THE PLAN OF THE EARTH AND ITS CAUSES. 387 



crust would undergo tetrahedral deformation, and the evidence of 

 geodesy shows that the earth has been deformed from its spheroidal 

 form. Its present figure may be defined as a geoid, which has been 

 derived from a spheroid by irregular tetrahedroid deformation. 



If such tetrahedral collapse be granted in the case of the earth, then 

 the existing arrangement of oceans and continents receives a natural 

 explanation. 



The changes in the distribution of land and seas in the past may be 

 explained as due to the conflict of two opposing forces, collapse caused 

 by the earth's contraction producing deformations, which are reduced 

 by the effects of the earth's rotation. Geological history affords evi- 

 dence of the alteration of periods of tetrahedral collapse and spheroidal 

 recovery. 



The plan of the earth may, in short, be attributed to the continual 

 foundering of the earth's external shell, owing to the unceasing shrink- 

 age of its internal mass. 



After the reading of the paper, the President said: In inviting the 

 discussion of this paper, I believe that there are those here who have 

 given some thought to the subject, and who will at least be inclined to 

 tell us what their impressions are respecting the views set forth in Dr. 

 Gregory's paper. I hope Sir John Murray for one will be disposed to 

 give us the result of his impressions on the subject, and also Mr. 

 Blauford. 



I find there is a reluctance on the part of learned men to commit 

 themselves to any opinions on a question which at present is in its 

 infancy, and on which their views are not entirely settled. I think 

 that some parts of the paper might have been discussed, and I can not 

 help expressing, as I have done on other occasions, my regret at the 

 loss we have sustained in our lamented friend General Walker, for 

 there is no man who could have spoken with so much authority on one or 

 two points, especially on the very slight differences that have occurred 

 between astronomical observations and geodetic measurements. As 

 Mr. Whittaker, the president of the Geological Society, is present, 

 perhaps he would be disposed to address us. 



Mr. Whittaker. I came to listen, not to speak. I found a little 

 time ago that many gentlemen have come here after having the pleasure 

 of seeing the proof. I am not one of those, and were I to speak, it would 

 be without the advantage they have had ; consequently they would have 

 the pleasure of sitting upon me, and this goes against my feelings. I 

 would offer one general remark — it is the satisfaction I feel with any 

 paper of this sort that shows the interdependence of the various sci- 

 ences, and how men who follow one branch of science should not have 

 too much of that branch alone, but should see occasionally how it bears 

 on others, and, on the other hand, how others bear on it. This calls in 

 geologists, physicists, mathematicians, and many others, and it is too 



