322 
PROFESSOR W. &. ADAMS AND MR. R. E. DAY ON THE 
No. 12 is a plate made up like Nos. 7, 8, & 10. It was annealed in hot sand. Its 
resistance at ordinary temperatures when measured with a battery of 20 Leclanche’s 
cells is about ’375 of a megohm. 
No. 14 is a piece similar to No. 11. Its resistance at ordinary temperatures is about 
•390 of a megohm. 
No. 15 is a piece very similar to No. 14, but it has evidently undergone the annealing 
process much better than No. 14, as its resistance at ordinary temperatures is about 
•025 of a megohm. 
No. 20 is a small piece of selenium stick, about 2 centims. long, made up like No. 11. 
It was annealed in hot sand, and its resistance at 14° C. is about 905 ohms. 
No. 21 is a piece of the same wire, made of the same stick, and annealed with No. 20. 
That it did not take the annealing so effectually is clear from the fact that its resistance 
at 14° C. is about 120,000 ohms. 
No. 22 was made up at the same time and in the same way as Nos. 20 & 21. The 
annealing was more successful than in the case of No. 21, its resistance at 14° C. being 
about 570 ohms. 
No. 23 is a small piece of a selenium stick about 4 millims. long, fitted up like No. 11. 
It was annealed in hot sand, and its resistance at 14° C. is about 58 ohms. 
No. 24 is a piece of the same wire, made up at the same time and in the same way 
as No. 23. Its resistance at 14° C. is about 55 ohms. 
No. 25 is a piece just like Nos. 23 & 24. Its resistance at 14° C. is about 68 ohms. 
The values of the resistances of the several pieces here given must only be taken as 
approximate ones, and are merely intended to show the general character of the resist- 
ance of each specimen. The resistance of any particular bar of selenium is so constantly 
altering, owing to the action of any currents that may be sent through it, that measure- 
ments of the resistance of the same piece, at the same temperature and with the same 
battery-power, made on two consecutive days, will hardly ever be found to give exactly 
the same results. As an example of this we will give the following Table of the resist- 
ances of most of the selenium plates mentioned in this paper, and which was compiled 
from observations made on the 8th and 9th of May. The battery -power was in all cases 
2 Leclanche’s cells, and the positive pole of the battery was always connected with the 
marked electrode of the tube. 
