Astronomical and Nautical Collectiom. 127 



I V . Elementary view of theXJinDv l at ory Theory 0/ Li g h t . 

 By Mr. Fresnel. From the Supplement to the Trans- 

 lation of Thomson's Chemistry. 8. Par. 1822. 



[The Council of the Royal Society having adjudged, on 

 the 8th of February, Count Rumford's prize medal to 

 Mr. Fresnel, for his application of the undulatory theory 

 of light to the phenomena of polarisation, and this decision 

 having probably tended to give new vi^eight to that theory 

 in the estimation of the British public; it is apprehended, 

 that a translation of Mr. Fresnel's very distinct and well- 

 arranged statement, of the grounds of that theory, will not 

 be judged an improper article for insertion in the Nautical 

 and Astronomical Collections.] 



I. Nature of Light. 



The Nature of Light has long been a subject of dispute 

 among natural philosophers : some of them suppose that it 

 is a material substance, darted out by luminous bodies ; and 

 others, that it consists in the vibrations of an infinitely subtile 

 elastic fluid diffused through all space, in the same way that 

 sound is known to be a vibration of the air. The system of un- 

 dulations, which was contrived by the genius of Descartes, 

 and which was more ably completed in its detail by Huy- 

 GENs, has also been adopted by Euler, and in more modern 

 times by Dr. Thomas Young, to whom the science of optics 

 is indebted for many important discoveries. The system of 

 emission, or that of Newton, supported by the great name 

 of its author, and I might almost say, by that reputation for 

 infallibility which his immortal Frincipia had earned for 

 him, has consequently been more generally adopted. The 

 other hypothesis was apparently altogether abandoned, when 

 Dr. Young recalled the attention of philosophers to it by 

 some curious experiments, which afford a striking confirma- 

 tion of it, and which appear at the same time to be scarcely 

 reconcilable with the system of emission. 



A variety of new phenomena, observed since that time, 

 have continued to add to the probability of the truth of 

 the theory of undulations. Though long neglected, and 

 more difficult to be followed, in the detail of its applica- 



