182 Prof. O. N. Rood on a New Theory of Light, 
Art. XVI.—On a new Theory of Light, proposed by John Smith, 
M.A.; by O@DEN N. Roop, Professor of Chemistry in Troy 
University. 
certain fraction of a second; it is succeeded by shadow or dark- 
ness, which lasts also during a certain short interval of time, 
when the operation is repeated anew, &c ; 
This pulsation of light and shade the author effects in a variety 
black spiral figures painted on them, when set 1. 
A blackened disc nine inches in 
diameter, was cut with four slits of the shape 
Seen in the wood cut; the width of the slits 
at the circumference was 7s Of an inch; the 
disc was made to rotate before a bright cloud. 
* Pogg. Ann. vol. xly, p. 227. 
