ON THE RAYS OF LIGHT. 297 



veral colours c, called the prismatic colours. The 

 spectrum, as it is termed, thus formed, consists 

 of seven colours ; that which is least refracted be- 

 ing red, and in succession orange, yellow, green, 

 blue, indigo, and violet. If these rays be re- com- 

 pounded by passing through a convex lens, which, 

 owing to the obliquity with which they fall, draws 

 them to a point, the focus of the light will be again 

 colourless. Some modern philosophers have re- 

 duced these prismatic colours of Newton to three 

 primary colours, red, yellow, and blue ; contriv- 

 ing, by the super-position of these, to produce the 

 seven tints ; while others have, on considerations 

 not easy to be disproved, held that there is not 

 any definite number of colours, but a gradation of 

 tints, from the extreme red to the extreme violet. 



We may now understand the reason of the co- 

 lour of objects. When light strikes upon a body, 

 even upon the most transparent, part penetrates, 

 part is reflected, and some part is lost. A dye is 

 a disposition given to the surface of cloth to repel 

 some of the rays of light more than the others ; 

 and the colour will be according to the ray, or the 

 combination of rays, thus cast back and sent into 

 the eye. 



And here it is natural to reflect on the variety 

 and beauty every where bestowed through this 

 property of the beam of light. What a dullness 

 would have pervaded the surface of the earth if 

 there had been only a white light ! The beau- 



