PHYSICS OF THE GLOBE. 



By CLEVELAND ABBE, 



Of the Aeaiy Signal, Office. 



THE EARTH.* 

 INTERNAL CONDITION. 



Professor H. Hennessy read before the British Association, 

 at Dublin, an important paper on the Limits of the Hypoth- 

 eses regarding the Properties of the Matter composing the 

 Interior of the Earth. He maintains that the views long ago 

 proposed by himself, in opposition to Hopkins, are those that 

 now are coming to be generally accepted : that the mathe- 

 matical investigations of Hopkins, Thomson, Darwin, etc., 

 have little or no bearing upon the question, because these 

 authors have assumed an incompressible homogeneous fluid 

 nucleus to be surrounded by a solid elastic compressible 

 shell; whereas we now know that the fluid nucleus is vastly 

 more elastic than its rocky envelope a reversal of conditions 

 that entirely changes the problem. He finds evidence in the 

 most recent writings of Thomson and Darwin of these more 

 correct physical views. 



A comparison of the diverse views of modern scientists 

 upon the condition of the interior of the earth is given by 

 Dr. F. Toula, in a lecture published in Vienna. 



In a recent address, Sir G. B. Airy inferred from observa- 

 tions on internal temperature, and from the phenomena of 

 hot springs and volcanoes, that " a large proportion of the 

 interior of the earth is fluid and hot," and that this is sur- 

 rounded by a solid crust of varying thickness and density, 

 traversed by cracks which afford opportunities for volcanoes 

 to burst forth where the crust is thin. 



* Prepared with the assistance of Prof. C. G. Rockwood, of Princeton, N. J. 



