634 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



Mr. Joseph S. Wood read the following interesting paper, on 



The Internal Heat of the Earth. 



Many carefully made observations have determined the fact, 

 that the temperature of the earth increases at the rate of 1^ C. for 

 a depth of 30 metres, or 98^ feet. Supposing this rate constant, 

 the temperature of the earth, at a depth of 60,000 metres, or 37 

 miles, must be 2,000° C. As no substance is known to exist as 

 a solid at this temperature, the conclusion follows that the crust 

 of the glol)e is 37 miles thick, and the rest, beyond that depth, a 

 molten mass. 



To account for this condition of the earth, La Place advanced 

 the theory, that our solar system was a very thinly attenuated mass 

 of nebulous matter, which, by a rotatory motion, was drawn 

 too-ether in globular liquid masses; that these bodies have ever 

 since been and are now cooling, our earth having cooled suffi- 

 ciently to form the solid crust on w'hich we live. 



Upon this hypothesis are explained volcanic eruptions, earth- 

 quakes, gcyacYS, hot springs, the oblation of the earth at its poles, 

 the igneous formation of plutonic rocks, and the torrid climate 

 formerly existing in some portions of the Arctic zone. 



Notwithstanding its plausibility and simplicit}^ very grave 

 objections have been raised against it; and Lyell, together with 

 others, evidently accepts it simply from want of a better. 



If our solar system w^as created by the contraction of a nebulous' 

 mass, an immense amount of heat must have been radiated there- 

 from. 



As force cannot exist independently of matter, the question arises, 

 by what bodies was this heat absorbed? As the stars and nebula, 

 the only bodies outside of our solar system known to exist, are 

 sources of heat themselves, they evidently cannot be the absorbents. 



If all the bodies of our solar system were once masses of molten 

 matter, they must have radiated a portion of their heat in obtain- 

 ing solid surfaces; but not to one another, since, however, unequally 

 heated they may have been, they could not radiate heat to each 

 other, all being molten, so that the surfaces of all should solidify. 



If the earth is radiating heat, it must be contracting; but La 

 Place has shown that no contraction has taken place for at least 

 2,500 years. 



Mayer, in his Celestial Dynamics, asserts that if the earth's 

 interior is a molten cooling mass, it must, like all such bodies, be 



