128 
TEMPERATURE AND METEOROLOGY. 
solar beam as Light — in other words, that it consists only of that principle or pow 
to which all luminous phenomena are due. Science, however, teaches us that I13 
sunbeam consists of several principles, or is possessed of powers capable of produci 1 
several distinct phenomena.- Vision and colour, calorific action, chemical chanj, 
molecular disturbance, phosphorescent excitation, and electrical phenomena, in thr 
strange duality ; and possibly, many of the more occult forces which so mysterious 
regulate the vital functions of plants and animals, are to be sought for in the sa© 
source.” 
These and similar data are now announced as new; yet, if our memory and mess 
of reference do not deceive us, a then nameless author, commenting upon one f 
the most striking conjectures ever hazarded by such a man as the late Profess r 
Playfair, ventured, in the year 1880, to offer the following suggestions as a Thecz 
of Light : — “ After mature reflection, I am inclined to define solar light as a matei l 
fluid, in its nature the most subtile, penetrating, and energetic — the source of all i 
phenomena of Heat, Electricity, and Magnetism. In all probability, light itself 3 
in its nature subject to decomposition ; it at least exerts an inductive energy, by whi i 
it effects astonishing electro-chemical changes.” Previously he had said, “ When otlr 
facts,” (referring to the theory of coloured rays,) “are carefully investigated, I thi 
it will be found more safe to conclude that the sun’s rays contain a certain princip\, 
by the operation of which colours are produced and developed, than that the whi 
light which comes from the sun, or from any other luminous body, is actually coj- 
posed and made up of seven different kinds of light of different colours, and of suli 
only. Magnetic powers are communicated to needles and small particles of ste , 
by the blue rays. The close analogy which may be traced between electricity ail 
magnetism, might almost warrant the conjecture that light and magnetism, whi 
under certain modifications within the earth’s surface, constitute electric or ej- 
mentary fire, were it not for two considerations : — First, that magnetism is p - 
duced when concentrated electricity passes through space; and then its sph<3 
of action is at right angles to the course of the electricity: thus, a bar of stl 
placed transversely over a wire, conveying an electric shock, becomes a magnet 
Second, that magnetism exerts its energy on iron, nickel, and some other metal 3 
substances.” 
In endeavouring to prove that the sun is the great natural source of all 1 3 
vitalising agencies, the author of The Domestic Gardeners' Manual adduced manyp 
then — hypothetical suggestions, which modern discoveries appear to have substr- 
tiated. Thus the principles of light and heat have been separated; and, therefo, 
if by the use of a pale-green glass, and a plate of alum, Melloni could obstri t 
nearly all the heating rays, while the same media permitted light to pass w:i 
freedom, we should not be surprised if, by the operation of glass surfaces, ta 
(mica), &c., modified and coloured, as casual discoveries may dictate, the solar povf 
will be, eventually, so regulated as greatly to improve the action of glazed roc 
The existence of two principles seems therefore to be established ; what tb 
