842 
ME. ^Y. HOPKIXS’S EXPEEI^^IEXTAL EESEAECHE^i 
which could materially alfect the results of the experiments. The values of - are foimd 
hy substitution in the formula 
k t^—T , 
One foot is adopted as the linear unit. 
The blocks were cylindrical, the diameter of then’ bases being about 3 inches. 
The blocks of spermaceti and wax, which were solidified under compression, were 
formed by pouring the substances in a fiuid state into a cylindrical hole in a strong block 
of iron, and leaving them to cool and solidify under the required pressure, applied by means 
of a piston exactly fitting the cylindrical hole, and rendered by proper peiiectly 
fiuid-tight. The piston was acted on by a powerful lever. When these substances were 
compressed after solidification, cylindrical blocks of them were formed of the proper 
dimensions before the compressing force was applied to them. Blocks of chalk, clay. 
&c. were compressed in the same manner. 
30. Exi^eriments made for the purpose of determining the effect of pressure 
on the conductivity of various substances. 
Spermaceti. 
I. {a.) Spermaceti, solidified under a pressure^;, on the square inch. 
The two cylindrical blocks are denoted by I. and II. 
Mean values 
I. -=-088 
c 
II. -=-08. 
. r ^ = -086 ft. 
' 1^0 = 900 lbs. 
jT rA='086ft. 
1^ = 6500 lbs. 
O’ 
9n-3 
^ 2 ’ 
68°-2 
67° 
t^. 
66°-6 
q. 
67° 
r. 
45° 
k 
-=•086 
c 
k 
-=•075 
c 
{h.) Blocks interchanged. 
I. 
II. 
q. 
90°-5 
69°-3 
68°-6 
r. 
470 
k 
-=•09 
k 
-=•086 
c 
II. Two blocks of spermaceti, one (I.) solidified under pressure, the other (II.) com- 
