, or of connecting it by wire to earth, was to diminish 

 the incandescence of the lamp-filament. It was also found 

 that the filament incandesced to a greater degree of brightness 

 when connected as above between one terminal of the coil and 

 earth, than when it was directly connected between the two 

 terminals of the coil, but that, while the operator experienced 

 practically no sensation when his body was inserted between 

 one terminal and earth, the sensation was very severe — in fact, 

 quite unbearable — when the body was inserted between the 

 two terminals. The above seem to show that capacity has 

 much to do with the results obtained, and that the phy- 

 siological effects of electric currents are not necessarily 

 proportional to their heating-power. 



It should also be mentioned that in some of the experiments 

 there was a decided tendency for the filament to vibrate in 

 unison with the contact-breaker of the induction-coil. In 

 fact, in some cases the amplitude of vibration was sufficient to 

 cause the end of the filament to beat against the glass of the 

 lamp bulb. 



XVIII. Notices respecting New Books. 

 Annals of British Geology, 1891. By J. P. Blake, 31. A., F.G.S. 



8vo. Pages viii & 404. Dulau and Co., London, 1892. 



TN a review of the former volume (for 1890) in the Philosophical 



■*• Magazine for March 1892, the plan of these "Annals " was fully 



described. It has been followed in the present volume, except 



Phil. Mag. S. 5. Vol. 35. No. 213. Feb. 1893. L 



