1835.] Scientific Intelligence. 315 



curried from Gard arid Ardeche. At Herault it may be obtained at 

 Cruzy, Quarantc, Calzouls, Herepian, Beziers, Clermont, Loubes, 

 and Lodeve. It is extensively employed in Canada with the most 

 happy results. It was tried in Yorkshire by Lord Dundas without 

 any benefit, but the soil upon which it was spread was ascertained to 

 contain a quantity of gypsum. It might be employed, there can be 

 little doubt, with great advantage in the border counties, where the 

 trifolium pratense has in many places failed. This plant neces- 

 sarily from its strong and luxuriant nature, obviously must require 

 a considerable quantity of the manure. If it be deficient in quantity 

 the plants may vegetate, but must speedily perish from the effect of 

 the first frost on their delicate structures. 



II. — Royal Institution. — Comparison of the Newtonian and 

 Undulatory Theories of Light. — 30th January. 



Dr. Ritchie commenced his lecture on the two theories of light 

 which have been advocated by different philosophers for many years, 

 with a few observations with regard to the difficulty of acquiring 

 knowledge of the subject by direct experiment, in consequence of the 

 almost spiritual nature of the substance upon which it is necessary 

 to operate. 



Newton whose opinion was long in vogue, having had his atten- 

 tion directed to the motions of bodies, considered light as a sub- 

 stance consisting of revolving spherical particles issuing from luminous 

 bodies moving in straight lines, and producing reflection or re- 

 fraction according as the extremities of the spheres, which came in 

 contact with a denser- medium, were sharp or obtuse. This theory 

 required certain postulates which appear, however, to be entirely gra- 

 tuitous. By the undulatory theory, which is often called the theory 

 of Huygens, which was suggested to his mind in consequence of Ins 

 attention being directed to the motions of the pendulum, although it 

 was known before his time, light is considered to consist of the 

 undulations of an ethereal fluid filling all space, and existing between 

 the particles of bodies. If such a fluid does exist, we might expect 

 that it would act in retarding the motions of the heavenly bodies. 

 It is obvious, however, that the planets can suffer no retardation, 

 because, in consequence of their revolutions, the ether will also acquire 

 motion and be carried along with them, but in reference to the comets, 

 which are extremely light bodies, we find a decided retardation, which 

 after making all allowances, can only be accounted for on the sup- 

 position of the existence of an etherial medium. This has been 

 clearly proved by Sir John Herschel, in his article on light in the 

 Encyclopaedia Metropolitana. Dr. Ritchie stated that he had only be- 

 come a convert to the undulatory theory of light about two years 

 ago, in consequence of Herschel's arguments, and an attentive com- 

 parison of the two theories. This ether, then, is supposed to exist in 

 the pores of all bodies, being more dense in solid bodies than in 

 empty space, but possessing less elasticity. An impulse being given 

 it, a succession of waves is produced, precisely like sonorous vibrations 

 which strike upon the retina and cause that membrane to move back- 

 wards and forwards, or vibrate, as the undulatory motions of the air, 



