250 
GARDENING AS A SCIENCE. 
Chlorine gae, if united with hydrogen in equal volumes, will combine chemically 
without heat, and form muriatic acid ; but if the mixed gases be exposed only to the 
direct solar ray, an explosion will frequently ensue. A jet of hydrogen gas, first 
inflamed and admitted into a glass vessel containing chlorine gas, will continue to 
burn till gradually the yellow colour of the latter will vanish, and muriatic acid 
gas be produced 
Thus, light and intense heat are evolved by the chemical union of two elastic 
fluids ; and the question, therefore, most naturally occurs — what is their source 
and origin ? 
An apparatus, consisting of copper and zinc, or of platinum and zinc 
plates arranged in alternate order, constitutes what is termed a voltaic or 
galvanic battery. This instrument, excited by a diluted acid, composed of ninety- 
five parts of water and five parts of mixed nitric and sulphuric acids, will induce 
phenomena of light and heat of a grandeur and intensity altogether startling. Thus, 
in the experiments with a large instrument like the celebrated battery of Mr. Chil- 
dren, — " "When gold, silver, zinc, and copper leaf were interposed between the 
poles, they were ignited and burned, and fine wires heated red or white hot 
according to their lengths and diameters. With an iron wire, the combustion is 
particularly brilliant. The extreme intensity of the heat in the arc of flame, pro- 
duced between charcoal points, was made evident by exposing to it substances of 
difficult fusibility ; these melted, and others, infusible by ordinary methods, w T ere 
thus liquified." 
Now these luminous and powerful effects are produced by the attractions 
exerted between metallic surfaces in cells containing water slightly acidulated, 
throughout which there is not the slightest trace of visible light. How manifest, 
then, it is, that the fire so developed must lie hidden in the materials employed 
till it be revealed and brought into play by chemical action! and how stupendous 
must be the volume of this ethereal essence, when an apparatus of almost infinitely 
less pow T er was proved by the experiments of Faraday to generate in the space of 
three minutes a stream of electricity equal in volume to that of a powerful flash of 
lightning ! If, then, all natural and all known substances be replete with 
electricity, (for by this term it is yet customary to designate ethereal fire) ; if every 
act of percussion or friction disturb, and to a greater or less extent reveal it ; if the 
Tery air w T e breathe emit a flash of light when suddenly compressed, and every 
grain of common water be replete with it ; then we may safely infer the elementary 
nature of fire, since its origin must be the sun, and its depositary the globe and its 
waters. 
The combustion of fuel which, practically, is of the most immediate importance 
to the gardener, is a process of great complexity. The prime agent, or exciter, is 
doubtless simple, but the elements upon which it acts are multifarious. Thus 
wood consists, — so far as analysis can decide, — of solid oxygen, hydrogen, and 
carbon. We say consists, because the results of the most refined experiments 
