246 PROFESSOR E. G. COKER ON 
The specimen failed by bending at the lower end, due no doubt to the compression 
plate being provided with a hemispherical seat. 
The galvanometer readings uncorrected (fig. 8) show a marked deviation from a_ 
straight line, but the corrected readings follow a linear law almost exactly, and show 
no trace of the bending stress, as the thermopile was set against the top of the 
specimen farthest from the place of failure. j 
The strain readings are plotted on the figure for comparison, and it is evident that 
the linear correspondence is quite definite. As a further example, the following test 
may be quoted of a steel specimen 1°01 x ‘38 inches in section and 43 inches in length, 
The value of & found by a preliminary test was ‘0089, and the test gave the followimg 
readings :— 
Tanne Vn. 
| 
Galvanometer 
; Extensometer Galvanometer Readings. 
Load, pounds. Time, seconds. | Reading. Readings, @onrccraal 
| Uncorrected. k= ‘0089. 
| i: 
1,000 0 0 | 0 0 
| = 57 
3,000 10 | 57 2°8 2°93 
| — 55d 
5,000 2) Wi 6:0 6°52 
— 56 
7,000 29°5 / 168 9°3 10°50 
— 53 
9,000 40 | 22) 11:5 13°50 
— 60 
11,000 n1 | 281 13°9 17:00 
. — 62 
13,000 60 343 166 21:00 
| — 60 
15,000 70 403 18°5 24°30 
| — 58 
17,000 81 461 20°1 27°30 
-65 | 
19,000 90 526 | 22°2 31:20 
100 Went off scale 23:5 34:00 
110 
Notes.—Long connecting leads. 
Distance of scale from galvanometer mirror = 10’ 2 
“ 
of the stress, showing that the stress had been carried nearly to the point of failure, 
but this is not apparent in the plot of fig. 9. 
Other compression tests showed the same general characteristics, and we may 
and steel is linearly related to the stress applied through approximately the same 
range as the strain. 
