we have an analogy with what we see produced by circular mo- 

 tion of fluids, moving in one definite direction by a prime mover ; 

 the slower and more majestic movement corresponding with 

 greater dimensions of machinery, and thus impressing on us the 

 prevalence of an harmonious law of action and circular move- 

 ments, and not mere accidental compound of forces produced by 

 the casual meeting of two forces arbitrarily assumed. We know 

 that bodies may be sustained at any elevation in the air, as well 

 as in the ocean, by adjusting their densities to that of the stratum 

 of fluid in which they may be placed ; and that such bodies, 

 like the balloon in the air, or a vessel on the ocean, would con- 

 tinue to revolve uniformly round the earth by a circular current. 

 This is consistent with our daily experience, and according to the 

 well-known laws of nature. No one would presume to say that 

 the clouds are retained in their positions by means of centrifugal 

 forces, and that they would fall towards the earth if such forces 

 were removed. As nature is considered always conformable to her- 

 self, we have no right to assume powers different from those that 

 exist ; therefore we have no reason to suppose that the moon is 

 retained at her respective distance from the earth by a power dif- 

 ferent from that which retains the clouds. The moon, as well 

 as the earth, may be filled with hydrogen, or with still lighter gas 

 for aught we know to the contrary, and which is an opinion infi- 

 nitely more probable than that of its being filled with igneous 

 matter ; consequently a shell containing such a gas enveloped 

 with an atmospheric fluid, kept together by the magnetic at- 

 traction, would render the moon sufficiently buoyant to float on 

 the external part of the terrestrial fluid. 



On the established Laws of Motion as applied to the Heavenly 



Bodies. 



It is said that celestial bodies are not sustained in their orbits 

 like those we observe in terrestrial physics; they have laws 

 of motion peculiar to themselves, which have been assumed and 

 blended with the laws of geometry. Indeed, so far as physics 

 are concerned, it matters not much what hypothesis may be 

 adopted in astronomical phenomena, provided our calculations 

 be founded on uniform spaces, velocities, &c, as the whole are 

 reduced to the laws of proportion which subsist between sines 



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