108 
SHADING. 
eminently useful science—chemistry. Light, as it is. commonly 
known, such as pervades our horizon in the daytime, is composed 
of three colours, called the primitive rays, they are yellow, red, 
and blue; these completely blended form white, and by their 
union we enjoy a colourless or white medium, through which 
objects are clearly visible in their own peculiar tones ; each of 
these prismatic tints, however, possess separate and distinct 
actions, which are manifested upon vegetation more quickly than 
upon the animal frame, because of the predisposing union of 
those tints which form the colour distinguishing that portion of 
creation ; the yellow ray conveys light alone, the red is the 
burning ray, and the blue is distinguished by chemical action : 
acting in the most beneficial proportion, the last may be regarded 
as the life-giving principle which the other two nurture and 
mature ; but their proportions vary, and thus it is that at certain 
seasons the predominance of one or other, causes the several 
phases in the existence of vegetation known as the growth and 
ripening of the wood; the red ray is most powerful in summer 
because transmitted to us through a clearer medium than at other 
times, and our exotic flora just awakened from the dormancy of 
winter, has not yet had time to develope its accessions, because 
of the shortness or inert character of our seasons, as compared 
with those of its native climes, and being thus prematurely 
subject to the ripening principle, suffers in proportion to its 
intensity. The idea of separating or condensing one or other of 
these rays to suit the exigencies of different classes of plants in 
their several stages towards maturity has for some time engaged 
the attention of scientific cultivators, and the possibility of the 
thing being established by their researches, it has become only 
necessary to determine how much of either will be most beneficial, 
or rather what combination will be required for furthering the 
object in view r . For plants still in a growing state, the exclusion 
of the red ray seems to be most necessary, as it is to its influence 
that scorching may be plainly traced ; but then we have the period 
of maturity to provide for, and without securing that to the 
fullest degree, it is well known all previous labour is void and 
waste ; to provide a permanent medium through which the plants 
should only receive such a light as is most conducive to growth, 
would be leaving the work but half done, and for this reason we 
