SUBSOIL-PLOUGHING. 
rectness of the conclusion of M. Berthollet, that 
plants, by means of their leaves, have the power 
of decomposing the water as well as the carbonic 
acid of the atmosphere, and furnishing with these 
elements new combinations. How essential a 
free access of the atmosphere is to the roots of 
plants, was long since shown by M. Saussure, 
who found that oxygen gas is absorbed by the 
roots of plants, as well as by their leaves, and 
that it is at the roots united with carbon, and 
transmitted to the leaves to be decomposed. 
Even the branches absorb oxygen: in its absence 
flowers will not even expand. The advantages 
of a free access of oxygen to the roots of plants, 
. has been still further shown experimentally : it 
has been proved that their vegetation is greatly 
increased by nourishing them with water im- 
pregnated with oxygen gas; hence, too, the 
superiority of rain-water. Some remarkable ex- 
periments were made by Mr. Hill, demonstrative 
of the great benefit plants derive from oxygen 
gas being applied to their roots. Hyacinths, 
melons, Indian corn, &c., were the subject of the 
experiments, The first was greatly improved in 
beauty, the second in flavour, the last in size, 
and all in vigour. This is another use of a free 
access of atmospheric moisture; for M. Hum- 
boldt has clearly shown that a dry soil is quite 
incapable of absorbing oxygen gas. Now, it 
must be evident, even to the most listless ob- 
server, that the more deeply and finely a soil is 
pulverized, and rendered permeable, the greater 
will be the absorption of both oxygen and watery 
vapour from the surrounding atmosphere. 
“And by facilitating the admission of air to 
the soil, another advantage is obtained, that of 
increasing its temperature. The earths are na- 
turally bad conductors of heat, especially down- 
wards. Thus it is well known, that, at the siege 
of Gibraltar, the red-hot balls employed by the 
garrison were readily carried from the furnaces 
to the batteries in wooden barrows, whose bot- 
toms were merely covered with earth. Davy 
proved the superior rapidity with which a loose 
black soil was heated compared with a chalky 
soil, by placing equal portions of each in the 
sunshine ;—the first was heated in an hour from 
65° to 88°, while the chalk was only heated to 
69°. This trial, however, must not be regarded 
as absolutely conclusive, since the surfaces of 
the black soils naturally increase more rapidly 
in temperature when exposed to the direct rays 
of the sun, than those of a lighter colour. A 
free access of air to all soils also adds to their 
fertility, by promoting the decomposition of the 
excretory matters of plants, which otherwise 
would remain for a longer period, to the annoy- 
ance of plants of the same species. 
“To the truth of these conclusions and labori- 
ous experimental researches of the chemist, does 
not the practical testimony of the ablest cultiva- 
tors of all countries and in all ages concur? 
Thus, in enforcing the advantages of rendering 
the soil more completely permeable by the at- 
mosphere, nearly two thousand years since M. 
P. Cato asked the Italian farmers, ‘ What is good 
tillage? To plough. What isthe second? To 
plough. The third is to manure.’ Cato, how- 
ever, mistook the cause of the benefit, for he 
says, ‘ He who stirs his olive-ground oftenest and 
deepest, will plough up the very slender roots; 
if he ploughs ill, the roots will become thicker, 
and the strength of the olive will go to the root.’ 
Virgil, where giving an erroneous explanation of 
the advantages of paring and burning, says, 
‘The heat opens more ways and hidden vents for 
the air, through which the dews penetrate to 
the embryo plants.’ Do not, at this very period, 
Lord Leicester and all the best of England’s agri- 
culturists, find the greatest advantage from stir- 
ring the ground between their rows of drilled 
turnips, for the sole purpose of promoting the 
access of the air to their roots; and that, too, on | 
soils where a weed is hardly to be seen? Is not 
one great object of fallowing to produce, by pul- 
verizing and deepening the soil, the same result ? 
Did not Jethro Tull labour long, and sometimes 
too sanguinely, in illustrating the same position ? 
And does he not support the subsoilers’ conclu- 
sions when he says,—‘ I have had the experience 
of a multitude of instances, which confirms it so 
far, that Iam in no doubt that any soil (be it 
rich or poor) can ever be made too fine by tillage. 
For it is without dispute, that one cubical foot 
of this minute powder may have more internal 
superficies than a thousand cubical feet of the 
same or any other earth tilled in the common 
manner; and I believe no two arable earths in 
the world do exceed one another in their natural 
richness twenty times; that is, one cubical foot 
of the richest is not able to produce an equal 
quantity of vegetables, ceteris paribus, to twenty 
cubical feet of the poorest; therefore it is not 
strange that the poorest, when, by pulverizing, 
it has obtained one hundred times the internal 
superficies of the rich untilled land, should ex- 
ceed it in fertility; or, if a foot of the poorest 
was made to have twenty times the superficies 
of a foot of such rich land, the poorest might 
produce an equal quantity of vegetables with the 
rich. Besides, there is another extraordinary 
advantage when a soil has a larger internal 
superficies in a very little compass; for then the 
roots of plants in it are better supplied with 
nourishment, being nearer to them on all sides 
within reach, than it can be when the soil is 
less fine, as in common tillage; and the roots in 
the one must extend much farther than in the 
other; to reach an equal quantity of nourish- 
ment, they must range, and fill, perhaps, above 
twenty times more space, to collect the same 
quantity of food. But in this fine soil, the most 
weak and tender roots have free passage to the 
utmost of their extent, and have also an easy, 
due, and equal pressure everywhere, as in water.’ 
“And it is fortunately in our power to prove 
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