A new Theory of Light. 419 
gun-beam admitted into a darkened room, and observed 
that it reflected a far greater light than a paper of any other 
colour, a considerable part of the room being enlightened 
by it, Further to show that white bodies reflect the rays 
outwards, Mr. Boyle adds, that common burning-glasses 
will not of a long time burn or discoleur white paper. 
When he was a boy, he says, he took great pleasure in 
making experiments with these glasses: he was much sur- 
prised at this remarkable circumstance, and it set him very 
early upon guessing at the nature of whiteness, especially 
as he observed that the image of the sun was not so well 
defined upon white paper as upon a black one; and as, 
when he put ink upon the paper, the moisture would be 
quickly dried up, and the paper which he could not burn 
before would presently take fire. He also found that, by 
exposing his hand to the sun, with a thin black glove upon 
it, it would be suddenly and more considerably heated 
than if he held his naked hand to the rays, or put on a 
glove of thin white leather. To prove that black is_the re- 
verse of white, with respect to its property of reflecting the 
rays of the sun, Mr. Boyle procured a large piece of 
black marble ; and having got it ground into the form of a 
large spherical concave speculum, he found that the image 
of the sun reflected from it was far from offending or daz- 
zling his eyes, as it would have done from another specu- 
Jum; and though this was larger, he could not in a long 
time set a piece of wood-on fire with it, though a far less 
speculum of the same form, and of a more reflecting sub- 
stance, would presently have made it flame. To satisfy 
himself still further with respect to this subject; he took a 
broad and large tile, and having made one half of its sur- 
face white, and the other black, he exposed it to the sum- 
mer sun; and having let it tie there some time, he found 
that while the white part remained cool, the part that was 
black was grown very hot. For his further satisfaction, he 
sometimes:left part of the tile of its native red, and after 
exposing the whole to the sun, observed that this part grew 
hotter than the white, but was not so hot asthe black part*. 
Mr. Boyle not being aware of the fact lately ascertained 
by the experiments of Herschel and other scientific men, 
that luminous and calorific rays are separate and distinct, 
and as all his reasoning depends on the identity of heat and 
light; we must look on his facts and experiments ag in- 
® Boyle’s Works, p. 6. 
Dade conclusive, 
