264 REPORT—1852. 
the spectrum is concentrated by a lens and then 
examined through this glass, the images appear 
as in (2a), joined by a thin neck of a neutral 
tint. Few spectra are more beautiful than this 
when all the extraneous light is cut off, each 
colour being so very distinctly and clearly made 
out, the lower illumination enabling the eye to 
examine it without weariness or confusion. 
(14) 12. Rep crass (Gold), fig. 6.— The 
spectrum becomes an oval spot of intense red- 
ness with a prolongation of the same colour; the 
red oval comprehending all the rays from the upperend fig. 6. Fig. 7. 
of yellow to the end of ordinary red, and the prolongation ds a 

flowers observed through it appear far more red than 
under ordinary circumstances. The spectrum separated 
into two long ovals, one, 6, being violet, and the other, 
e, exhibiting the red and green rays only, the spectrum 
being very considerably shortened at the least refran- 
gible end. i) ee aa 
(16) 119. VioLert.—This glass obstructs but a very 
small quantity of light, and its action upon the spectrum is not very decided. 
The red rays are seen in great beauty and purity extending over the space 
covered by the orange rays; the yellow is very pure, but the green is some- 
what diminished in intensity, and also in length. The violet rays are prolonged 
into the blue, thus shortening the latter, which are however very brilliant. 
(17) 48. A deep and not very pure violet.—The red rays are slightly 
shortened at the lower end, but they appear extended as they in- ,, 8 
crease in refrangibility, so that the orange and yellow rays present a 
a long band of a pale orange tint uniform throughout. The blue -~ 
rays are sharply cut off from the violet, the interposing indigo being 
nearly black; the violet rays being themselves exceedingly beau- 
tiful and clear. 
(18) 104. Lirac GLass (Manganese), fig. 8.—Reds of flowers 
seen in strong contrast with the leaves, which appear darker from 
the loss of their yellow. The yellow rays of the spectrum are nearly 
obliterated ; red shortened; green is gradually lost in black sha- 
dow, and all the other rays blended in an intense oval patch of blue. 
(C.) Series of Green Glasses. 
(19) 36. ApPLE.GREEN GLASS.—The red rays are shortened one-half, 
the yellow extends into the orange, and is sharply cut off without any blend- 
ing at the edge of the red; on the more refrangible side the green 
encroaches considerably on the yellow, and upwards into the blue; Fig. 9. 
the violet by extending into the blue obliterates the indigo. 
(20) 33. INTENSE GREEN, fig. 9.—All the rays below the orange 
are cut off; the yellow and green form one tint of pale pea-green. 
The blue rays are very light in colour, losing but little of their 
illuminating power, and these are fringed with a deep band of 
indigo ; no violet rays apparent. 
(21) 34. Green. Copper of great brilliancy, tig. 10.—The red 
below the orange cut off; does not shorten the violet end, but pro- 
duces a great extension of the blue ; the green rays encroach consi- 
g 
7 

extends to the edge of the blue. b 
(15) 117. VIOLET-COLOURED GLAss, fig. 7.—Blue §: 
@ 
a 
a 



