88 BISSERTATION SECOND. 



[J-ART II. 



convex and concave toward the knife, according to the 

 repulsive or attractive forces which acted at different dis- 

 tances ; that it was also reasonable to conclude, that the 

 phenomena of the refraction, reflection, and inflexion of 

 light w T ere all produced by the same force variously modifi- 

 ed, and that they did not arise from the actual contact or 

 collision of the particles of light with the particles of bodies. 



The Third Book of the Optics concludes with those 

 celebrated Queries which carry the mind so far beyond the 

 bounds of ordinary speculation, though still with the sup- 

 port and under the direction either of direct experiment or 

 close analogy. They are a collection of propositions rela- 

 tive chiefly to the nature of the mutual action of light 

 and of bodies on one another, such as appeared to the 

 author highly probable, yet wanting such complete evi- 

 ence as might entitle them to be admitted as princi- 

 ples established. Such enlarged and comprehensive views, 

 so many new and bold conceptions, were never before 

 combined with the sobriety and caution of philosophical 

 induction. The anticipation of future discoveries, the as- 

 semblage of so many facts from the most distant regions of 

 human research, all brought to bear on the same points, and 

 to elucidate the same questions, are never to be sufficiently 

 admired. At the moment when they appeared, they must 

 have produced a wonderful sensation in the philosophic 

 world, unless, indeed, they advanced too far before the age, 

 find contained too much which the comment of time was yet 

 required to elucidate. 



It is in the Queries that we meet with the ideas of this 

 philosopher concerning the Elastic Ether, which he con- 

 ceived to be the means of conveying the action of bodies 

 from one part of the universe to another, and to which the 

 phenomena of light, of heat, of gravitation, are to be ascrib- 

 ed. Here we have his conclusions concerning that polarity 



