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GARDENING AS A SCIENCE. 
No. XI.— FIRE. 
It is a curious circumstance that Fire was by the ancients believed to be an 
element — that is, a simple substance, uncombined with any other portion of matter. 
In the ordinary acceptation of the word, fire, as the product of combustion — that is, 
as the combined development of light and heat — involves a tissue of attractions and 
decompositions of the most intricate character : a few portions of this we propose 
to trace ; but it will be the chief object of tlie article, however strange it may 
appear, to re-establish the elementary character on the basis of pure modern 
chemistry. 
As applicable to the science and practice of Gardening, we shall attend princi- 
pally to the economy of heat in furnaces and flues, but previously shall cite a few 
experimental facts, which the former observations upon the nature and properties 
of the gases may elucidate. After the discovery of oxygen gas by the chemists of 
last century, combustion and the development of flame were ascribed, by Lavoisier 
and his brethren in science, to the combination of oxygen with some inflammable 
base, — all aeriform fluids were deemed " compounds of ponderable bases with light 
and heat" and thus, when a union took place, the light and heat w^ere extricated 
in the form of Jire. The beautiful experiment of the combustion of a coil of iron 
wire in a bell-glass of oxygen, whereby a ' firework ' of extreme brilliancy was 
displayed, not only afl\jrded evidence, but clearly proved, that iro7i thus converted 
to an oxide had acquired a traceable increase of weight. Similar results followed 
the combustion of sulplmr, phosphorus, and carbon : light and heat were developed, 
and the residuary compounds were sulphuric acid, phosphoric acid, and carbonic 
acid gas. The combustion of the diamond in oxygen gas was effected by Lavoisier, 
and has been repeated by other chemists ; it proved that, as the product was a 
volume of carbonic acid, the diamond and pure carbon are chemically the same. In 
this experiment the product of combustion was heavier than the body consumed, 
exactly in proportion to the weight of the oxygen which had disappeared. 
When oxygen and hydrogen gases are mixed together, they remain (in low 
temperatures) unaltered, though each is in an opposite state of electricity. If heat 
be applied, they gradually unite by electric affinity, and watery vapour is produced; 
by flame, or the electric spark, they are instantly exploded with violence ; but if a 
stream of hydrogen gas pass through a fine jet pipe into a bell-glass, standing over 
mercury, filled previously with pure oxygen gas, no explosion will take place, 
provided the hydrogen be ignited the instant before the jet is inserted into the 
vessel of oxygen. The hydrogen will consume gradually, and water be formed 
and trickle down the sides of the bell. 
VOL. IX. NO. CVII. K K 
