Vol. 62.] CONSTITUTION OF THE INTERIOR OF THE EARTH. 475 



those instruments giving the greater amount of amplification of the 

 record. In the third phase, the record was principally due to tilting, 

 added to the natural swing of the pendulum, arid the displacement 

 due to these causes being much greater in the case of horizontal 

 pendula of comparatively -long period, the record was naturally 

 larger, despite the lesser degree of magnification. In practice 

 there was usually no difficulty in allowing for the differing 

 behaviour of different types of instrument, and in recognizing the 

 phases of the disturbance despite their great apparent contrasts 

 in appearance. As regarded the interpretation of the record and 

 the types of wave-motion, he believed that the one adopted by him 

 was most in accordance with all the facts; but he was ready to 

 adopt the Rev. 0. Fisher's alternative explanation of the second- 

 phase waves. So far as the conclusions drawn in his paper went, 

 the on]y essential point was that both these phases are due 

 to mass-waves of two distinct kinds, both propagated 

 through the earth, and not along or parallel to its surface. 



