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the fame proportion. Eut this alteration is much 
too fmall to difcover itfelf in the motions of the earth 
or any of the planets. I will not at prefent confider, 
by what law the diftance of the planets from the 
fun would increafe, becaufe the enquiry could not 
be reduced to a fmall compafs ; but it is obvious, that, 
whatever that law may be, it muff arife folely from the 
diminution cf gravitation : and the like is to be faid 
of the increafe of the anomalidic periods. And 
therefore, while the diminution of gravitation is in- 
fenfible, the changes in thefe circumdances mud be in- 
fen fible too. Of all the changes to which our fyftem 
may be obnoxious, thofe which fhould arife from 
the wake of the fun’s fubdance in light, upon the 
fuppofition that light is an aflual emanation of 
matter from the fun, reckoning that wade at the 
utmod, are perhaps the lead condderable. 
Jn the foregoing computations, the indantaneous 
emilTion of light has been greatly over-rated. For if 
the particles of light were of the magnitude and 
denfity which has been adigned to each, and were to 
idue from the fun in the clofe arrangement that has 
been luppofed, they would form a fort of crud 
upon the lun’s furface, at lead 12 times more denle 
than water, i. e. 9600 times moredenfe than our at- 
mofphere in the parts next the earth’s furface, if the 
denfity of common water compared to that of air 
be reckoned only as 800 to 1 k . But if the denfity 
of light upon the fun’s furface be 9600 that of our 
air, its denfity when it arrives at the earth, or its 
k It is well known that the denfity of water to that of air, is 
as 850 to 1 at lead. 
Vol, LX. I i i denfity 
