86 Dr. J. Miiir. On Changes in Mastic Properties [Aug. 11 



calculating the reduced areas from the extensions obtained (omitting 

 the local extensions at points of fracture) and neglecting the small 

 changes in density which are known to be produced by stretching. 

 Copper thus resembles iron and steel in having its breaking stress 



! ipooLbs/in s . 



Diagram No. 5. — (Copper.) 



Extensions diminished bu J°°- of <5tn inch for everu\ 



00,000 3 ooo pounds of streM 



Scale :- 1 Unit=^ i L h of an inch 



Diameter of specimens 

 Specimen A. 



0"-37. 



4"-00. 



Length under test 



-Copper as supplied. Broke at 35,300 lbs. per square inch original 

 area, or after an actual stress of 41,600 lbs. per square inch had 

 been applied to the bar. Extension on 4 inches, //, 74 omitting, 

 or l r/, 04 including, local extension. 



Specimen B.— Heated to 630° C. and slowly cooled. Broke at 33,500 lbs. per 

 square inch original area, or 40,800 lbs. per square inch actual 

 stress. Extension on 4 inches, 0""87 omitting, or 1"'25 including, 

 local extension. 



Specimen C.— Quenched from 500°, 550°, and then from 600° C. Broke at 32,300 lbs. 



per square inch original area, or 44,200 lbs. per square inch 

 actual stress. Extension on 4 inches, L //- 50 omitting, or 1"'98 

 including, local extension. 



increased by quenching, but differs from iron and steel in giving a 

 greater extension before fracture when in the quenched condition. 

 The abrupt yield-point which is so striking a feature in the testing of 

 annealed iron and steel, is not exhibited with copper. The ultimate 

 extensions obtained with the three specimens of copper tested were 

 0""74 on 4 inches with A, 0"*87 with B, and l"-50 with C, omitting 



