RED RAY NOT REFLEXIBLE. 65 



and even animals, also, in the color of their hair, are influenced 

 by the same power, as may be proved by comparing the polar 

 and tropical animals, and the parts of their bodies exposed to, 

 and excluded from, its presence. 



The discoveries of Newton respecting the modifications of 

 light by double reflection and refraction, have, for a time, set 

 aside the hypothesis supported by Hooke, Huygens, and Euler, 

 as to the supposed existence of a rare elastic substance, which, 

 by undulation, produced the sensations of vision. As the co- 

 lored rays separated by the prism bear the same relation to 

 double refraction that direct light bears, it follows that the po- 

 larity of the different particles must be of the same kind, as 

 mentioned by Sir H. Davy ; who also remarks, that Newton 

 attempted to explain the different refrarigibilities of the rays 

 of light by supposing them to be composed of particles differ- 

 ing in size ; and he states that this hypothesis is not contra- 

 dictory to the idea of their being regular solids endowed Avith 

 similar polarities. The same great man (Newton) put the 

 query, Whether light and common matter are not convertible 

 into each other ? and, adopting the idea that the phenomena of 

 sensible heat depend upon vibrations of the particles of bodies, 

 supposed that a certain intensity of vibrations may send off par- 

 ticles into free space ; and that particles in rapid motion in 

 right lines, in losing their own motion, may communicate a 

 vibratory motion to the particles of terrestrial bodies. 



The rays of light materially differ in their refrangibility, 

 calorific power, and intensity of illumination. 



The red ray is the most reflexible and least refrangible. 

 The blue and violet rays the least inflexible and most refran- 

 gible ; the others in the order in which they stand in the spec- 

 trum. When light passes within a certain distance of a body 

 parallel to which it is moving, it is bent towards that body ; 

 this property is termed inflection ; when it passes at a greater 

 distance it is bent from it, which is called deflection. Now 



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