203 
ON THE AGENCY OF SOLAR LIGHT. 
The article upon the " Influence of Climate" — if it be perused with the interest 
which the subject, and the way in which it is treated, merit, will make a great 
impression upon the physiological gardener. We hope the writer will pursue 
the inquiry, and adduce many facts which will assist the practice of those amateurs 
who have few opportunities to obtain correct information concerning the native 
habitats, climes, and situation, as respects soil and exposure, of those plants which 
are the objects of their solicitude. 
It is allowed that, under any circumstances, however favourable they may be, 
exotics, introduced to our greenhouses and stoves, are and must be, treated 
unnaturally. Were we able to apply the great natural agents — air, moisture, 
and temperature, in a manner and degree closely approaching to those of nature, 
certain it is that the intervention of a screen of glass would at once change the 
operation of solar light ; for the rays, in their passage through that chemical 
medium, become more or less refracted, and decomposed. Now, if allowance be 
not made for the alterations so produced, there will be perpetual miscalculations ; 
of this the following fact — of too frequent occurrence — will afford some degree of 
proof. 
A fig-tree in a large pot, which had set two dozens, or more, of fruit, in a stove, 
remained healthy, and clothed with a richly verdant foliage ; but, owing to the 
high temperature of the house, it lost every fig in succession, when about half swelled. 
When it was found that the figs could not be produced ripe in that situation, 
the tree was removed ; and, the weather being fine and warm, it was placed in 
the open air, and — without due reflection — in a sunny exposure. In the house 
the rays had fallen upon the tree, which had no protecting screen, other than that 
of the glass ; but the angle of the lights was not above 26 degrees, according to 
the French method of dividing the quadrant, or of 64 degrees according to that 
practised in England (see this subject elucidated at p. 257-8, vol. ii.) ; consequently 
the light was considerably broken, and its power much qualified. The fig-tree had 
not been exposed during many hours, ere every leaf was paralysed and drooped ; 
in two or three days the verdure was changed to a sickly yellow, and the entire 
foliage perished ! 
Greenhouse plants placed abroad in their summer quarters have to pass through 
this trying ordeal ; there is not one of them but suffers more or less ; all are tor- 
pified ; and, unless they be well shaded on their first exposure, lose much of their 
beauty, and become anything but objects of attraction during the best of the 
summer months. 
From these considerations, the remarks on light — at p. 112 — must be received 
with some qualification, and that upon the following ground : — first — the solar 
rays passing through glass, lose much of tlieir direct power; second — a great 
