390 



RECENT PROGRESS IN PHYSICS. 



The divergence 24.6 and 8.87 correspond to the quantities of elec- 

 tricity, G ana 1 G, which likewise are very nearly in the proportion of 

 4 to 1 ; thus again at a double distance, we have one-fourth the quan- 

 tity of latent electricity. 



I should think that these experiments were sufficient to place beyond 

 doubt, the principle that, the quantity of electricity loMcli is rendered 

 latent on an uninsulated conductor by a neiglihoring insidated electrified 

 body, is in the inverse proportion of the square of the distance of fhetioo 

 bodies, provided that their dimension and the distance, are such that 

 the electrical force can be considered as concentrated in their centres 

 of gravity, without considerable error. 



In the experiments of Knochenhauer , the distance between the in- 

 ducing body and that upon which the opposite electricity^ is rendered 

 latent, was much less than in mine ; his least distance was 3 lines, 

 mine was 3 inches. This fact gives rise to the supposition that in his 

 experiments, electricity may have gone over. To find out whether 

 this could really have happened, I made the distance 

 between the ball a and the electrometer plate, 3 lines 

 in the clear, and then placed the electrometer so that 

 the distance of the plate from the centre of the ball 

 was double as great as in the first position. In this 

 case also at a double distance, the effect was about 

 one-fourth, consequently, no electricity had passed 

 from the ball to the plate. 



But the ball was quite large, and the plate, a por- 

 tion of an indefinitely large sphere ; the ball a, more- 

 over, was varnished ; circumstances far less favorable 

 to the passage of electricity than in the arrangement 

 of Knochenhauer. 



I now exchanged the ball a for another not var- 

 nished, and only 8 lines in diameter ; the plate of 

 the electrometer was removed and replaced by a ball 

 about 4 lines in diameter. When the distance be- 

 tween the balls amounted to 12 lines or 18 lines be- 

 tween their centres ; on repeating the experiment in the above de- 

 scribed manner, I obtained from a charge, which of course had to be 

 quite weak, a divergence of 8 to 10 degrees; but when the electro- 

 meter was brought so near, that the distance in the clear amounted to 

 only 3 lines, the distance of the center being then only half as great 

 as in the first position, for equal charges of the small ball a, there was 

 not a divergence of the pendulum anything near four times as great 

 as before, but a divergence of only 10°. 



Evidently electricity had gone over between the balls, hence the 

 charge of the upper ball, as well as the quantity of latent electricity 

 on the lower one, was considerably diminished. 



There is not the least doubt, that tliis acted injuriously in the exper- 

 iments oi Knochenhauer, and made his results perfectly valueless. 



[ § 20 is oiriitled for reasons mentioned under § 18] 



§ 21. Faraday's researches on latent Electricity. — Faraday also 

 has made the induction of electricity a subject of research. In his 



