100 BE. JOULE ON SOME THEEMO-DYNAMIC PEOPEETIES OF SOLIDS. 
first method to obtain the absolute thermal effect gare 53', which was found to indicate 
a temperature of - 0°-162. The theoretical result in this case was 
.^5 
^"“ 1390^ 1 ^ 
1 * 
81633 ^-1024 '^•1499 
It 
X 
-=-0°-125. 
26. Cast Iron.— T\i& deflections produced by tensile forces of 194, 388, and lbs. 
were 1 7', 31', and 59'-9 respectively. The thermal effect indicated by the last was — 0°T605. 
The formula gives 
277-4. ”775 _ u _ 1§ 
H=- 
X 
1390 '^ 1 -^90139 ^-1198^ -1281 
27. In another experiment I obtained a thermal effect of — T481, theoiu giving 
-=-0°T12. 
H= 
283 1_ 1 
^ ’ '^ 90139 -1198 
X 
-=-0°-115. 
'1390'^ 1 '' 90139'' -1198'' -1281 
28. With tensile forces of 191-6, 383-3, and 766-6 lbs. I obtained by the 
first method deflections of 21', 41', and 1° 12'-6 respectively, the absolute thermal effect 
indicated by the last being ~0°-174. The formula gives 
111 _ 111 1 
274-9^^ ”766-6 
- "“ 1390 ^ 1 
v-r47rr=~0°-154. 
^ 58200^-095 ^ -1781 
29. With copper, and also vsdth iron wires, I have observed the cooling effect of tension 
close up to the breaking-point. But whenever the puU occasioned permanent change of 
figure, the heat frictionally evolved overpowered the cooling effect. 
30. Lead. The bar employed was half an inch in diameter, and weighed 6308 grains 
to the foot. The stretching weights were, first, 193 lbs. with 70 lbs., the weight of the 
lever, constant ; and second, 263 lbs., the weight of the lever itself being used along with 
the 193 lbs. laid on it. Using the first method, I obtained with the above weights deflec- 
tions of 21'-5 and 30'-7, indicating thermal effects of — 0°-0531 and — 0°-0<o8. Tlie 
formula gives in the two cases. 
TT 278-5 ”193 
-‘^“”1390-^ 1 
1** 
35100^-0303^-901 
1 
X-^=-0°-0403, 
and 
X-t-xi = -0‘’-0550. 
-0303 ^ -901 
1390-^ 1 35100 
31. Gutta Percha.—The piece used was half an inch in diameter, and weighed 1 l 46 
grains per foot. The thermo-electric junction, formed of very thin copper and iron 
wires, was inserted in a slit made two-thirds through the substance of the gmtta perch?. 
The weights employed were, first, that of the lever alone amounting to 70 lbs. ; and 
second, the lever with the further addition of 80 lbs., making in all 150 lbs. As with 
the metals, cold was produced when the gutta percha was stretched, and the heat 
restored when the stretching weight was removed. With the first-named tensile ^ojce a 
mean deflection of 16'-4 was observed, and with the second a mean deflection of oO -2. 
* Smexton. t POTTES. f EoT. § M5 Self. 
11 Latoisiee and Laplace, H Duloxg and Petit. Latoisiee and Laplace. 
