ON THE CHEMICAL ACTION OF THE SOLAR RADIATIONS. 263 
to *80; the other rays continue unchanged, exhibiting a tolerable degree of 
intensity. When concentrated by a lens the violet ray is seen to suffer yet 
further extinction relatively to the other rays. 
(6) 18. Meprum YELLOow, believed to be Charcoal.—The red ray exhibits 
more crimson from the introduction of blue ; orange and yellow well-defined ; 
green ray somewhat shortened, but exhibiting considerable intensity, and well- 
defined. The blue ray reduced to a small band, and the rays beyond are 
only indicated by a pale stream of light, neutral in colour. 
(7) 14. Brown yeLtow, by Carbon, fig. 2—Red Fig. 2. Fig. 3. 
and yellow rays are considerably reduced ; the green is 
well-defined, shading off into blue, of which a faint 
portion alone remains, the space beyond appearing ra- 
ther a lavender colour than violet. 
(8) 17. Derr yELLow, by Iron, fig. 3.—This spec- 
trum consists of four well-defined and nearly equal 
circles, or rather oval spaces. No blue can be de- 
tected in the spectral image; the green rays occupying Uy ; i | re 
the place of the blue; the yellow rays considerably ex- ———% a’ 
tended ; the red rays are well-defined, but on the upper 
edge a band of scarlet or deep orange is detected when the eye has become 
accustomed to the light. The violet has more red than usual in the rays; 
and at the upper edge, after long gazing, is seen a faint line of neutral gray, 
the lavender ray of Herschel. 
(9) 45. A vELLow cass, having a peculiar pink hue—Does not pro- 
duce any change on the coloured rays of the spectrum; it appears to pro- 
long the yellow by reducing the upper edge of the orange aud the lower 
edge of the green. 
(10) 113. VERY DARK SMOKY BROwN.—AIl blue flowers appear of a 
deep red brown. Purple and claret-coloured flowers lose all their blue, and 
appear red. The red, orange and green rays only are visible through this 
glass, and the illuminating power of those is very considerably diminished. 
(11) 114. A LIGHTER BROWN THAN 113.—A very much more decided 
action on natural colours than 113. An examination of the spectrum shows 
that the red rays are slightly shortened; the orange and yellow rays blend, 
the yellow coming out in much purity ; the green rays are well-defined, but 
cut off somewhat sharply at the more refrangible end. Beyond these, by 
accustoming the eye to the light, a faint trace of blue becomes gradually 
apparent. 



(B.) Series of Red Gilasses. 
(12) 50. Pink GLass(not very clear), fig. 4.—The illuminating 
powers of all the rays considerably reduced. The violet rays are 
lengthened and the indigo lost; the blue also considerably short- 
ened. The influence of this glass is of a very marked character in 
separating the rays from each other, every ray visible being well 
marked out. The orange rays are only made out after long exa- 
mination as a line of inconsiderable width edging the red rays. g 
By using two thicknesses of this glass, and a spectrum concen- y 
trated by a lens, the orange rays are brought out as a well-marked tb ra’ 
band, edged by two black lines. 
(13) 13. VioLer GLass, fig. 5.—Ist. Rays passed through the glass 
to the prism. The spectrum appears divided into two distinct parts. The 
illuminating power of all the rays lessened. In the lower section (1, a), 
red, orange and green are visible; blue and violet occupying the space 6. If 
Fig. 4. 

