180 APPLIED MECHANICS 
results, and the results on the bars as received, are shown plotted in 
Fig. 254. 
The maximum stress is in tons per square inch of the original area of 
the test pieces, and the elongation is the percentage elongation on a 
length of 2 inches in each case. The reduced parallel part of each 
specimen was ;3, inch in diameter before testing. 
; 50 
70° Maximum stresses shown by full lines’. 1 et es 
Elongations shown by dotted lines. ue ag 
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Carbon per cent. 
The full lines A, B, C, D, and E show the maxvmum stresses. 
The dotted lines a, b, c, d, and e show the elongations. 
A, a, refer to the bars as received from the rolls. 
B, }, refer to bars annealed at 900° C. for half-an-hour. 
C, ¢, refer to bars soaked at 720° O. for twelve hours, 
D, d, refer to bars quenched at 800° C. in water at 20° C. 
E, e, refer to bars quenched at 720° C. in oil at 80° C. and subsequently 
reheated to 350° C. 
Fig. 254. 
Bars as received.—The maximum stress for the bars as received from 
the rolls is about normal, but the elongation is extremely low. The low 
elongation was found, after microscopic examination, to be due, to a 
certain extent, to rapid cooling near a certain critical temperature. 
Annealing.—The test pieces were annealed as follows. “The bars 
were packed in lime in 3-inch wrought-iron tubes, closed at each end by 
screwed iron caps. These tubes were then packed in a large wrought- 
iron tube, the ends of which were covered by wrought-iron plates. This 
was placed in a closed gas-mufile, and a record of the temperature was 
taken by means of two thermo-couples attached to an autographic 
recorder.” After attaining the temperature desired, the contents of the 
