Temperature on Modulus of Rigidity oj Solid Metals. 411 



decreases according to parabolic law. On the other hand,, 

 the logarithmic decrement decreases at first, reaches a 

 minimum at about 100° C, and then begins to increase. 



6. Nickel Fig. 10. 



Different from the foregoing metals, nickel is a ferro- 

 magnetic substance. In the ferro-magnetic region, that is 

 up to 400° C, the diminution of rigidity with the rise of 

 temperature is relatively small, but above that temperature 

 considerably rapid. From ordinary temperature to about 

 80° C. the logarithmic decrement decreases, and then in- 

 creases to reach a maximum at about 160° C. Afterwards 

 it slightly decreases to 250° C, and then increases very 

 rapidly. The result completely agrees with that obtained 

 by C. E. Ghiye and H. Schapper before referred to. The 

 existence of the maximum is due to the resultant of the 

 increasing effect due to temperature and the decreasing 

 effect of the magnetic transformation of nickel. 



7. Pure Iron. Fig. 11. 



The pure iron used in the present experiment was obtained 

 from the Bureau of Standards, Washington. It contains 

 only 0*0085 per cent, of carbon, other impurities amounting 

 in all to 0'01 per cent. 



From the room temperature upwards the rigidity of the 

 ferro-magnetic wire decreases at a slightly increasing rate,, 

 and even at 600° C. has still a large value. The logarithmic 

 decrement of pure iron decreases at first rapidly, reaches an 

 inconspicuous minimum, and then slowly increases. Above 

 300° 0. its increase is very rapid. The course of the curve is 

 the same as those obtained by Pisati, Tom] in son; and Horton 

 already referred to. 



8. Steels containing 0'55, 0*9, and 1*3 per cent, of Carbon. 

 Figs. 12, 13, & 14. 



We also measured the rigidity of three steels, representing 

 hypo-eutectic, eutectic, and hyper-eutectic steels respectively. 

 We see from the curves that the rigidity at ordinary tempera- 

 tures decreases with increasing- carbon. The course of the 

 rigidity-temperature curves is similar to that of pure iron, 

 with the exception of an abrupt fall in the vicinity of 200° 0.. 

 indicating the presence of the cementire transformation in 

 the steels. The logarithmic decrement-temperature curves 



