VOL. LX.|] PHILOSOPHICAL TRANSACTIONS. (Jjt 



force of motion, which, instead of exceeding the force of a twenty-four pounder, 

 discharged from a cannon, is infinitely less than that of the smallest shot dis- 

 charged from a pocket pistol, or less than any that art can create. 



I proceed to the other questions. — And, I think, tliat I shall make it appear, 

 that it is very possible that light may be produced by a continual emission of 

 matter from the sun, without any such waste of his substance as should sensibly 

 contract his dimensions, or sensibly alter the motions of the planets, within any 

 moderate length of time. Indeed, I do not think it necessary to the production 

 of any of the phenomena of light, that the emanation from the sun should be 

 continual in a strict mathematical sense, or without any interval. It seems suffi- 

 cient to all purposes, that the intervals should be exceedingly short. But this I 

 only mention. — I think it possible that a continual emanation might subsist, 

 without any such dangerous consequences to the solar system, as Dr. Franklin 

 apprehends. Dr. Franklin's character is not more distinguished by his superior 

 talents, than by a candor truly philosophical. And on this circumstance I build 

 the strongest confidence, that he will not be ofl^ended, that I differ from him: 

 that, as a friend to inquiry, he will be pleased that I take the liberty to commu- 

 nicate my own notions, however opposite they may be to his. 



It will be easily understood, that a continual emanation from the sun does not 

 necessarily imply a continual waste, or loss, equal to the emanation. — If light is 

 continually issuing from the sun in all directions, part of this is continually 

 returning to him, by reflection from the planets, and other light is continually 

 coming to him, from the suns of other systems. It is true, that the light which 

 he receives, is but a very small part of the light which he gives. For if the light 

 always coming to the sun were equal to the light always going from him, our 

 atmosphere would be as strongly enlightened in the night as in the day. — But 

 this is not the case; and the proportion of the light that comes, to the light 

 that goes, cannot be greater than that of night-light at a medium, to day-light 

 at a medium — still it is something — and the continual loss of substance that the 

 sun sustains cannot be more than the difference between the light that he gives, 

 and the light that he receives. And therefore, if there were no other recruit of 

 the sun's substance (which is by no means a probable supposition) yet the conti- 

 nual waste will, on this account alone, be less than the continual emission ; and 

 the sun cannot lose so much of his substance as a single emission of light con- 

 tains, but in some determinate time. 



I shall suppose that the sun gives so much more than he receives, that he loses 

 the amount of one emission in every second of an hour. Let us see what will 

 be the consequence. Every particle of light that issues from the sun, must leave 

 a spherical vacuity of one millionth of one millionth of an inch diameter. The 

 greatest number of particles of this size that can issue from the surface of the 



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