14 ESSAYS AND OBSERVATIONS 



nefs to the particles of that medium ; fincc 

 we fee, by experience, that found in the air, 

 and waves in the water, are conveyed in dif- 

 ferent diredions, without fenfibly interfe- 

 ring : but, as that hypothefis feems infup- 

 portable on other accounts *, we muft endea- 

 vour to accomrnodate our folution to the on- 

 ly other conception we can frame of it ; 

 Ijamely, that of particles adually projeded 

 from the luminous body. 



3. It is manifeft, that, tho' the mere fub- 

 tility of the particles of light may tend to ac- 

 count for its eafy paiTage, in all diredions, 

 thro' denfe tranfparent bodies, it will not 

 ferve to explain its eafy paiTage thro' other 

 light equally fubtile : but, for this purpofe, 

 it feems necelTary to fuppofe light incompa- 

 rably rare when at the denfefl ; that is, that 

 the femi-diameters of two of the neareft 

 particles in the fame or in different rays, foon 

 after their emiffion, are incomparably lefs 

 than their diffcance. 



. 4. Let us confider a little the courfe of a 

 particle of light from any of the remoter fix-* 



ed 



* Neiotom Prindpia, book 2. prop. 41. and 42. See alfo 

 ^ew/oji^s Optics, query 28. 



