“it is not unusual to tread fields of a moderate 
size by the human feet; but this plan cannot be 
carried to any great extent. The superior sam- 
ple obtained from the dibble, compared to the 
drill, is by some attributed to the additional 
solidity the land receives from the treading of 
the children employed in the operation. In 
some districts of England, it is usual either to 
fold the sheep on the ground sown with wheat, 
between the sowing and the coming up of the 
crop, or to drive the flock repeatedly over it at 
that juncture, in order to give firmness to the 
soil and greater stability to the crop. By this 
means, wheat may be raised on land which is 
naturally too loose in its texture for the profit- 
able production of wheat. Some farmers, on 
_ light soils, prefer pigs for that purpose, as better 
calculated for the process than any other ani- 
mal, from their great weight, compared to the 
size of their feet. But in West Sussex, the 
lighter soils, in dry seasons, are trod by the 
plough-horses, when turning the seed-furrow. 
Three plough-horses, instead of going at length, 
draw the last-made plough-furrow abreast, and 
thereby tread or compress the line of soil they 
are turning. The advantages of treading, as 
more effectual than even rolling, in destroying 
the larve of insects, and preventing the har- 
bouring of vermin in the soil, cannot be ques- 
tioned. It may likewise contribute to check the 
vegetation of weeds: it prevents evaporation ;— 
and it is found, that the crops on land thus 
trod, are not liable to be rusted. It is certainly 
more applicable to dry light soils; but even in 
wet ones, when it is impossible to roll the land 
after it is sown, owing to the wetness of the sea- 
son, it may be trod afterwards by sheep.” 
TREE. Almost all subjects of any value or 
interest respecting trees are discussed in our 
articles Timpsr, ALBURNUM, DuURAMEN, Bank, 
Ascent or Sap, Lienin, Coppice, PLanrarron, 
Forest, Prantine, Germination, GrowrH, Dn- 
cay, AGE oF Purants, Woop, TRANSPLANTING, 
Pronine, Barxine, Frnume, and LanpscaPr- 
GARDENING, and in the articles on the several 
kinds of trees, both indigenous and exotic; and 
nothing is left to be done in this place except to 
note a few general facts respecting the size, 
growth, maturity, and indigenousness of trees. 
On ordinary soil and in ordinary circum- 
stances, the average height and diameter of the 
spruce fir, at the period of full growth or of full 
fitness for felling, is from 26 to 100 feet and 
471 inches; of the larch, from 26 to 100 feet 
and 30°3 inches; of the pine, from 16 to 65 feet 
and 34:1 inches; of the poplar, from 19 to 65 
feet and 31°8 inches; of the plane, from 16 to 48 
feet and 36:1 inches; of the oak and the elm, 
from 16 to 48 feet and 31°4 inches; of the birch, 
from 16 to 48 feet and 29:4 inches; of the beech, 
from 16 to 48 feet and 28'2 inches; of the lime, 
from 16 to 48 feet and 25:9 inches; of the ash, 
from 16 to 48 feet and 23°5 inches; of the wil- 
low, from 16 to 48 feet and 11:7 inches; of the 
chestnut, from 13 to 48 feet and 36:1 inches; of 
the maple, from 10 to 48 feet and 28'2 inches; of 
the service, from 13 to 39 feet and 17°6 inches; 
of the acacia-tree, from 13 to 26 feet and 19:2 
inches; of the hornbeam, from 10 to 23 feet and 
| 21°2 inches; of the mulberry, from 10 to 23 feet 
and 16:5 inches; of the wild pear, from 10 to 23 
feet and 14'1 inches; of the crab, from 6 to 20 
feet and 12'9 inches; and of the walnut, from 6 
to 16 feet and 36:1 inches. All trees, however, 
are greatly controlled in their size by soil, posi- 
tion, exposure, elevation, and climate; and some 
individuals of almost every species, as compared 
with all ordinary individuals of the same species, 
acquire very large dimensions. 
Young trees, in all favourable circumstances, 
manifestly grow with great rapidity; while 
all old ones appear to common observers to be 
quite stationary, or, like adult animals, to have 
entirely ceased to grow; and yet trees of every 
age, on till the actual commencement of decay, 
maintain a comparatively steady progress of 
growth, and acquire seasonal or yearly incre- 
ments to their bulk. Dicotyledonous trees, in 
particular, comprising all the kinds which thrive 
in the open air in Great Britain, make, all their 
life long, periodical additions to their substance 
in the form of concentric or superimposed layers 
of woody tissue; and not a few of them, va- 
riously influenced by the intrinsic powers of their 
constitution and by the extrinsic ones of their 
situation, make these additions much more 
bulkily when they are at a somewhat advanced 
age than when they are young. “ With a view 
to ascertain the amount of increase in the woody 
layers at different periods, De Candolle measured 
their thickness, and found that if the annual 
increase presented a certain regularity, it was 
still very far from being absolute even in the 
case of a single species. The oak especially 
offered striking anomalies; thus a trunk which 
had grown slowly in diameter was found to have 
increased more rapidly as it got older. He 
found young trees of the same species, the 
growth of which, very slow at first, by and bye 
became accelerated, and then fell off in a third 
period of their existence. From the whole of 
his observations, De Candolle concludes that the 
growth of our common European trees, having 
gone on with a certain rapidity to the age of 
from about 50 to 70 years, then became slower, 
but continued regular to extreme age. The in- 
equalities of growth, conspicuous in the different 
thickness of different rings, he thinks are mainly 
due to the kind of soil which the mass of the 
roots encountered in their progress, or the re- 
moval of other trees which grew in the vici- 
nity. The diminished thickness of the rings 
after trees have passed a certain age, he ascribes 
to the depth to which the roots have now pene- 
trated, and their consequent remoteness from 
the air; and farther, to the resistance opposed 
4 
