1866.] 15 [Shaler. 



in order that any considerable elevation be formed by this action, it 

 would be necessary to have the upper and lower beds slide one upon 

 another, to a certain extent ; but it is to be borne in mind that the 

 power we are hypothecating is practically illimitable, since it would, 

 by the supposition, continue to accumulate until the force became 

 sufficiently great to overcome resistance. The sliding of beds upon 

 each other under the influence of great lateral pressure from the con- 

 traction of the lower portions of the crust, has fewer objections to be 

 urged against it, than the view which assigns the origin of mountain 

 chains to the passage of great waves of translation through the crust, 

 and their fixation by the intrusion of molten matter. 



It is scarcely necessary for the author to state, that no claim what- 

 ever is meant to be made in this paper, to the hypothesis of the origin 

 of the featsires of corrugation of the crust from the influence of con- 

 traction from loss of heat; one of the oldest and most generally 

 accepted theories of the science. It having been denied by verv 

 high authority that there existed any cause competent to produce 

 lateral thrust, and thus to originate mountain chains, it has seemed 

 desirable to direct attention to the fact that the recession of the isogeo- 

 tbermals would be attended by such lateral strain. 



The points which have been suggested in the foregoing considera- 

 tions, may be briefly summed up as follows : 



1. That the most probable hypothesis in the present state of our 

 knowledge of the earth, is, that it consists of an immense solid 

 nucleus, a hardened outer crust, and an intermediate region of com- 

 paratively slight depth, in an imperfect state of igneous fusion. 



2. That the continental folds are probably corrugations of the 

 whole thickness of the crust, 



3. That mountain chains are only folds of the outer portion of the 

 crust caused by the contraction of the lower regions of the outer 

 shell. 



4. That the subsidence of ocean floors would, by producing frac- 

 tures and dislocations along shore lines, tend to originate mountain 

 chains along sea borders, and approximately parallel to them. 



June 20, 1866. 



The President in the chair. Twenty-seven members present. 



Before proceeding to the ordinary business of the meeting, 

 the President stated that tlie Society had recently lost two 



