CHAPTER XI 



THE EXISTENCE OP THE ETHEREAL MEDIUM 

 TRANSMISSION OF LIGHT AND HEAT. 



IT has been mentioned that Newton considered 

 that Light was caused by material corpuscles emitted 

 from a luminous body and moving with an extreme 

 swiftness through the interstellar Ether, to which it 

 transmitted motion, and by which it ultimately 

 reached the eye of the observer. The action of 

 gravitation in causing the movement of bodies towards 

 each other, and of the planets and satellites in their 

 orbits, he thought was also due to the existence of such 

 a medium, filling all space. The doctrine of direct 

 action at a distance, by which one body could influence 

 another body not in contact therewith, nor with any 

 intermediate substance, in his opinion was absurd. 

 In his letter to Bentley he wrote : " It is inconceivable 

 that inanimate brute matter should, without the me- 



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