of the Solar Spectrum on Vegetable Colours. 115 
good sun sufficing ; but the glairy nature of the juices prevents 
their being evenly tinted, and spoils their beauty *, 
201. The ruddy tint which comes out when the green is 
destroyed by light, is in all probability that which gives the 
whole colour to sere and withered leaves, whether simply dis- 
closed by the destruction of the green which masked it in the 
live state of the leaf, or matured by exposure to light during 
the whole season, either out of the elements of the green co- 
louring matter destroyed, or from the other juices of the vege- 
table. It deserves to be noticed in connexion with this, that 
all the lively vegetable greens have a large portion of red in 
their composition, and are in fact dichromatic. A good ex- 
ample of such a colour is a solution of sap-green, which, used 
as a prism, is seen to transmit both red and green rays, se- 
parating them by a broad interval which increases as the thick- 
ness or density of the solution is increased; the red ultimately 
preponderating, and the green being extinguished. If we 
view a garden or shrubbery through a glass of a pure and 
deep red colour, every shrub, such as the laurel, of a lively 
and brilliant foliage, and especially green grass, will appear 
scarlet. Under such ‘circumstances, a grass-plot, seen in con- 
trast with a gravelled walk, shows as light on darkness, con- 
trary to their habitual order of illumination. So great is the 
quantity of extreme red light reflected by a green sward, as 
actually to appear bright in opposition to clear blue sky seen 
through the same glass in the quarter of the heavens opposed 
to the sun, and that at noon day. The aspect of nature, in- 
deed, when viewed through coloured glasses, is fraught with 
curious and interesting matter of optical remark; but to give 
them their full effect they must not be merely applied to 
one eye for a few moments, as in the use of Claude Lorraine 
glasses. They should be worn as spectacles, both eyes being 
used, all lateral light carefully excluded by black velvet fringes, 
and their use continued till the pupil is fully dilated and the 
eye familiarized with the intensity and tone of the illumina- 
tion. So used, not only are the ordinary relations of all lights 
and colours strangely and amusingly deranged, but contrasts 
arise between colours naturally the most resembling, and re- 
semblances between those naturally the most opposed. We 
become aware of elements in the composition of tints we should 
otherwise never have suspected, and the singularities of idio- 
* Ihave not operated on chlorophyle (the green colouring matter of 
leaves) in a state of purity, owing to the nicety required in its preparation, 
