ig ESSAYS anv OBSERVATIONS 
from the vifible object to the eye, may 
perhaps remove the difficulty by afcri« 
bing a fuflficient minutenefs to the parti- 
cles of that medium; fince we fee, by ex- 
perience, that found in the air, and waves 
in the water, are conveyed in different 
directions, without fenfibly interfering: 
But, as that hypothefis feems infupport- 
able on other accounts *, we mu‘ endea- 
vour to accommodate our folution to the 
only other conception we can frame of 
it; namely, that of particles aétually 
projected from the luminous body. 
3. Iv is manifeft, that, though the 
mere fubtility of the particles of light 
may tend to account for its eafy paflage, 
in all directions, through denfe tranfpa- 
rent bodies, it will not ferve to explain 
‘its eafy paflage through other light equal- 
ly fubtile: But, for this purpofe, it feems 
neceflary to fuppofe light incomparably 
rare when at the denfeft ; that is, that 
* Newtcni principia, book 2, prop. 41. and 42. Seealle 
Newton's optics, query 28, 
the 
