of the Solar Spectrum on Vegetable Colours. 109 
meric paper was fixed on the Chryseis paper, so that its edge 
should bisect the spectrum longitudinally from end to end, the 
preceding half of the sun’s lengthened image being received 
on the one paper, and the following half on the other. The 
papers thus arranged were so similar as hardly to be distin- 
guished when simply laid in sunshine, but when illuminated 
by the spectrum, as above described, the half of it on the tur- 
meric side was plainly seen to extend far beyond the other, as 
represented in fig. 6. 
189. Hitherto I have met with only one other coloured 
paper which possesses a similar character in respect of its 
reflective power, and that by no means in so high a degree. 
To prepare it, the alcoholic tincture of the dark purple dahlia 
must be alkalized by carbonate of soda. The mixture is vivid 
green, which is also, at first, the colour of‘paper stained with 
it. But this colour changes in about twenty-four hours to a 
fine yellow, a little inclining to orange, after which it is re- 
markably permanent, and very little sensible to photographic 
impression. On this, as on the turmeric paper, the prolonga- 
tion of the spectrum appears as a pale yellow streak. And 
if such, rather than lavender or dove-colour, should be the 
true colorific character of these rays, we might almost be led 
to believe (from the evident reappearance of redness min- 
gled with blue in the violet rays) in a repetition of the primary 
tints in their order, beyond the Newtonian spectrum, and that 
if by any concentration rays still further advanced in the “ che- 
mical” spectrum could be made to affect the eye with a sense 
of light and colour, that colour would be green, blue, &c., ac- 
cording to the augmented refrangibility. 
190. Cases of negative Photographic Action on Vegetable 
Tints.—Among. a collection of plants which I made at the 
Cape of Good Hope, and have succeeded in rearing in Eng- 
land, occurred three species of a genus allied to Antheri- 
cum, with brilliant yeliow flowers in lengthened spikes, and 
highly characteristic furred anthers, to which I am not botanist 
enough to assert the correct application of the name Bulbine, 
assigned to them by a friend in Cape Town. Of these three 
species, two (Bulbine bisulcata and... . .) yield from the green 
epidermis of their leaves and flower-stalks a bright yellow 
juice which darkens rapidly on exposure to light, changing 
at the same time toa ruddy brown. Exposed to the spec- 
trum, the less refrangible rays are found inoperative, either 
in inducing the change of tint, or in preserving that por- 
tion of the paper on which they fall from the influence of 
dispersed light. The negative action commences at the fidu- 
cial yellow, is very feeble as far as + 10, where it begins to 
