ON GRAVITATION. 22$ 



the series, with 4- &c.» meaning, of course, that the other 

 series and terms were to be supplied, as I before remarked, 

 and which it is strange Mr, D. should have forgotten. And 

 secondly, I have never mentioned, nor was it possible I 

 could mention, that the two terms alluded to are sufficient 

 to determine the force: a further proof with what little at- 

 tention Dytiscus has read the essay. 



Again, he says, " the series -^ 4, -1 -f -1. -j- &c. may cer- An assertlonof 

 o- fi o, his etfoaeotts, 



tainiy vary as — , if all the Greek letters after the first be- 

 come inconsiderable, and our author has virtually confessed 

 in his essay, that they do become inconsiderable." The se- 

 ries certainly can not vary as — . The quantities $, y, &c. 



are very small, but still finite, and can only be rejected in 

 an approximation to the law of force. The law of gravity 



varies accurately as — , and the series can never give that 



law, as I have proved in Art. 11. 



Farther: ** As to the difficulty of extending the law to Another con- 

 the internal parts of the sun's substance, it is perfectly ob- ^^'^^'^^ 

 vioiis, that the law of density, as well as that of the force, 

 must be supposed to change at the surface of every material 



Q 



body, long before — can become equal to P." Not per- 

 fectly obvious. When we discover sudden variations of the 

 laws of nature, it is not that the primary cause is necessarily 

 altered, but that some of the circumstances under which it 

 acts are changed, as in the present instance. Without con- 

 sidering the cause, we know, that the attractions of every 

 two particles of matter composing the sun's body vary in- 

 versel} as the squares of their distances, and at the same 

 time constitute a whole force, v/hich, to a body external to 



the sun, varies as — , and to an internal body, as a. It is 

 a* 



not therefore necessary, that the law of attraction of the 

 constituent particles should vary, in order to produce thes« 

 different laws of force. According to Newton, any two par- 

 ticles 



