EFFECT OF TEMPERATURE ON COPPER. 291 
considerably in different 
specimens or at least in the 
particular set of specimens 
under discussion. 
9. Temperature and per- 
manent compressions.— Six 
tests were made, and the 
corresponding autographic 
diagrams obtained, on cylin- 
ders of the dimensions stated 
below, in order to determine 
the effect which a change in 
the temperature has upon 
the permanent compression 
produced by any particular 
stress. The autographic dia- 
grams are reproduced in 
Fig. 8. 
=Compressior 
$ ‘250: 823.7. 
oo) 
Fig. 8. 
Table IIL. 
| Wo. of Original | Maximum Load. Final Total Temperature] 
| Test.| Length.; Diam. | Area. | Total. Per sq. in. Length. |Compression.| of Test.» } 
—_———} i ates pte oe 
| 45 | 1555; -997 |-7807 | 35000 | 44830 957 “198 62 | 
| 46 | 1160} -997 |-7807 | 35000 | 44830 ‘946 ‘214 123 | 
| 47 | 1:185| -997 |-7807 | 35000 | 44830 943 242 199 | 
| 48 | 1-166| -997 |-7807 | 35000" | 44830 | ‘804 | ‘272 300 | 
49 | 1:162| -997 |-7807 | 35000 | 44830 ‘849 | °313 396 | 
50 | 1:160| -997 | -7807 | 35000 | 44830 ‘823 | °337 404 | 
Test No. 45 was made in air. 
It is evident that the copper is rendered much more plastic by 
the increase of temperature. The ‘yield point,’ or point of marked 
departure of the autographic diagram from the vertical is lowered 
