366 
and the importance of increasing that power by 
pulverizing the soil, is not nearly so well under- 
stood as is desirable, although the farmer has 
the means of convincing himself of the fact by 
the most simple experiments. It is, in truth, an 
almost unfailing test of the comparative value 
of soils, as was long since observed by Sir H. 
Davy,—a conclusion in which I have often had 
occasion to agree. ‘The power of the soil,’ says 
this great chemist, ‘to absorb water by cohesive 
attraction, depends, in a great measure, upon 
the state of division of its parts; the more 
| divided they are, the greater is their absorbent 
powers. The power of soils to absorb moisture 
from air, is much connected with fertility ; when 
this power is great, the plant is supplied with 
moisture in dry seasons, and the effect of eva- 
poration in the day is counteracted by the ab- 
sorption of aqueous vapour from the atmosphere 
by the interior parts of the soil during the day, 
and by both the exterior and interior during 
the night. The stiff clays, approaching to pipe- 
clays in their nature, which take up the greatest 
quantity of water, when it is poured upon them 
in a fluid form, are not the soils which absorb 
most moisture from the atmosphere in dry wea- 
ther; they cake, and present only a small surface 
to the air, and the vegetation on them is gen- 
erally burnt up almost as readily as on sands. 
The soils that are most efficient in supplying the 
plant with water by atmospheric absorpticn, are 
those in which there is a due mixture of sand 
finely divided, clay and carbonate of lime, with 
some animal or vegetable matter, and which are 
so loose and light as to be freely permeable to 
the atmosphere. With respect to this quality, 
carbonate of lime and animal and vegetable mat- 
ter are of great use in soils,—they give absorbent 
power to the soil, without giving it likewise 
tenacity; sand, which also destroys tenacity, on 
the contrary gives it little absorbent power. I 
have compared the absorbent powers of many 
soils with respect to atmospheric moisture, and 
I have always found it greatest in the most fer- 
tile soils, so that it affords one method of judging 
of the productiveness of land. One thousand 
parts of a celebrated soil from Ormiston, in Hast 
Lothian, which contained more than half its 
weight of finely divided matter, of which eleven 
parts were carbonate of lime, and nine parts of 
vegetable matter, when dried at a temperature 
of 212°, gained in an hour by exposure to air 
saturated with moisture at a temperature of 62°, 
eighteen parts; 1,000 parts of a very fertile soil 
from the banks of the river Parret, in Somerset- 
shire, under the same circumstances, gained six- 
teen parts; 1,000 parts of a soil from Mersea, in 
Essex, worth 45s. per acre, gained thirteen parts ; 
1,000 parts of a fine sand from Essex, worth 28s. 
an acre, gained eleven parts; 1,000 of a coarse 
sand, worth 15s. per acre, gained only eight 
parts; 1,000 of the soil of Bagshot Heath gained 
SUBSO1L-PLOUGHING. 
atmospheric moisture is not only an inherent pro- 
perty in all fertile soils, and a property which is 
increased by their pulverization, but it exists in 
a still more remarkable degree in the commonly 
employed manures of the cultivator, and that, 
too, nearly proportionate to their commonly as- 
signed value. The following are the results of 
my own experiments:—One thousand parts of 
horse-dung, dried at a temperature of 100°, ab- 
sorbed, by exposure for three hours to air satu- 
rated with moisture at 62°, 145 parts; 1,000 
parts of cow-dung, under the same circumstances, 
absorbed 130 parts; 1,000 parts of pig-dung ab- 
sorbed 120 parts; 1,000 parts of sheep-dung ab- 
sorbed 81 parts; 1,000 parts of pigeons’ dung 
absorbed 50 parts; 1,000 parts of a rich soil 
worth two guineas per acre, absorbed 15 parts. 
This attractive power of the earths, and of ma- 
nure, from the moisture of the atmosphere, is 
one of the most important facts to be kept in 
mind by the farmer, when he is considering the 
pulverizing and deepening his soils, It is alsoa 
property which all plants possess in a certain 
measure, but some in such a perfect degree as 
to depend entirely upon it for all the moisture 
they need. Thus, the aérial epidendron, Hpzden- 
dron flos aeris, is often employed by the natives 
of the east, on account of the elegance of its 
leaves and flowers, and the exquisite odour which 
it diffuses, as an ornament, suspended by a silken 
cord from the ceilings of their rooms where, from 
year to year, it continues to vegetate, putting 
forth new leaves, new blossoms, a new fragrance, 
entirely supported by the moisture and gases of 
the surrounding atmosphere. Many of the na- 
tive plants of the east nearly support themselves 
in the same way; some of the mosses of this 
country almost do the same. The quantity of 
water consumed by plants when in a state of 
healthy vegetation, is in fact so great, that, if it 
was not for the gentle steady supply thus imper- 
ceptibly furnished to the soil by the atmosphere, 
vegetation would speedily cease, or only be sup- 
ported by incessant rains, Thus, Dr. Hales as- 
certained that a cabbage transmits into the 
atmosphere, by insensible vapour, about half its 
weight of water daily; and that a sunflower 
three feet in height transpired in the same period 
nearly two pounds weight. Dr. Woodward found 
that asprig of mint, weighing 27 grains, inseventy- 
seven days emitted 2,543 grains of water; a sprig 
of spearmint, weighing 27 grains, emitted in the 
same time 2,558 grains; a sprig of common 
nightshade, weighing 49 grains, evolved 3,708 
grains; and a lathyris of 98 grains emitted 2,501, 
It has been shown by the experiments of M. 
Saussure with some sprigs of peppermint, that, 
when supplied with pure water only, and allowed 
to vegetate for some time in the light, that they 
nearly doubled the portion of carbon they origin- 
ally contained. This they could have procured 
only from the atmosphere; and under these cir- 
only three parts.’ And this absorbent power of , cumstances, there is now little doubt of the cer- 
