350 THE ORIGIN OF THE OCEANS. [Aug. I907, 



Figures enclosed in parentheses represent times which are re- 

 garded as doubtful and have, therefore, not been used. 



The data from Strassburg and Laibach have been included, 

 although I have not been able to see either originals or copies of the 

 seismograms, as these observatories are equipped with a number of 

 instruments of different types, serving as a check on each other 

 and preventing the mistakes which may easily arise in the inter- 

 pretation of isolated records. In every other case I have examined 

 either the original or a copy of the seismogram. 



Discussion. 



The Chairman (Dr. A. Strahan) expressed his regret at the 

 absence of the Author. 



Prof. Sollas commented on the value of the evidence presented 

 by the Author, particularly as bearing on the internal consti- 

 tution of the earth. The facts suggested an increase of density 

 beneath the ocean-basins, and this was in accordance with what 

 recent speculations on the form of the earth might lead us to 

 -expect, especially in the case of the Pacific. Por complete con- 

 firmation of the Author's conclusions, however, numerous additional 

 observations were required. 



Postscript to the Discussion. 



[With reference to Prof. Sollas's remarks, the Author, who was 

 unable to be present at the reading of his paper, wishes to point 

 out that, while an increase of density would account for an increase 

 in the interval between the arrival of the first- and second-phase 

 waves, it would do so by a lessening of the rate of propagation, 

 of which there is no evidence, of the first- phase, as well as the 

 second-phase, waves ; apart from a difference in composition, the 

 most probable explanation seems to be an increased temperature 

 under the oceans. He is in perfect agreement with Prof. Sollas as 

 to the necessity for further observations; but, in the meanwhile, 

 he regards those referred to in his paper as having transferred 

 the burden of proof to the hypotheses which treat the ocean-basins 

 as mere irregularities of outward form of the earth. — B. D. 0., 

 July 20th, 1907.'] 



