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OF GARDENING AS A SCIENCE. 
NO. X.— LIGHT. 
It is not our object to undertake the investigation of this most mysterious 
principle as connected with optics, or the doctrine of colour ; we treat of vegetables and 
the phenomena elicited by the natural agents (of which light is the chief) upon their 
organic structure and developments ; nevertheless, it will not be irrelevant to allude 
to the interesting experiments of Sir Isaac Newton, the late Sir William Herschell, 
and others, so familiarly known to philosophic readers, by which the divisibility or 
decomposition of a ray of white solar light has been proved, and the different heating 
powers possessed by the ray, when so divided, exhibited. 
When a sunbeam is made to pass through a triangular piece of polished glass 
called a prism, an oblong image termed a spectrum is produced, which displays on 
a white screen seven primitive colours, namely, red, orange, yellow, green, blue, 
indigo, violet. The white sunbeam, as every one knows, produces a sensation of 
heat on the hand, though it communicates no degree of warmth whatever to a piece 
of glass ; as, for instance, a burning-glass, through which it passes. But Dr. 
Herschell found that the decomposed ray exhibited very different degrees of heat ; 
thus, “ on applying a delicate thermometer it is seen that the blue ray scarcely 
affects it all ; in the green it rises, and in the red shows an increase of several 
degrees. Assuming the heating power of the violet rays at 16°, that of the green 
is 26°, of the red 55°; but beyond the red ray and the limits of the visible spectrum 
the increase of temperature is still greater.” 
These phenomena, though inconclusive, are yet interesting, and have become 
more so from the recent observations of Dr. Horner of Hull, by whieh it has been 
rendered probable that glass of different prismatic colours may be made available 
to the gardener in effecting different objects : thus, blue glass is supposed to favour 
the first principles of growth, and to promote the germination of seeds, and, by 
inference, the protrusion of roots from cuttings ; while the red, or heating colour, 
and the brilliant illuminating yellow, are more favourable to the processes of 
maturation. Facts however are required to establish and apply the hypothesis : 
in the meantime we feel it right to mention, that during the months of June, July, 
and August, 1841, we kept a number of healthy young pelargoniums in a pit 
facing the north-west, the glazed lights of which were coated on the inside with a 
bluish wash to prevent the drying influence of the afternoon sun. The foliage 
and verdure were much increased, and almost all the plants showed flower-buds ; 
but, strange to say, the figure of these in many instances changed, the trusses flat- 
tened, and the blossoms did not expand, appearing as if absorbed, and finally passed 
into growing shoots. We called the attention of friends to the phenomena, and of 
