126 Dr. Young's Experiments and Inquiries 



and others transmitted, appears in this system to be wholly 

 inexplicable. That a medium resembling, in many properties, 

 that which has been denominated ether, does really exist, is 

 undeniably proved by the phaenomena of electricity ; and the ar- 

 guments against the existence of such an ether throughout the 

 universe, have been pretty sufficiently answered by Euler. 

 The rapid transmission of the electrical shock, shows that the 

 electric medium is possessed of an elasticity as great as is neces- 

 sary to be supposed for the propagation of light. Whether the 

 electric ether is to be considered as the same with the luminous 

 ether, if such a fluid exists, may perhaps at some future time be 

 discovered by experiment; hitherto I have not been able to 

 observe that the refractive power of a fluid undergoes any 

 change by electricity. The uniformity of the motion of light in 

 the same medium, which is a difficulty in the Newtonian 

 theory, favours the admission of the Huygenian; as all impres- 

 sions are known to be transmitted through an elastic fluid with 

 the same velocity. It has been already shown, that sound, in 

 all probability, has very little tendency to diverge: in a medium 

 so highly elastic as the luminous ether must be supposed to be, 

 the tendency to diverge may be considered as infinitely small, 

 and the grand objection to the system of vibration will be 

 removed. It is not absolutely certain, that the white line visible 

 in all directions on the edge of a knife, in the experiments of 

 Newton and of Mr. Jordan, was not partly occasioned by the 

 tendency of light to diverge. Euler's hypothesis, of the trans- 

 mission of light by an agitation of the particles of the refract- 

 ing media themselves, is liable to strong objections ; according 

 to this supposition, the refraction of the rays of light, on entering 

 the atmosphere from the pure ether which he describes, ought 



