380 Dr. Wollaston's Method of examining, See. 
By candle-light, a different set of appearances may be dis- 
tinguished. When a very narrow line of the blue light at the 
lower part of the flame is examined alone, in the same manner, 
through a prism, the spectrum, instead of appearing a series of 
lights of different hues contiguous, may be seen divided into 5 
images, at a distance from each other. The 1st is broad red, 
terminated by a bright line of yellow; the 2d and 3d are both 
green ; the 4th and 3th are blue, the last of which appears to 
correspond with the division of blue and violet in the solar 
spectrum, or the line D of Fig. 3. 
When the object viewed is a blue line of electric light, I have 
found the spectrum to be also separated into several images; 
but the phenomena are somewhat different from the preceding. 
It is, however, needless to describe minutely, appearances which 
vary according to the brilliancy of the light, and which I cannot 
undertake to explain. 
to the common prismatic spectrum, it is blackened more in the violet than in any other 
kind of light. (§ 66.) In repeating this experiment, I found that the blackness ex- 
tended not only through the space occupied by the violet, but to an equal degree, and 
to about an equal distance, beyond the visible spectrum ; and that, by narrowing the 
pencil of light received on the prism, the discoloration may be made to fall almost 
entirely beyond the violet. 
It would appear therefore, that this and other effects usually attributed to light, are 
not in fact owing to any of the rays usually perceived, but to invis.ble rays that 
accompany them ; and that, if we include two kinds that are invisible, we may distin- 
guish, upon the whole, six species of rays into which a sun-beam is divisible by- 
refraction. 
