640 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



hence the book is now acted on hy a smaller force of gravity than 

 before it fell. 



The greater the distance between two bodies the greater the 

 kinetic forces acting on them. Herein lies tiie answer to the 

 question, what becomes of the gravity set free from the book? 

 The answer is, it is transferred to the atoms or molecules of sur- 

 rounding bodies, and converted into the force of cohesion. 



AVhen the book fell, not only was heat transferred to the sur- 

 rounding matter, but the atoms of the latter were separated from 

 each other by expansion. Indeed the fact that heat producer 

 expansion, proves that an increase of heat must be accompanied 

 with an increase of attractive force. 



The force of cohesion acts upon the atoms or molecules of all 

 substances, tending to draw them together, and the force of gravity 

 acts upon all the heavenly bodies in the same way. Since they 

 are not drawn together, they must be kept apart by a force of 

 repulsion, exactly equal to the force of attraction. Since, when 

 the atoms of a body are drawn together, heat is set free; the con- 

 clusion follows, that it must have been previously existing in the 

 body, in a kinetic state; and since an equal amount of the force of 

 cohesion is also let loose, the heat and the cohesive force must 

 have been holding each other hi eqmlihno. Indeed no force can 

 be kinetic, unless held in equilihrio by another; and the true 

 cause why the earth is not drawn into the sun, as well as why two 

 molecules do not touch, is not the centrifugal force, but the force 

 of heat. 



As a test of this theory that the internal heat of the earth i^ 

 caused by gi-avity, I proposed, in a draft of this paper, written in 

 January, 18G5, the following: If the oarth's interior is a molten 

 mass, the waters of the'ocean should be undergoing a process of 

 convection similar to that of the water in a tea kettle over a lire; 

 and the temperature of the whole should l)e the same for all 

 depths. If, on the other hand, it is caused l)y gravity, then no 

 process of convection should be going on; and the temperature 

 should increase with the depth. Since that time I have met with 

 the following paragraph in Mayer's Celestial Dynamics: " Frank- 

 lin observed in lat. 77° N., long. 12° E., that the temperature of 

 the sea near the surface was — -^°, and at the depth of 700 fathoms 

 6°. Fisher in hit, 80° N., long. 11° E., noticed that the surface 



