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SCIENCE PROGRESS 



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TIDES AND THE RIGIDITY OF THE 



EARTH 



By PROF. A. E. H. LOVE, F.R.S. 



The publication of a third edition of Sir G. H. Darwin's well- 

 known semi-popular book on the Tides 1 affords an opportunity 

 of forming an estimate of the advances that have been made in 

 recent years in knowledge concerning all those geophysical 

 phenomena which either are directly due to the forces that 

 cause the tides or share with these direct effects some feature 

 rendering them amenable to discussion by similar methods. 

 Sir G. H. Darwin is the greatest living authority on these 

 questions and the fact that nearly one quarter of the third 

 edition of his book is either added or rewritten is sufficient 

 evidence that substantial advance has been made. This advance 

 is not confined to the theory but extends also to the methods of 

 observation and the devising of suitable instruments, besides 

 including a very great increase in the mass of records that are 

 available for the comparison of theoretical results with observed 

 facts. On the purely observational side, perhaps the greatest 

 novelty is to be found in the beginning of actual measurements 

 of the range of the tide in the open sea. On the purely 

 theoretical side, the modifications of Laplace's nebular hypothesis 

 which have been suggested by various writers are specially 

 attractive. But the advances that will prove most interesting to 

 many readers have been made by combining theoretical con- 

 siderations with observational results in regard to several 

 groups of phenomena from which conclusions have been drawn 

 as to the internal constitution of the Earth. We propose to 

 consider these matters in order. 



1 The Tides and Kindred Phenomena in the Solar System, by Sir George 

 Howard Darwin. Third Edition. London : John Murray, 191 1. 



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