314 
Proceedings of the Royal Society 
Effect on applying Pressure. 
Effect on relieving Pressure. 
Change of 
Pressure. 
Deflection 
Positive. 
Change of 
Pressure. 
Deflection 
Negative. 
48 
2 "9 
45 
2*7 
47 
2*8 
44 
2*6 
44 
2*6 
41 
2*5 
41 
2*5 
37 
2*2 
44 
2*7 
41 
2*5 
47 
2*7 
43 
2*5 
43 
2*5 
39 
2*3 
45 
2*6 
41 
2*5 
48 
2*8 
43 
2*6 
45-2 
2*68 
41*6 
2*5 
Thus taking the mean of nine experiments, and having found, in 
the manner referred to above, that 4*8 divisions on the galvanometer 
scale are equivalent to 1° C., we deduce the rise of temperature on 
applying tons on the square inch, to be 0°*56 C., and the fall on 
relieving tons to be 0°*52 C. Hence we can deduce the rise or 
fall per ton, as shown in the table under Vulcanite. 
Cork . — A parallelepiped, two centimetres long and one square 
centimetre in section, was cut from a piece as homogeneous as 
could be obtained. A reference to the following table will show 
that, for this substance, the fall of temperature on relieving pressure 
is considerably less than the rise on application of pressure. This 
result had been given by Professor Tait in a Hote in the Pro- 
ceedings (May 16, 1881), and it was to some extent with a view to 
the discovery of like anomalies that the present investigation was 
undertaken. But no other of the substances which we have tested 
showed this peculiarity. Each of the following results is the mean 
of six experiments : — 
Temp. 
in 
Degrees 
Centi- 
grade. 
Thermal Effect on applying 
Pressure. 
Thermal Effect on relieving Pressure. 
Pressure. 
Deflec- 
tion. 
Temp. 
Raised. 
Rise 
per Ton. 
Pressure. 
Deflec- 
tion. 
Temp. 
Lowered. 
Pall 
per Ton. 
15° 
22*3 
3*6 
0°*75 
0°*75 
23*2 
2*5 
0°*53 
0° *51 
15° *3 
45*2 
6*2 
1°*3 
0°*65 
44*5 
4*3 
0°*9 
0°*45 
15° *6 
65*6 • 
8*2 
1°*71 
0°*59 
59*5 
. 
I 
1°*12 
0°*42 
