54 WAREEN UPHAM, M.A._, D.SC._, F.G.S.A., ON THE SAN FEANCISCO 



they are being rebuilt on better foundations and with greater 

 foresight and effort for durabiUty and safety than before. Then 

 if the terrifying tremor comes again, the brave citizens will be 

 conscious that they have done their best and are in the path 

 and place of duty. The earthquake is more likely to try the 

 quality of these people again than if they should remove to 

 many other parts of the world ; but no region on all its surface, 

 though long remaining unshaken, can be assured of complete 

 immunity from this danger. 



The thanks of the meeting were then moved hy the Chairman for 

 this interesting communication, and he invited discussion thereon. 



Discussion. 



Rev. A. Irving, D.Sc, congratulated the Institute on the valuable 

 paper by Dr. Warren Upham, and thanked the author for putting 

 forward so clearly the causal relation of earthquakes of the San 

 Francisco and Valparaiso type to those tectonic forces which are 

 operative as mountain-building agents, which of necessity continue 

 more active in such comparatively young mountain ranges as those 

 which mark the features of the Pacific seaboard of the dual American 

 continent. The speaker confessed, however, to some feeling of regret 

 that more recognition had not been given to previous literature 

 bearing upon the subject. He referred more especially to the 

 writings of his friend, Dr. Andrew C. Lawson, the Chairman of the 

 Commission appointed by the Californian State authorities, after 

 the San Francisco earthquakes in April last, to investigate the 

 causes of that disaster. He held in his hand, and read quotations 

 from, a most able paper by Professor Lawson, on " the Geo- 

 morphogeny of the Coast of North California," in which it was 

 clearly shown, some twelve years ago, that the basin of the harbour 

 of San Francisco was formed l)y a subsidence — a "sag-down," as 

 engineers would say — of the crust in Quaternary and recent 

 geological time, letting in tlni waters of the Pacific to fill the 

 shallow basin (nowhere more than 250 feet in depth), submerging 

 the lower portion of the valley of the Sacramento, and converting 



