into a condition of tillage, at the cost of a large 
supply of manure. No less a quantity of alkalies 
than 12,000 Ibs., in leaves, grain, and straw, was 
removed from every acre of this land during the 
first hundred years of its cultivation; and the 
land became infertile, solely because it was de- 
prived of almost every particle ofalkali which was 
capable of being absorbed by the spongioles of 
plants, and because the fresh portion of alkali 
obtained, in the course of one or two years, by 
further comminution, by the decomposition of 
spontaneous vegetation, and by deposits from the 
atmosphere and from rain water, was not suffi- 
| cient for the requisite support of another crop. 
| Almost all the cultivated land in Hurope—at 
| | least of such as has been for a considerable time 
| in cultivation—is in a similar condition to this 
land of Virginia, and has so totally lost its native 
alkalies as to require continual fresh supplies of 
alkalies, through the processes of fallowing and 
| manuring, in order to its retaining fertility. 
Wheat, whose habits appear so fastidious and 
| capricious to an unpractised or unreflecting ob- 
i server, requires certain phosphates for the for- 
| mation of its grain [see Poospnates and Wuxar], 
and a comparatively large proportion of silicate 
_ of potash for the strength and growth of its culm. 
| Hence, when sown upon sandy or calcareous soils, 
which have not a considerable intermixture of 
| 
| 
clay, and in consequence cannot afford a requisite 
aliment of silicate of potash, the young plants 
will be dwarfed and arrested ; and when sown on 
_ a soil of decayed wood in Great Britain, or even 
_ on any of the rich humous soils of Brazil, the 
| plants, though almost immersed in the seemingly 
nutritious products of vegetable decomposition, 
will so pine foxy the want of mere silicate of potash 
as to be feeble and dwarfish, and speedily to droop 
| and fall—aAll the grasses and all other plants of 
similar structure and habits require some pro- 
| portion of silicate of potash, and therefore thrive 
by irrigation, which both conveys this substance 
to meadows and reduces it to solution in the soil. 
The numerous plants of the equisetum or horse- 
tail type, and also the various kinds of reeds and 
canes, all of which require a large proportion of 
silicate of potash, grow luxuriantly in marshes, 
in ditches, in streamlets, and in such argillaceous 
soils as abound in potash, simply because they 
obtain, in these situations, easy and large sup- 
plies of their favourite alkaline aliment. Most 
deciduous trees, particularly such as carry a large- 
leaved and very profuse foliage, require for their 
leaves from six to ten times more alkali than 
pines or firs; and hence they either do not grow 
at all, or are very dwarfish, on many sandy or 
calcareous lands which are highly favourable to 
the growth of pines or firs,—hence also the finest 
forests of oaks, such as could not be produced on 
_ sandy or calcareous lands, are found on soils of 
gneiss, granite, and mica-slate in Bavaria, of 
clinkstone on the Rhone, of basalt in the Vogels- 
berge, and of clay-slate on the Rhine and in the 
ALKALIES. 
Hifel. “Can we, then, regard it as remarkable,” 
asks Dr. Liebig, “that oak copse should thrive in 
America, on those spots on which forests of pines 
which have grown and collected alkalies for cen- 
turies, have been burnt, and to which the alka- 
lies are thus at once restored; or that the Spar- 
tium scopartum, Hrysimum latifolvum, Blitwm 
capitatum, Senecio viscosus, plants remarkable for 
the quantity of alkalies contained in their ashes, 
should grow with the greatest luxuriance on the 
localities of conflagrations?” An obvious and 
important inference, in regard to the cultivation 
of wheat, of strong culmy grasses, of deciduous 
shrubs and trees, and of any other plants which 
require large supplies of alkaline matter, is that, 
when the land intended for them has been de- 
prived by cultivation of its native soluble alka- 
lies, it must be specially prepared, or brought 
into a condition of fitness, by one or more of the 
appliances for impregnating it with fresh alka- 
lies, either the abandonment of it to a state of 
nature, or the growth upon it of crops which do | 
not require alkalies, or the enriching of it with 
such manures as contain a large proportion of 
alkaline ingredients. 
One of the prime offices performed by water in 
connexion with vegetation, is the reduction of 
the alkalies to such a state of solution as to ren- 
der them absorbable by the spongioles of plants. 
During spring and the early part of summer, 
while soils are in a moist condition, a greater 
quantity of alkaline bases and salts enters the 
organism of land-plants, than during the middle 
and later parts of summer, when soils are com- 
paratively dry or arid. The descent of rain upon 
a soil is the introduction of certain necessary 
alkaline matter in a state of readiness for use 
by both soil and plant, and the action of water 
within the soil is the preparation of other neces- 
sary alkaline matter in combination with accom- 
panying aliments for the vegetable organism. 
The necessity of rain for these purposes is so spe- 
cially great at certain stages of the growth of 
plants, that, in many districts, the stuntedness 
or the luxuriance, the strength or the weakness, 
the opulence or the poverty, of a whole season’s 
crop of corn may depend on the presence or ab- 
° 5 | 
sence, the copiousness or the paucity, of one day’s | 
rain, or even of a single shower. In dry seasons, 
the lower leaves of annual plants in summer, the 
lower leaves of herbaceous perennial plants at a 
later period in summer or early in autumn, and 
the lower leaves of deciduous perennial short- 
rooted plants just before autumnal maturity, lose 
their vitality, become yellow, shrink, and fall. 
These leaves were the earliest developed; they 
received alkaline juices from the ascending sap 
of the plant, and carbonic acid and ammonia 
from the surface action of the atmosphere; they 
elaborated these ingredients into the constituents 
of new leaves, buds, and twigs; and, when a con- 
tinuance of drought occasions a scantiness or a 
cessation in the supply of alkaline matter through 
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