57 
CONSIDERATION OF LIGHT. 
Several years ago we offered a few remarks upon the Philosophy of this beauti- 
ful emanation, which we shall not again repeat; but, as connected with the subject 
of heat, we propose to follow it up, so as to render theory practically useful, either 
by direct inference, or by deduction from observed facts. 
It is probable that we may never attain to a knowledge of the precise nature of 
light, because we cannot determine that of its assured source — the Sun. Still there 
are many phenomena which lead to a shrewd conjecture of its elements, and to 
these we may safely refer. 
There are three distinct series of phenomena, traceable to solar influence, to 
which we invite the attention of the inquiring cultivator ; namely, 1st, those of 
attraction — 2nd, those of temperature — and, 3rd, those of colouration. 
The principle of attraction is manifested in the position assumed by leaves under 
th 3 several angles of sunlight at different hours of the day. Thus, in Erythrina, 
we see the leaflets brought into first the horizontal, and then the upright position, 
at about eight or nine o'clock of the forenoon, and thence to mid-day— -declining 
in proportion as the sun advances to the west. Attraction, whatever be its medium, 
is demonstrative of electric agency ; this, at all events, will not be disputed when 
it is attended with luminous appearances. 
But then, it may be contended, that the phenomena of magnetism and of che- 
mical attraction do not generally, or of necessity, develope light. This is true, but 
as respects magnetism, — which is induced by the electric current, and, therefore, 
dependent upon it ; so much so, as all but to prove that electricity and magnetism 
are one in essence. And as to the latter, when chemical attraction takes place, as 
between acids and alkalies, the combining powers unite, and thus neutralise each 
other. In conformity with these chemical phenomena, light may be considered as 
exerting an invisible attraction upon the points and foliage of vegetables, which 
induces the flow of the sap in an upward direction, and also the lateral courses of 
the fluids through the tissue of the cells, and that of the medullary processes, thus 
producing the laboration and concoction of the proper specific juices of each indi- 
vidual plant. 
There must be a governing agent, — and therefore we repudiate that maudlin 
language which ascribes volition and choice to inanimate structures. 
2. Temperature, its rise and fall, are discerned as measured by our very im- 
perfect instruments. In nine cases of ten, temperature is only a result of excited 
chemical action, of which combustion is one form ; but as referred to the Sun, the 
manifestation of direct heat is generally ascribed to the red rays, while those of 
magnetism are found in the blue and violet. Still the entire solar, or white ray, 
diffuses heat and light, without communicating heat to the transparent medium 
VOL. XII. — no. cxxxv. I 
