468 



ME. E. D. OLDHAM ON THE CONSTITUTION [Aug*. I906, 



phase ; and, if these be excluded, the interval will be a little longer, 

 and the apparent rate of propagation a little less, than is indicated 

 in the table. 



At 150° from the origin we find a remarkable decrease in the 

 mean apparent rate of propagation, which drops from an average 

 of over 6 to about 4| kilometres per second, and the most 

 obvious explanation of the decrease is that these waves, pene- 

 trating to greater depths, have entered, and for part of their 



Kg. 2, 



way traversed, a central core, composed of matter which transmits 

 them at a much slower speed than that traversed by the waves 

 emerging at lesser distances from the origin. The only other 

 alternative is that the time-interval is wrong, and that we are not 

 dealing with the second-phase waves at all. 



As regards this hypothesis, I may point out that all the deter- 

 minations used at distances of over 120° are derived from my own 

 examination of the original records or copies from them. In every 



