﻿326 Canadian Record of Science. 



the vertical movement was unusually violent and rapid. 

 As a consequence of this, the record for one or two seconds 

 after the main shock is dotted. 



The minuteness of the motion of the ground in an 

 earthquake is at first sight rather surprising. There can 

 be no doubt, however, that these instruments record the 

 movement correctly, as they can be very easily tested, 

 and the theory is very simple. The profound impression 

 on the senses produced by an earthquake shock is due to 

 the irresistible nature of the motion and the immense 

 masses of matter affected by it. In the earthquake of 

 March 23rd, the maximum extent of the movement of the 

 ground is seen by the records to have been only about 

 one-fortieth of an inch. That of the very similar shock of 

 March 26th, midnight, was only one-hundredth of an 

 inch. These movements appear at first sight excessively 

 minute, but it appears from records of many other 

 earthquakes taken in a similar way that a vibration of 

 only a tenth of an inch, if sufficiently rapid and long 

 continued, may be exceedingly destructive, especially to 

 solidly founded buildings. 



Book Notices. 



Lakes of North America, a Reading Lesson for Students of 

 Oeography and Geology. — By Israel C. Russell, Professor of Geology, 

 University of Michigan. Ginn & Company, Boston and London, 

 8vo., pp. 125. 



Mr. Russell, who, for thirteen years, was connected with the 

 Geological Survey of the United States, and thus had ample opportunity 

 of carefully "studying the topographical features of various parts of the 

 continent, including Alaska, has, in this book, given in popular form a 

 description of lakes and their various relations, illustrating his 

 descriptions chiefly from the wealth of examples afforded by the lakes 

 of North America. 



Mr. Russell's original contributions to this field are extensive and of 

 the highest order, the most notable being his " Geological History of 

 Lake Labontan," which appeared as one of the monographs of the 

 United States Geological Survey, and his personal studies thus render 



