194 Prof. A. Gray, Mr. V. J. Blyth, and Mr. J. S. Dunlop. 



diminishing then more slowly. The initial and final values are in the 

 ratio of 73 to 44. 



Diagrams V(6), V(c), V(d) are the curves of subsidence at two tem- 

 peratures for the 12*7 Ib. vibrator, the 18'7 Ib. vibrator, and the 24'7 Ib. 

 vibrator respectively. It will be observed that the curves of sub- 

 sidence are nearly alike in the two sets V(6) and V(c), only a very 

 slight difference in the direction of faster subsidence with the heavier 

 vibrator being visible. The curves of subsidence at the higher tem- 

 perature with the 24 '7 Ib. vibrator show distinctly more rapid sub- 

 sidence at the lower temperature than in any of the other three cases. 



Diagram VI shows the curves of subsidence for soft iron. Curves (1) 

 and (2) were obtained with the 12*7 Ib. vibrator; the former curve 

 gives the subsidence at the lower temperature, the latter at the higher 

 temperature stated in the diagram. It will be observed that the rate 

 of subsidence at the higher temperature is very much greater than at 

 the lower. These two sets of experiments were made in direct suc- 

 cession to one another on May 15. 



Next, on May 16, two sets of experiments at temperatures 15 0- 6 and 

 93 0> 8 C. were made with the 18-7 Ib. vibrator. The results of these 

 are shown in curves (3) and (4). Between these curves there is a 

 much smaller difference than between (1) and (2), though the tempera- 

 tures were very nearly the same. 



The high-temperature experiments were repeated on both days with 

 reproduction of practically the same curve. 



After twenty-four hours nearly had elapsed the experiments at the 

 lower temperature were repeated with the same vibrator, when the rate 

 of subsidence was found to be much slower at 13 '5 C. than it had 

 been on the previous day at 15 P 6 C. 



On May 18 two curves (5) and (6) were obtained with the 24*7 Ib. 

 vibrator at the respective temperatures 16 C. and 95'l C. Curve 

 (6) does not differ very widely from the curve (4) obtained on May 16 

 with the 18-7 Ib. vibrator; but the curve at the lower temperature 

 lies much to the right of that (3) obtained on May 16 at the lower 

 temperature, the companion curve of (4). 



All the results in curves (3) (6) show rates of subsidence lying 

 between those shown in (1) and (2). Curve (1) is approximately 

 exponential. It will be observed also that curves (2) and (4) show 

 the eomewhat rapid change of direction when the amplitudes have 

 become small to which attention is directed above in connection 

 with commercial copper. Curve (6), however, obtained at 95'1 C. 

 with the 24'7 Ib. vibrator, shows no such change of direction ; but a 

 considerable part of its curve, after the amplitude has been reduced 

 to about 10 C., is approximately exponential in character. All the 

 curves except (1) and (4'), however, show very marked diminution of 

 rate of subsidence at the lower amplitudes. It seems certain that 



