434 The PhtBnomena of Gravitation proved to be proximate 



strayed each other, the body is then surrendpred to the joint ac- 

 tion of the Grhlcul or force and. the rotary force. 



8. And we have seen that it is the effect of the rotary force 

 to deflect it Jrom the right line of the or bic2ilar force towards 

 tilt earth. 



Coiiseqiieiitlv it is the rotation of the earth and atmosphere, 

 acting simultaneously with the annual motion, which produces 

 the deflection of bodies from the ri,2;ht line of their orbicular 

 motion; but the circular rotation has another important effect 

 on the masses of various density which compose the earth, and 

 which, as subject to a common force, would have different orbi- 

 cular velocities, but for the effect of their common rotary motion 

 in circles of different radii*. 



To thQ rotary motion of the earth is, therefore, to be referred 

 that uniformity in the velocity of bodies of various density, which 

 enables the whole to keep an equal and uniform pace in the or- 

 bit of the earth. It is this rotary motion which reduces to order, 

 what otherwise would be chaos. Hence it is that all fluids are 

 impelled into a level surface ; hence too, doubtless, it has been, 

 that masses of the same density have formed themselves into 

 strata while in a state of solution ; hence arise all the phseno- 

 mena which result from anv disturbance in the order of density ; 

 and hence it is that, when a heavy body is thrown into lighter 

 fluids — as air or water — tlie general law is proved by phaenomena 

 exactly proportioned to the relations of density. 



We know, from the diurnal phasnomena, that the earth and 

 atmosphere have such a common rotary motion ; and we know, 

 from their common orbicular force, that the whole have unequal 

 momenta. It is, however, a necessary mechanical effect of a 

 common rotary motion, producing, of course, equal momenta in 

 masses of various density that they range themselves, or seek to 

 range themselves, in concentric circles, or radii of rotation, in- 

 versely, as their respective densities. The lighter bodies will be 

 projected from the centre towards the circumference, and the 



* It seems extraordinary tliat, although the two- fold motion of tiie earth 

 has so loiii^ been kno.vn and admitted, nu mechanical effects shouhl 

 have heen considered as arising amonc; its parts from the ojieration of tlioje 

 motions; and that one motion should have been considered as having rju 

 other end tliun the alternation of se:isons,and the other none hut tlie chan|:;( j 

 of day and nit;ht. It 3 true that these are some of the ends resulting from 

 the tvvo-l'old motion ; bat general causes have many effecte, and these are 

 rather constqucntinl tiian proximate. Tlie proximate etfect of motion is 

 force; the proximate; effect of force is the communication of motion, force, 

 ami momentum : and in this instance the motions of the earth produce in 

 the parts motion, force, and monientu : which, diverted, deflected, or turned 

 aside, by any foreign muscular, mechanical, or explosive force, produce 

 l^c phxaomeaa of resistance and weight. 



heavy 



