105 
GARDENING AS A SCIENCE. 
No. V. 
The philosophy of manure — in which term we include every substance that is 
not strictly earthy, but exists in or is superadded to earths — involves some of the 
most mysterious and knotty points of Horticulture. We despair to attempt the 
elucidation of the direct processes by which certain decomposable materials produce 
a specific effect upon individual plants : all that can be accomplished is, to compare 
the components of vegetable structure with those of the manure which is applied as 
food, or stimulus ; and then to cite a few ascertained facts, in order to excite 
further inquiry, while they facilitate the practice of the gardener. 
All modern writers, particularly since Dr. Liebig published his Organic 
Chemistry, have laid considerable stress upon the necessity of determining by the 
action of fire the inorganic salts and earthy substances which exist in individual 
plants ; and they have great reason so to do ; for, in agricultural crops particularly, 
much depends upon the proper application of saline matters. 
We must, if we hope to effect any useful purpose, begin with first principles, 
although at the risk of some repetition. 
Soil consists of earths proper, combined with more or less of decomposable 
matters. A good natural loam is the staple of the field and garden : it comprises 
sandy matter to the extent of more than one half, a large proportion of al limine, 
or the base of clay, a portion of oxide of iron — the source of colour — and a 
varying per-centage of chalk (carbonate of lime). These substances are pure 
earths, in the common acceptation of the word, though strictly speaking, they are 
all of metallic origin. 
o 
Good loam is the foundation of the kitchen-garden ; it is also essential to the 
melon, and every kind of fruit, not excepting the pine-apple. For floriculture in 
pots, however, the parings taken from a pasture or common of loamy earth is 
always preferable, unless we except the fibrous soil, which is obtained by the slow 
decay of couch-grass roots, raked or harrowed from the surface of the very best 
corn-land. This couch-loam, as we term it, varies more or less, according to the 
nature of the land in which the root-stocks grow — proving the fact, that some of 
the earthy ingredients is taken up by the sap-vessels, and deposited in the organs 
of the plant. This loam, incorporated with certain quantities of heath or moor- 
soil, may be rendered suitable to every ornamental plant of the stove or greenhouse, 
with the exception of those hair-rooted tribes which require heath-soil alone. 
The most delicate species of manure (i. e. decomposable matter) is found in 
heath-soil (now erroneously called peat). By analysis of several varieties, it has 
been shown that from 70 to 90 parts in the 100 are white sand, with a faint trace 
of oxide of iron ; the 30 to 10 parts lost being black vegetable remains, destructible 
vol. x. — no. cxiii. p 
