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GARDENING AS A SCIENCE. 
No. VI. — MANURES AND THE FIXATION OF NITROGEN. 
In the article No. V., a few facts were adduced concerning the effects observ- 
able on the application of various decomposable substances, which we term Manures. 
The subject is by no means exhausted ; — so far from it, that it appears we really 
know but very little of leading philosophical principles. In every quarter we not 
only perceive that attention has been directed to the preparation and advertisement 
of new manures as a source of trading emolument, but the press teems with the 
conjectural theories of numerous writers whose experience scarcely, perhaps, 
amounts to the observation of a few horticultural phenomena. 
Still, inquiry is alive and active, and therefore we may be assured that science 
will extend, and practical improvements follow. 
We shall shortly have occasion to allude to the authority of Liebig, who has 
pioneered the way to all the modern theories that have been ushered to light since 
the publication of his Organic Chemistry, but previously must recur to that great 
principle of manuring which instructs us that every product of vegetable organized 
life must be placed either by nature or art within the sphere of the plant's attrac- 
tion ; and therefore if we propose to obtain luxuriant vegetables, perfect in all their 
parts, we must apply manures which contain, in one form or other, all the elements 
of those vegetables. Now, leaves of all descriptions, as being parts of plants, 
must of necessity comprise the required elements, and as such we uphold them to 
be the best and safest of all manures. 
No one can take up a periodical of agriculture or gardening, without acquiring 
some ideas of what are the received opinions of the day concerning vegetable 
structure and function. He will see that most plants and their products develop, 
when decomposed by chemical processes, the elements which we call oxygen, 
hydrogen, carbon ; and that some others yield a quantity of the gas called nitrogen. 
The leaves of trees in a state of decay, produce, in every instance, the three first- 
named elements, while those of the cabbage tribe, and similar strong- smelling 
herbaceous plants, afford evidence of the presence of much nitrogen. Here then we 
find all the components of organic structure, and therefore are justified in recom- 
mending half-decomposed leaves upon philosophical principles — that is to say, from 
the induction of facts. 
We are aware that they who advocate the super-excellence of stable manure 
will exclaim against the use of leaves ; we must therefore appeal to experience. 
In melon-growing, it is common to recommend pure, virgin, strong loam as a staple, 
and this also to be trodden down to a solid bed of almost impenetrable texture. 
Melons, doubtless, have been produced of fine quality under such treatment, but 
we are equally sure that they are grown with undeviating success by a process 
vol. x. — no. cxiv. s 
