seldom employed, but an improved method of applying the soam has been adopted in its place, which is represented by fig. 202, where a is the bridle of the plough, with its swivel hook. A pulley b of cast iron, 6 inches diameter

mounted in an iron frame, of which an edge-view is given at m, is attached to the hook of the bridle. A link chain c is rove through the frame of the pulley; and to one end of it, the short end, is hooked the main swing-tree d of a set of common trees for the plough horses. The other end of the chain passes forward to a sufficient distance to allow the leading horses room to work; and to it is hooked the second set of common swing-trees at e for the leaders. In the figure, a part of the chain, from f to g, is broken off; but the full length is about 11 feet. In this yoke, the trace-chains of the nigh-side hind horse are hooked to the swing-trees at h h, and those of the off-side horse at ii, the leaders being yoked at k k and ll respectively. In this arrangement, the balance of forces is perfectly preserved; for the hind horses and the leaders, as they pull

at opposing ends of the chain passing round a pulley, which must inevitably be always in equilibrium, each pair of horses has an equal share of the draught; and from the principles of the common swing-trees through which each pair acts, the individual horses must have an equally perfect division of the labour, unless this equilibrium has been removed for the purpose of easing a weaker horse. In order to prevent either the hind horses or the leaders from slipping too much a-head, it is common to apply a light check-chain o, of about 15 inches long, connecting the two parts of the main-chain, so as to allow only a short oscillation round the pulley, which is limited by the check-chain. When this is adopted, care should be taken never to allow the check-chain to remain upon the stretch; for if it do so, the advantage of equalization in the yoke is lost, and it becomes no better than the simple soam. In all cases of using a chain, that part of it which passes forward between the hind horses must be borne up by means of attachment to their back bands, or suspended from their collars. (1133.) Mr Stirling of Glenbervie, Stirlingshire, recommends a method of yoking a team of four horses in pairs, the arrangements of which are represented in fig. 203; a is part of a main swing-tree of the common length, ba small swing-tree about 4 inches longer than the usual length, but both mounted

Fig. 203.

d

b

a

THE SWING-TREES ALSO FOR FOUR HORSES.

in the usual form, except that, at each end of the small swing-trees, cast-iron pulleys c c, of 3 or 4 inches diameter, and set in an iron frame, are hooked on to the eyes of the swing-tree. The common trace-chains are rove through the frames of these pulleys, as in the figure, the ends d d of the chains are prolonged forward to the proper length for the nigh hind horse, and the ends e e are extended to the nigh leader. At the opposite end of the main swing-tree, which, in this figure, is cut off, the same arrangement is repeated for the off-side horses. The principle of action in this yoke is simple and effective, though different in effect

from the former. There the two hind horses are equalized through the medium of their set of common swing-trees. The leading horses are alike equalized by their set, and thus the two pairs balance each other through the medium of the soam. Here, on the other hand, the two nigh-side horses have their forces equalized through the trace-chains which are common to both by passing over the pulleys c c, and the same holds in respect to the two off-sides. The couple of nighside and of off-side horses, again, are equalized through the medium of the one set of swing-trees. In both, therefore, the principle of equalization is complete, but there is a trifling difference in their economy. In the yoke, fig. 202, which I call the cross balance yoke, the soam-chain and pulley are the only articles required in addition to the every-day geer. In that of fig. 203, which I call the running balance yoke, there is first the set of swing-trees, which, as they have to resist the force of 4 horses, must in all their parts be made stronger than the common set, agreeably to the rules before laid down; and to which is added the 4 pulleys, all of which are applicable only to this yoke. The trace-chain, though not necessarily stronger than those for common use, is required about three times longer than single horse-chains, that is to say, four horses will require the chains of six; but the chains of the leaders are more conveniently supported when they pass along the sides of the hind horses, and it is free of the set of swing-trees which dangle behind the leaders, of the method fig. 202.

(1134.) In cases where 6, 8, and even 12 horses are required, such as for trenching, subsoil-ploughing, and especially draining with the plough, the yoking is accomplished by modifications and extension of the principles here laid down; for example, a team of 6 can be very conveniently applied with equalized effect by employing the compensation levers of fig. 202, along with 3 single swing-trees with pulleys at each end and running trace-chains, as in fig. 203.-J. S.]

29. OF PLOUGHING STUBBLE AND LEA GROUND.

"'Tis time to clear your ploughshare in the glebe."

GRAHAM.

(1135.) When you take an extensive glance over the fields immediately after harvest, when the crop has been gathered into the stackyard, you perceive that a large proportion of them are in stubble, whilst others are occupied by grass, turnips, and young wheat. On examining the stubbled fields particularly, you will observe young grass amongst the stubble in some fields, and nothing but stubble in others. You could not, of yourself, discover at once, that these various states of the fields bear a certain proportion to one another, though they really do; and the cause of their being in those proportions, is, that they are cultivated under what is termed a "regular rotation of crops," which, when followed

out, necessarily causes every field, in its turn, to carry the same series of crops. The numbers composing the series depend on the nature of the soil, and it shall be my duty to make you acquainted with them in due time. Meantime, suffice it to intimate, that when the stubble is in that state, the beginning of the agricultural year is arrived, when certain parts of it must undergo a change, and be transformed into those which follow the ones you find them in. Now, that part of the stubble-land which is devoid of any crop is the first to undergo a change, and it is effected by the plough, not at random, but by the application of those principles which have already been explained to you when we considered the "various modes of ploughing land into ridges," from pages 464 to 481, where, as you may remember, the mode of ploughing was said to be determined by the nature of the soil and subsoil. The stubble-land is generally all ploughed before the lea is commenced with, and that part which is to bear the potato-crop next spring is first ploughed, then that for the turnip-crop, and last of all for the bare fallow, when there is any.

(1136.) On clay soil you will find the stubbled ridges of a rounded form, having been at least twice gathered up, fig. 139; and the way to keep them in a dry state during winter, on a considerable declivity, is to cleave them down without a gore-furrow, fig. 140, and without a mould-furrow, fig. 134, or to cleave them down with gore-furrows, fig. 141, and mouldfurrows, when clay-land is flat. On less strong soil, casting with a gore-furrow (831.) will preserve land dry whether it be flat or on a declivity. On light loams, casting without gore-furrows, fig. 135, will serve the purpose. And on sandy and gravelly soils, crown and furrow (827) is the most appropriate mode of ploughing stubble. It is rare that stubble-land is subjected to any other mode of ploughing in winter. Snow should never be ploughed in, nor the ground turned over when affected by frost, nor should strong clay soil be stirred when very wet, as it is apt to become very hard in spring, and of course more difficult to work.

(1137.) In every variety of soil, ploughed in the forms just described for winter care should be taken to have plenty of channels, or gans or grips, as they are usually termed in Scotland, cut in the hollowest places, so as surface-water may have them at every point by which to escape into the nearest open ditch. The gaws are first drawn by the plough laying them open like a feering, taking, in all cases, the hollowest parts of the ground, whether these may happen to cross the ridges or go along the open furrows; and they are immediately afterwards cleared

out with the spade of the loose earth left by the plough, and cast abroad over the surface. The fall in the gaws is made to tend towards a point or points best adapted to carry off surface-water by the shortest route, and do the least injury to the soil. The ends of the open furrows which terminate at the furrow along the side of the lowest head-ridge, as well as this furrow itself, should be cleared out with the spade, and cuts made at the hollowest places across the head-ridge into the ditch. This precaution of gaw-cutting should never be neglected in winter in any kind of soil, the stronger soils requiring more gaws than the lighter ; for as there is no foreseeing the injuries which a single deluge of rain may commit, it is never neglected by the provident farmer, though many small farmers, to their own loss, pay little heed to the necessity of its observance.

(1138.) With regard to the ploughing of lea ground, the most usual form in strong soil is to cast with a gore-furrow, fig. 136, and on less strong soil the same form of ploughing without a gore-furrow, whilst on the lightest soils of all, the crown and furrow is in most common use (827.). Gathering up is a rare form of furrow for lea, though it is occasionally practised on strong soil after gathered up or cast ridges, when it is a rather difficult operation to plough the furrow-brows and open furrows as they should be. The oldest lea is first ploughed, that the slices may have time to mellow by exposure to the winter air, and that which is on the strongest land is for the same reason ploughed before that on light. Lea should never be ploughed in frosty weather,. that is, as long as the ground is at all affected by frost, nor when there is rime on the grass, nor when the ground is very soft with rain; because when ice or rime is ploughed down, the non-conducting property of grass and earth, in regard to heat and cold, preserves the ice in an unaltered state so long as to chill the ground to a late period of the season, and when the ground is too soft, the horses not only cut it into pieces with their feet, but the furrow-slice is apt to be squeezed out of its proper shape by the mouldboard. Nor should lea be ploughed when hard with drought, as the plough in that case will take too shallow a furrow-slice, and raise the ground in broad thin slabs instead of proper furrow-slices. A semi-moist state of the ground in fresh weather is that which should be chosen for ploughing lea. Gaws should not be neglected to be cut after lea-ploughing, especially in the fields first ploughed, and in strong land, always whether early or late ploughed.

(1139.) It is a slovenly though too common a practice to allow the headridges to remain unploughed for a considerable time after the rest of the field has been finished ploughing, and the neglect is most fre