AND VALrARAlSO EAKTHQUAKES AND THEIR CAUSES. 57 



I should like to ask Professor Hull what, in his view, is the general 

 <3xplanation of the circumstance that earthquake waves which are 

 propagated through loose geological formations are more disastrous 

 than those propagated through firm ones as stated by the author. 



We shall concur with the learned author that these destructive 

 visitations afford no argument against the goodness of God and 

 His over-ruling power ; and that it is death itself, not its method or 

 mode, that claims our serious concern. Undoubtedly, the only sure 

 basis for a rational fortitude in presence of death is that unlimited 

 trust in God which was possessed by Job. 



Professor Logan Lobley, F.G.S. — Besides being an interesting 

 account, Dr. "Warren Upham's paper contains some points of 

 considerable scientific and seismic value. AVith its main contention 

 that the two earthquakes were of tectonic and not of volcanic 

 origin I am in entire agreement. 



Such earthquakes are the result of forces originating j^ressures, 

 strains and tensions which, when resistance is overcome produce, a 

 ^sudden movement of the surface rocks. The whole of the Pacific 

 •coast of America is being elevated, and it is this that causes its 

 frecpient and sometimes disastrous earthquakes, as well as the 

 volcanic activity which is also a conspicuous characteristic of this 

 region. Thus both the earthquakes and the volcanic eruptions have 

 the same ultimate cause and so are, in a sense, related. 



I cannot, however, agree with the author that these forces are 

 produced by the shrinkage of the globe from cooling, for I have 

 shown, I think, conclusively, that there has been no appreciable 

 ■diminution of the mean radius of the globe since Cambrian times. 

 These great forces producing elevations and subsidences, rock 

 foldings and earthquakes, and giving the conditions allowing volcanic 

 •action are, I believe, due to regional expansions and contractions. 



Neither can I favour the suggestion that there was a connection 

 between either of these seismic movements and an eruption of 

 Vesuvius ejecting an insignificant amount of material 6,000 miles 

 distant. 



We certainly owe our thanks to Dr. Warren Upham for presenting 

 us with his concise account of two memorable catastrophes. 



Col. T. H. Hendley, CLE. — Previous speakers, as well as the 

 writer of the paper, have referred to the rapidity of the trans- 

 mission of the earth tremors. Under certain circumstances the 



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