94 
MR. H. TOMLINSON ON THE INFLUENCE OF STRESS 
Table XIII. 
Metal. 
Percentage 
value of 
the equal 
increments 
of 
resistance. 
•0314 
•0311 
•0305 
•0298 
•2270 
•9620 
T524 
T487 
T482 
•0609 
•0601 
•0582 
•0552 
load 
Actual 
on the 
wire in 
kilogs. per 
square 
centim.=p. 
Ratio of 
consecutive 
time 
calculated 
for an 
increase of 
*1 per cent, 
of 
resistance 
—r. 
Calculated 
breaking-load 
r — 1 
+ - : - 
r x •000501. 
1448 
1570 
1759 
1971 
3811 
1418 
1737 
1836 
1946 
1076 
1192 
1440 
864 
2'5/'2 
2-097 
1-721 
1-492 
1-081 
1-014 
1-131 
1-064 
1- 029 
2- 531 
2-015 
1-498 
1T44 
2666 
2612 
2593 
2628 
3826 
1446 
1968 
1956 
2004 
2281 
2195 
2099 
1295 
Observed 
breaking¬ 
load in 
kilogs. per 
square 
centim. 
2625 
3816 
3785 
3867 
1468 
1528 
1426 
2061 
2080 
2099 
2090 
2272 
2170 
1277 
1304 
1288 
Mean 
values of 
breaking¬ 
loads from 
observation 
and 
calculation. 
2625 
3825 
1460 
2021 
2185 
1293 
Ratio of 
“ Young's 
modulus'” to 
breaking-load. 
4-35 x 10 2 
5-17 „ 
5-25 „ 
7-20 „ 
3-44 „ 
5-19 „ 
Mean 5'10 X 10- 
Observations on Table XIII. 
We learn from the above table how very closely in all cases the calculated breaking¬ 
load agrees with the observed breaking-load, though the values of p and of the per¬ 
centages of increase of resistance for which the times were observed varied considerably. 
What differences do exist are no greater than those between the values of the observed 
breaking load for different pieces of the same wire. 
Since, also, the permanent increase of resistance produced when a wire is running 
down under the influence of a load is for small amounts nearly double the increase of 
length, we may determine the breaking load by observing the times taken by the load 
to produce successive equal increments of length amounting to -05 per cent., and use 
the same formula as above.'"' 
In estimating the breaking-load as has been before mentioned, the diameter of the 
wire was gauged in the immediate neighbourhood of the breaking-point; and this is 
necessary if we wish to determine the true breaking-load in kilogrammes per square 
centimetre, inasmuch as, however uniform in diameter, and however carefully annealed 
* It should be noticed that the value of r as used in the formula is 'greater than unity, and is obtained 
by dividing the succeeding by the preceding time of accomplishing any two consecutive increments of 
resistance or of length. 
