UNIVERSAL GRAVITATION. 19 



was thus laid open to the world, I need scarcely hint ; 

 yet who can be entirely silent on so magnificent a 

 theme ? The earth, the sun, and all the celestial 

 bodies which attend the sun, attract each other mutu- 

 ally. The minutest particles of each of them, and of 

 all other bodies, conform to the same law ; each par- 

 ticle acting proportionally to its quantity of matter 

 directly, and to the squares of its distances from other 

 particles reciprocally. Hence flow a variety, not yet, 

 nor perhaps ever to be, exhausted, of interesting and 

 important propositions. Such, for example, as those 

 which relate to the attraction of spheres, spheroids, and 

 other solids, whether homogeneous or not, upon parti- 

 cles in assigned positions ; the forces which retain the 

 planets in their orbits, so as to conform to the Keplerean 

 laws ; the forces which disturb the elliptic motions of 

 the planets and satellites ; the irregularities of the lunar 

 motions, and those of the other secondaries ; the muta- 

 tions of the planes of the several orbits ; the figure of 

 the earth and planets; the variations of gravity at 

 different points on their surfaces ; the tides ; the 

 oscillations of the atmosphere ; the variations of atmo- 

 spheric pressure at different altitudes ; the refraction of 

 light while passing through the atmosphere ; the attrac- 

 tions of mountains ; the precession of the equinoxes, 

 and the nutation of the earth's axis; the irregular 

 figure and balancing of Saturn's ring, and the dependence 

 of that balancing upon that irregular figure ; the libra- 

 tion of the moon ; these and many more topics of 

 investigation springing from the theory of attraction, 

 and each and all of them, as they are pursued, supplying 

 greater or less confirmation of the existence, " the sim- 

 ple and sublime agency, of this commanding principle." 



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