﻿Mr. Rollo Appleyard on Dielectrics. 

 Table IX. 



407 



No. of Kod. 



Proportion 



by weight 



G.P. 



Brass' 



Approximate Resistance. 



1 



2 



3 



4 



5 



6 



7 



8 



9 



10 



11 



12 



13 



14 



15 



i 



2 

 ? 



i 



l 

 l 



1 

 l 



2 



3 



♦ 



1 

 2 



1 

 2 



3 



1 

 5 



1 

 2 



i 



1 1 



•2 ohm. 

 •07 „ 

 •11 „ 



00 . 

 00 . 



283,000 megohms. 

 173,000 



00 . 



770 megohms. 

 •37 ohm. 

 1-68 „ 

 19 ohms. 

 3-9 „ 



•48 ohm. 

 1*5 megohm. 



Table IX. gives the proportion by weight of these rods and 

 the corresponding resistance. When rods made up in this 

 way are submitted to the action of oscillating discharges, they 

 behave in a similar manner to the " impulsion w cells of Prof. 

 Minchin and the tubes of M. Branly. If, for instance, one 

 of the low-resistance rods of, say, four parts by weight of 

 gutta-percha to nine of brass filings is connected to one arm 

 of a Wheatstone's bridge and balanced, an oscillatory dis- 

 charge made anywhere near it will, in "early all cases, pro- 

 duce a considerable diminution of resistance — in some cases 

 amounting to more than 10 per cent., and, in one experiment, 

 to as much as 45 per cent. This charge remains until restored 

 to the former condition of things by a slight mechanical tap. 

 I have repeated this experiment upon seven different rods, 

 and have, in each case, obtained a diminution when the dis- 

 charge-spark passed at the oscillator. The small- resistance 



