34 SIS ISAAC NEWTON. 



nor on the tops of the highest mountains, it might 

 extend to the moon, about which he had been study- 

 ing, and retain her in her orbit. If to the moon, 

 why not to the planets ? 



The tree from which the apple fell was so much 

 decayed in 1820, that it was cut down, but the 

 wood was carefully preserved by Mr. Tumor of 

 Stoke Eocheford. 



In the beginning of the following year, 1666, 

 when Newton was twenty-four, he purchased a 

 prism, in order to make some experiments on Des- 

 cartes' theory of colors. He made a hole in his 

 window shutter, darkened the room, and admitted 

 a ray of the sunlight. On the opposite wall he 

 saw the solar or prismatic spectrum, an elongated 

 image of the sun, about five times as long as it was 

 brpad, and consisting of seven different colors ; red, 

 orange, yellow, green, blue, indigo, and violet. 

 White light was thus discovered to be of a com- 

 pound nature; a mixture of all the oolors. He 

 said, "AVhiteness is the usual color of light; for 

 light is a confused aggregate of rays endued with 

 all sorts of colors, as they are promiscuously darted 

 from the various parts of luminous bodies." If any 

 one color predominates, the light will incline to 

 that color, as the yellow flame of a candle. Here- 

 tofore, there had been all sorts of conjectures 

 about the nature and origin of colors. Descartes 

 believed them to be a modification of light, depend- 

 ing on the direct or rotary motion of its particles. 

 But Newton showed by many experiments that 



