432 MR. J. E. H. GORDON ON MEASUREMENTS OF ELECTRICAL CONSTANTS. 
Best quality gutta percha. 
b 
■7 86 
•789 
•787 
•789 
> mean *788 
a, (2) 1-517 U515 1*515 
(1) 1-048 1-048 1-047 
a,—a l -469 -467 -468 
Mean "468. 
K=2-462. 
Chatterton’s compound. 
•842 "1 
6 ,| - 834 J 
j -826 0 
[_ "830 J 
a z 1-555 
a x 1-048 
«o—% -507 
"834*0 
!> mean -833 
•832 j 
1-555 1-555 
1-049 1-048 
"506 "507 
Mean "5066. 
K = 2-547. 
Sulphur. 
This plate was not a very good one, and was cracked across one corner.! 
4 745 ' 
[•mean -748. 
l -751. 
1 
a. 2 
1-496 
1-492 
1-507 
1-035 
1-037 
1-038 
a.^ — 
a x -461 
•455 
•469 
Mean "4583. 
K=2-58. 
* The four measures being taken at the four sides in order, the agreement of these two means shows 
that the slope is uniform. 
f It was prepared by casting in a mould with glass sides. It was semi-transparent for some hours 
after it had set, but became opaque before the experiments were made. 
