300 Prof. A. Gray and Mr. A. Wood. Effect of a [May 1, 



Diagram III brings out the point just alluded to more clearly. 

 These curves show the effect of the different fields upon the amount of 

 subsidence effected in the times corresponding to different numbers of 

 vibrations and to different amplitudes. For example, Curve 1 gives a 

 comparison of the subsidences (from an initial amplitude of 90°) 

 effected in twenty vibrations under different fields varying from about 

 100 to 200 C.G.S. Curve 2 gives a comparison of the subsidences 

 from the same initial amplitudes effected in thirty vibrations for the 

 same range of field. Curves 3 and 4 show the subsidences for forty- 

 five and seventy -five vibrations respectively in the same circumstances. 

 It will be seen that the points of maximum of the curves trend to 

 the right from Curve 1 to Curve 4 — that is to say, the value of the 

 field which produces maximum effect is greater the smaller the 

 amplitude of the vibration to which it is applied. 



Remits for Iron. — Diagram IV shows curves of subsidence obtained 

 for iron. Six curves are given showing the results for fields varying 



54> 



63' 



J 



16 



£4 



AmpUbude. 



7B Q 



er 



90" 



Diagram IV. 



Field. 

 C.G.S. 

 22 ., 

 44 „ 



Curve. 

 4 



5 

 6 



Field. 

 81 O.Gr.S. 

 170 „ 

 229 „ 



from to 230 C.G.S. It will be seen that the curves fall successively 

 to the right of one another with the exception of 5 and 6, which are 

 practically coincident. Experiments were also made for fields up to 



