of the Universe. 105 



motions. The elevated and mountainous parts of the planets 

 being repulsed by the continned action or resistance of the 

 gaseous medium, must produic a retardation also in tiieir rotatory 

 motions. An unequal rotatory motion must also be produced 

 in consequence of a variation of density in the planets, which 

 would retard their motions, when the hemisphere of preponde- 

 rating density was ascending from the sun, or rising into a su- 

 perior stratum, or rarer medium; I)Ut on descending towards the 

 sun, as on its opposite hemisphere, the contrary effect would 

 take place, so that an acceleration and retardation would result 

 alternately in every diurnal rotation of a planet, provided its 

 mathematical centre did not coincide with its centre of gravity. 

 In tact, uniform rotatory motions could not exist on this theory, 

 as a retardation would evidently predominate till the line passing 

 through the centre of each planet and the point of preponderating 

 density, acquired a relative position with the radii of their orbits. 

 The final results of their rotatory motions would he similar to 

 that of the moon in respect to the earth ; but which is sup- 

 posed to be retained in its relative position by the effects of their 

 mutual attractions, or principaHy by the attraction of the earth 

 on the paramount density on this side the lunar globe, so that 

 a revolution in its orbit and a rotation on its axis are performed 

 in the same period of time. 



S. We are informed, page 26, that the momenta in bodies 

 of equal densily in different strata or shells are inversely as the 

 squares of the radii. Ard the momenta of different densities in 

 the same strata are as the densities respectively. But the mo- 

 mentum in bodies of ecjual density in different strata must be di- 

 rectly as the radii, and not as tlie Sfjuares of the radii, as errone- 

 ously stated ; for the bulks being supposed equal in either case, 

 and their densities being equal, their masses must also be equal; 

 whence their momentum is compounded of their mass and velo- 

 city, which is directly as the radii. 



The densities and velocities of the planets in their orbits being 

 the same as that of the gaseous medium in which they circulate, 

 lieither the perturi)atinns in the inolions of the planets, satellites, 

 or comets, or their elliptic motions in their orbits, can be ac- 

 counted for on the above principles, as the essential properties 

 of bulk and momentum are the same in each planet, ns in spheres 

 of the medium under equal radii (in which the planets circulate), 

 and consecpiently can have no more efl'ect on the sun or on each 

 other, than the medium which they displace, or no mere effect 

 than if they did not exist. 



!). Page 2."). We are told that the wcreas'mg hulk in each 

 strannn h inversely as the cube of the radii. But tliis I deny. 

 For the diameter of the spherical strata, their bulk, velocity, 



Vol. 50. No. 2G8. ^w<'. 1820. O and 



