AND STRAIN ON THE ACTION OF PHYSICAL FORCES. 
59 
X and Y are the two wires to be compared, the clamp A rests as before on the top 
of the air chamber, and of the two clamps B B fastened to the lower ends of X and 
Y one has a stout iron wire attached to it for the purpose of a suspension for the scale- 
pan. Also to each of the clamps B are soldered two silk-covered copper wires -^th of 
an inch in diameter and 3 feet in length, one of these serving to connect the clamp 
with one of the battery wires and the other with the caoutchouc-covered wire leading 
to the resistance coils. The wires X and Y were each 3-| feet in length, but were not 
cut off from the 8 feet pieces, the remainder of the wire* being allowed to hang down 
on the outside of the air chamber, whilst the silk-covered copper wires fastened to the 
clamps B B were brought down through the hole in the table at the bottom of the 
air-chamber. When the experiments on the hard-drawn wire had been finished, the 
metal was well annealed and similar ones made on it in this new state, with this 
difference, however—that now the wire X was tested with larger and larger loads until 
it finally broke. The results of the experiments made on the wire in the hard drawn 
and annealed conditions will be found in Table IV. 
The curves in Table V., showing the temporary alteration of resistance produced in 
the annealed wire by different loads after the wire had been previously stretched for 
some time with weights of 16, 18, 20, 22, and 24 kilogs., are drawn with their 
abscissae to represent the percentage alteration of resistance on a scale of ’0025 to the 
millimetre, and with their ordinates the number of kilogrammes per square centimetre 
in the load on a scale of 25 kilogs. to the millimetre. 
Table IY. 
Condition. 
Section in 
square centims. 
Specific gravity 
at 20° C., 
water at 4° C. 
= 1 . 
Specific resistance 
at 20° C. 
Torsional rigidity 
in grms. per 
square centim. = r. 
“ Y oung's modulus ” 
in grms. per 
square centim. =e. 
Ratio 
of lateral 
contraction to | 
elongation. 
Hard drawn 
Annealed 
•005832 
•005832 
87066 
87386 
1757XlO- 8 
1736x 10-8 
723-5 x 10 6 
758-5 x 10 6 
2270-6 X 10 6 
2174-6 xlO 6 
•570 
■433 
Not shown in the figure. 
