56 
OF GARDENING AS A SCIENCE. 
vegetables contain organic acids generally combined with the inorganic bases, or 
metallic oxides ; for these metallic oxides exist in every plant, and may be detected 
in its ashes after incineration. Nitrogen is an element of vegetable albumen and 
gluten ; it is a centient of the acids, and of what are termed the ' indifferent 
substances ' of plants, as well as of those peculiar vegetable compounds whicii 
possess all the properties of metallic oxides, and are known as ' organic bases.' It 
follows from the facts thus far detailed, that the development of a plant requires 
the presence — first, of substances containing carbon, and nitrogen, and capable of 
yielding these elements to the growing organism : Secondly, of water and its 
elements ; and lastly, of a soil to furnish the inorganic matters which are likewise 
essential to vegetable life." 
In this quotation, given at length, we recognise the leading principles of 
vegetable culture : the main facts are not new, neither are they doubted by any 
philosophic observer ; but they have been misunderstood, and misapplied, as we 
shall discover in due time. It has been, and will be, our desire to avoid all dark 
and mysterious terms — terms exclusively professional j but as those who allude to 
science must, to a certain extent, employ its phraseology, we have now cited terras 
which are in the mouth of numbers, and are to be heard every day, though, in point 
of fact, they are little understood, and still less appreciated. 
In order to convey some idea of their express meaning, we shall say a few words 
upon each of the vegetable constituents above-noticed, though not strictly in the 
order in which they occur. 
1. Carbon. This word implies coal, or charcoal, and is most readily interpreted 
by referring to the charcoal of wood — that substance which remains after the slow 
combustion of w^ood, particularly in those close iron retorts which are employed in 
the manufacture of pyroligneous acid. Its quantity is very great, though various, 
and may in the gross be stated as approaching to something under half the entire 
weight of the dried wood. Carbon also enters largely into the composition of all 
vegetable products. 
2. Oxygen, as far as we know it, is an air or gas : — it is that vital principle of 
the atmosphere which sustains respiration, light, and flame ; it exists invariably in 
the proportion of 21 parts of every 100 parts of air by measure, and that at every 
season. 
3. Nitrogen is that inert, inactive portion of air which remains after the 
removal of the oxygen ; it constitutes the bulk of atmospheric air, in volume 
amounting to 79 parts of every 100 parts : it is not respirable, cannot support 
flame, and is fatal to life ; its presence may be easily shown by placing a lighted 
taper under a large bell-glass, the rim of which is immersed in water to prevent the 
access of air. As the taper burns the water will rise within the bell-glass, and w^hen 
the flame is extinguished, (which it soon will be,) the fluid will leave its mark at a 
place w^hich will prove that about one-sixth of the air has been removed : this will 
be an approximation to the truth, though the experiment admits of much inaccuracy. 
