370 
produced by natural causes, what is to prevent 
the consolidation of subsoil by the percolation of 
water, although it had been loosened by the sub- 
soil plough, especially when placed under a su- 
perincumbent weight of earth? Clay soil having 
a natural affinity for water, its texture does not 
‘clap’ or consolidate so obviously by the action 
of water as friable soil, though it poaches on the 
surface much more readily. Air is found in the 
earth at the lowest depths; but that its action 
can be so sensible on loosened subsoil, placed 
under a thick stratum of earth, as to admit ofa 
comparison with those chemical changes which 
it effects on the surface of the soil in fallow, 
‘owing to its exposure to the action of the wind 
and rain,’ especially when the essential amelior- 
ating element of light is necessarily excluded 
from the subsoil, is a proposition to which few 
scientific minds would give assent. 
“ Subsoil-ploughing is surely not ‘applicable to 
ail qualities of subsoil.’ What could it effect on 
a subsoil of trap, of which there are numerous 
instances in this country and Ireland? There 
are subsoils, both alluvial and diluvial, so occu- 
pied with erratic blocks, as to render the admis- 
sion of any kind of plough impracticable. Those 
in some parts of Kincardine and Aberdeenshires, 
and the county of Antrim in Ireland, are so full 
of primitive and trap blocks as to form a sort of 
causeway under the arable soil. The subsoil of 
gravelly deposits is frequently full of large and 
land-fast blocks of stratified rock. From 14 to 
16 inches under the surface is the depth recom- 
mended by Mr. Smith for subsoil-ploughing, and 
6 inches of earth is thought desirable to be be- 
tween the sole of the plough and the tiles, the 
depth to the tiles thus being 22 inches; but 
there are many persons who make their tile 
drains only 24 inches in depth, in which cases, 
were they to practise subsoil-ploughing as here 
recommended, they would inevitably destroy 
their drains. It would, of course, be foolish to 
make the attempt; and yet the probability of 
such attempts being made by inconsiderate per- 
sons, shows the imminent danger of recommend- 
ing the indiscriminate use of the subsoil-plough. 
Subsoil-ploughing is like an edged tool, which is 
only safe in the hands of an experienced operator. 
“Tf depth of soil is all that is desired to be ob- 
tained by subsoil-ploughing, that object may be 
more easily and effectively obtained by plough- 
ing a little deeper than usual with the common 
or with a four-horse plough. This implement is 
more easily drawn than a subsoil-plough, inas- 
much as it chiefly works in the surface soil; and 
a deep arable soil is more effectually procured 
by it, in a shorter period of time, inasmuch as it 
brings some of the subsoil, of whatever quality it 
may be, ‘as in fallow,’ to more thorough ‘ expo- 
sure to the action of the wind and rain’ and 
light, than can be done by the subsoil-plough 
with its once repeated subterranean operation. 
Some farmers, it is true, object to bringing to 
SUBSOIL-PLOUGHING. 
the surface any species of subsoil, as being de- 
leterious to vegetation. This objection has no 
validity in any case where the soil and subsoil 
have been thorough drained; and it is less valid 
in cases where the subsoil is nearly similar to 
the surface soil, as carse clays, black mould, loams. 
and such like. But however ‘tilly’ the subsoil 
is, when mixed in a small proportion at a time, 
in comparison with the arable soil, after being 
exposed to the meliorating influence of the light 
and air, it can never materially injure vegetation. 
But for our part, we see no necessity for wishing 
an inordinate depth of workable soil. Six inches 
form a fair average furrow depth; and if there 
is as much below it of well dressed soil, plenty of 
scope will be afforded for the rumination of the 
roots of the plants usually cultivated. We con- 
sider the quality or heart of the soil beyond the 
depth of the usual plough furrow, of much more 
importance than its quantity; and, of course, 
six inches of subsoil is much more easily put in 
heart than sixteen. We have ploughed deep 
black mould, resting upon retentive clay, sixteen 
and ten inches deep, at different parts of the 
same field, with a four-horse plough, after it had 
been drained, and we could perceive no advan- 
tage on the crops for years after, on the deeper 
portion. Most of the plants which are cultivated 
in the fields, being fibrous rooted, do not require 
great depth of soil to thrive in. We have, in- 
deed, traced the root of broad red clover, six 
feet in depth, through a fissure in a bank of clay 
loam, which had been carried away by the irrup- 
tion of a rapid stream in time of flood; but the 
plant which sent forth this long foraging root 
was no larger than its neighbours. We have 
followed the tap-root of a wheat plant for a foot 
through the soil, but its produce was not greater 
than that of others around it. These facts are 
not marvellous, because, had the energies of those 
plants which were exerted in the prolongation 
of root, been directed to the formation of leaves 
or seeds, their products would have been more 
valuable. It was the scantiness of food that im- 
pelled them to roam abroad in search of it; had 
they found abundance of food around their roots, 
like abundantly fed fowls, they would have had 
no temptation to wander so far from home. 
“Whilst expressing our convictions on the 
inutility of subsoil-ploughing, we have been fre- 
quently interrogated, would you not break the 
pan that is below? Break it up and bring it to 
the surface by all means, if it is within reach of 
common ploughing, whether the land has. been 
thorough-drained or not. But all this appre- 
hension of the moorband pan is founded on an 
erroneous conception of its origin. How does it 
originate? It is never found in subsoils of pure 
clay, of black mould, of hazel loams, of sand or 
gravel. It is quite impossible it should be found 
in such situations. The pan or crust is a de- 
position of iron, and can only be deposited on 
such subsoils as admit of a certain degree of per- 
