THE SCIENCE OF HORTICULTURE. 
105 
in aerial gases, and as such are invisible : they are " self- restoring," as a modern 
writer justly observed, and are also susceptible of amazingly numerous modifications. 
This is shown in the analyses of that excellent little work, " Fownes' Manual of 
Chemistry." But those constituents also which are termed inorganic, are, or may be 
rendered visible to the eye — and, as in the case of the mineral alkalies, soda, potassa, 
and their neutral salts — are chiefly derivable from the soil. The laboration and 
culture of the ground gradually remove these salts, because vegetables, by each 
taking up its specific supply, deprive the earth of the quantity naturally contained 
in it. Manures restore the organic elements, and some of the salts, but deep 
tillage is the process indicated by nature to bring up, and into activity, the store of 
alkaline and earthy elements that abound in subsoil-loams. "The subsoil of the 
best London market-gardens has been gradually dug up five feet deep to supply the 
waste of mineral matter to the richly-manured soil above." If this last asserted 
fact be true, how greatly do they err, who, in field or garden, are content with 
stirring and turning over the ground, year after year, to the depth of six or eight 
inches. " It will never do," say they, " to bring up a poor and heartless earth, 
that has never been exposed to sun or air ; it would be useless and unproductive for 
years." (!) We advise them to make the attempt, cautiously and by progressive 
degrees. 
For parterre-planting and bedding-out, deep tillage is essential. Every bed 
upon a lawn ought in the first instance to be at least eighteen inches deep of good 
unctuous but not binding loam for the Pelargoniums, Calceolarias, and other strong- 
rooting tribes. Heath-soil with a portion of very light fibrous earth, like that of 
Mitcham Common, is required for the American and hair-rooted shrubs. Leaf- 
mould is admirable for Lobelias. These are general facts familiar to the best 
practical gardeners, who however know little of causes or agencies. But what must 
be insisted on, is the necessity to remove and renew these parterre soils yearly, 
after the two or three first years. Fresh soil, be it of what character it may, is the 
sine qua non. Manure will not answer, it may stimulate, but will not confer that 
magnificence of verdure and colour which are so remarkable in some gardens. One 
of these we have in view, where there was constantly a store of fresh pure loam 
from meadows, kept in heaps exposed to the weather, and this was blended with 
about one- third part of old horse- droppings, taken from the boxes of the mushroom- 
house for the loam-parterre plants. Every bed was dug out in the early spring, 
and refilled with its appropriate earth ; and the effect produced was most splendid. 
Mr. Loudon bore testimony to the justness of this practice, when visiting Taplow 
House, Bucks ; (see Gardeners' 1 Magazine, vol. ix., p. 659.) He wrote — "We were 
particularly struck with the vigorous growth of every description of plant introduced 
into the flower-beds ; and we were informed of the cause, viz., that the gardener 
takes out the soil every year to the depth of two or three feet, and renews it 
entirely. He does not introduce a single bed, or even a single plant, however 
common may be the kind, without this precaution." 
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