ON THE FIXED STAIIS. '" 485 



these bodies will be superficially indicated; their sensible effects with respect 

 to the inhabitants of the earth will be shown, and the practical modes of 

 determining their situations and orbits will be explained. 



When we begin to consider,on a large scale, the affections of matter and of 

 space, we are impressed, at the first sight, with the inconceivable disproportion 

 between the magnitude of space and of sensible matter : and we are naturally 

 led to inquire if the apparently void expanse of the universe is wholly with- 

 out all matter or all substance. The atmospheres of the planets cannot 

 indeed be said absolutely to terminate at any given point, but they must become 

 iare beyond all imagination at a very moderate distance. The substance which 

 produces the sensation of light must, -however, be every where found, at 

 least without any sensible interval: for if an eye were placed in any point of' 

 the regions of unbounded space, wherever human investigation or fancy 

 can penetrate them, some luminous object would at each instant be visible to 

 it, and, in general, objects without number might be seen in every direction. 

 Light, therefore, must be every where present, whether we suppose it to 

 consist of separate projected corpuscles, or to be an affection of a highly 

 clastic ether, pervading the universe in a state so rare, that although it 

 constitutes a continuous medium, it suffers all bodies to move through it 

 without sensible resistance, and is admitted even into their pores with per- 

 fect freedom; and if we follow Newton's opinion of the nature of light, wc 

 must suppose both such an ethereal medium, nearly at rest, and the particles 

 of light also, moving swiftly through it, to exist together in all places: to 

 say nothing of the possibility of the coexistence of a thousand other unseen 

 and unknown substances, essences, and influences, in the same individual 

 place, which may for ever set at defiance the pride of a presumptuous phi- 

 losophy, that would aspire to comprehend, within its own contracted sphere, 

 the whole extent of the mighty work of the creation. 



The expanse of the universe is strewed, at immense distances, with detached 

 portions of a substance, which we suppose to be matter, constituting stars, 

 or suns, planets, and comets; bodies which certainly agree with each other 

 in the power of emitting or reflecting light, and which, in all probability, have 

 many other properties in common. Such of these, as emit their own light, are 



VOL.. I, 3 R , 



