262 A. M. Mayer—History of Young's 
say, he omits from this account of his theory all mention of the 
Aaa explanation of it which he gave in the Bakerian 
ecture of 1801. The following extracts from the Natural 
Philosophy give all that it contains on the theory of colors, 
he italics are our own. 
“Tt has generally been supposed, since the time of Newton, 
that when the rays of light are separated as completely as pos- 
sible by means of refraction, they exhibit seven varieties of 
colour, related to each other with respect to the extent that they 
occupy, in ratios nearly analagous to those of the ascending 
scale of the minor mode in music. The observations were, 
however, imperfect, and the analogy was wholly imaginary. 
Dr. Wollaston has determined the division of the colored image 
light, he produces a more effectual separation of the colors than 
of four colors only, red, green, blue and violet, which occupy spaces 
in the proportion of 16, 23, 86 and 25, respectively, making to- 
gether 100 for the whole length ; the red being nearly one-sixth, 
the green and the violet each about one-fourth, and the blue 
more than one-third of the length. The colors differ scarcely at 
all in quality within their respective limits, but they vary in bright- 
ness ; the greatest intensity of light being in that part of the 
green which is nearest the red. A narrow line of yellow is gen- 
erally visible at the limit of the red and green, but its breadth 
scarcely exceeds that of the aperture by which the light is ad- 
mitted, and Dr. Wollaston attributes it to the mixture of the red 
with the green light. There are also several dark lines crossing 
the spectrum within the blue portion and in its neighborb 
zy of the deviation of the red rays; by a prism of flint glass 
5. Fig. 3.* 
To: Oo. : 
Fig. 8. “The spectrum produced by looking through a prism 
at a narrow line of light. 
* These figures, 3 and 4, are copied of the exact size of those given by Young 
in the plates appended to his Natural Philosophy. The descriptions under the 
$ are those given by Young. The colors in Young’s figures we have 
inline : 
ee a ae ee ee ay ee ee ee 
