KINETIC THEORIES OF GRAVITATION. 241 



medium follows the law of the inverse square of the distance from the 

 center of disturbance. 2d. The resistance of the tether does not sensi- 

 bly affect the velocity of a body when this is sufficiently less than that 

 of aetherial propagation ; but this resistance becomes a uniform pressure 

 on the entire surface of a body, (supposed spherical.) and even deter- 

 mines its sphericity. 3d. Taking as unity the density of the fluid, the 

 quantity of motion impressed by a body on the aether is equal to its 

 volume multiplied by the square of its velocity ; which is also the meas- 

 ure of the total pressure on the surface of a body. 4th. Propagated to 

 the interior of the heavenly bodies, the pressure would produce the 

 effect that all layers of equal thickness will inclose the same quantity of 

 matter, and that the mean density is three times that of the surface. 

 This kind of homogeneity would not be affected by the action of heat. 

 In short, from such great internal condensation, it may be conjectured 

 that the heavenly bodies are almost entirely impermeable by the aether, 

 as will shortly appear from an astronomical law. 5th. As to attraction; 

 the displacement of the a?ther by the movement of a body A, will pro- 

 duce in all parts of the fluid a sort of aspiration toward the point being 

 left by its center; any other body B receiving these aspiring waves on 

 its nearer hemisphere wi.l have lost all or a part of its owu pressure; 

 and the half pressure (volume multiplied by the squared velocity) which 

 acts on the opposite hemisphere, no longer being counterbalanced, will 

 give an impulse to the body B in the direction of A. Such would be 

 the principle of attraction. ..." 



The writer finds a verification of his principles in the relation existing 

 between the respective masses of the planets and the product of their 

 volumes by the square of their velocities, omitting the cases of Uranus 

 and Neptune. Also by determining the velocity of an attracting body 

 from that of its satellite, knowing only the ratio of the radius to the dis- 

 tance; aud lastly, by determining the amount of fall of heavy bodies 

 from the angular velocity of the earth, irrespective of its mass!* 



Lame. 1852. 



Gabriel Lamd, a distinguished French geometer, and author of a very 

 learned and valuable woik on the laws of elasticity, embracing a pro- 

 found mathematical discussion of the theory of vibrations in almost all 

 its scientific aspects, has incidentally alluded to gravitation in such a 

 manner as to deserve a notice here. 



Ofhis more immediate themehelorcibly remarks: ''Elasticity is thereat 

 origin or indispensable intermediary of all the more important physical 

 phenomeua of the universe. . . . In a word, the function of elasticity 

 in nature is at least as important as that of universal gravitation. 

 Indeed gravitation and elasticity should be considered as effects of the 

 same cause, which correlate or connect all the material parts of the uni. 



* Comptes Ilendus, July 30, 1H49, vol. xsix, pp. 108-112. The author embodied his 

 views in a work entitled Principe Ueue'rah de la PMlosaphie Katurelle, Svo, Paris, 1653. 



s 1G 



