70 POLARIZED LIGHT AND ITS APPLICATION TO THE MICROSCOPE. 
CHAPTER IV. 
POLARIZED LIGHT AND ITS APPLICATION TO THE MICRO- 
SCOPE. 
9-1. Tlicories of Light. Formerly light was supposed to 
consist of material particles, or corpuscles, projected in all 
directions from luminous bodies. This theory is generally 
ascribed to Sir Isaac I7ewton, but I7ewton really held that in 
addition to the projection of luminous corpuscles, each moving I 
particle in its flight produced vibrations in the surroundins 
ether, similar to the waves produced by a stone fallingdnto the/ 
w’ater. I 
Huyghens maintained, in opposition to Newton, that lighf 
consisted solely in vibrations of an etherial medium, originated 
by luminous bodies, without the onward progress of any sub- 
stance whatever. With some modifications, the theory of 
Huyghens is generally adopted by men of science at the 
present time, though the honor of developing, and, to a great 
extent, demonstrating, the undulatory theory of lights is due to 
Dr. Young, Sir David Brewster, and other modern philosophers. 
95. Double Refraction and Polarized Light have con- 
stituted the great battle ground of science in advancing th^ 
claims of rival theories of light. Some principal facts in r^ 
gard to the polarization of light by the double refraction df 
Iceland spar, were known to Newton and Huyghens, but tpe 
development of the Science of Polarized Lights dates from me 
early part of the present century. 
In 1808, the Royal Institute of France offered a prize for/the 
J. & W. GRUNOW k GO’S ILLUSTRATED 
