quire. The one set of ridges terminate at this part, and the other are laid off from it in the new direction to be given. The ploughman, by means of his poles, as before, strikes his first set of furrows, terminating them at the furrow where the change of direction is to take place. From this furrow he strikes his second set of furrows, in the direction in which they are to run. The part where the opposite sets of furrows meet may be made an open furrow, or a raised-up ridge or headland, as circumstances may require.

The direction of ridges must generally be regulated by the sloping of the fields, and the lying of ditches or fences, so that they may promote the main purpose for which they are formed, the carrying off of surface water. But, other circumstances being alike, they should be made to lie as much as possible north and south, and as rarely as possible east and west; for, in the latter case, when the ridges are much elevated, the north side has a somewhat less favourable exposure than the south side.

Sometimes ridges are altogether dispensed with, either when the land is very dry, or when it is wished to keep it in grass, and give it the aspect of a park or lawn. In this case, the ploughs may either follow each other round the entire field, and terminate at the centre, or they may plough in large divisions, as in the case of cross-ploughing.

In ploughing very steep land, it is frequently laid in ridges diagonally across the slope, for the purpose of rendering the labour more easy, and of lessening the danger of torrents carrying away the

surface.

The precaution to be observed in this case is to make the ridges slope upward from the right hand, as from A to B, in the following figure, and not to the left hand, as from C to D. For, in the first case, when the labouring cattle are ascending the

steep, the plough is throwing the furrow-slice down hill; whereas, in the other case, when the cattle are ascending, they are raising the furrow-slice up hill, by which their labour is greatly increased.

Fig. 10.
B D

Besides the open furrows of the ridges, which act as channels for carrying off the water, it is necessary, where there are hollow places where water may stagnate, to form open furrows or channels. This is done by drawing a furrow with the plough in the direction most convenient for the purpose. A workman then follows with the spade or shovel, and carefully opens all intersections with other furrows, so that there may be a free communication between them.

Sometimes it is necessary that the furrow made by the plough be further deepened by the spade, so as to form a channel sufficiently large; and wherever headlands intercept the run of water, channels must be cut through them to the ditch or outlet, so that none may stagnate upon the ground. Attention to these details, in practice, is essential in all cases of tillage; and it manifests a want of skill and industrious habits in a farmer to suffer his lands to be injured by the stagnating upon it of surface water.-Low's Elements of Practical Agriculture.

CHAPTER XXI.

Harrow-Oultivator-Roller.

The Harrow.-This instrument succeeds to the plough in the order of description and the uses to which it is applicable. It consists of a frame of wood or iron, in which a certain number of teeth are fixed, which are pressed into the ground by their own weight and that of the frame. The instrument is intended to pulverize the ground which has been acted upon by the plough, to disengage from it the roots and other substances which it may contain, and to cover the seeds of corn and other cultivated plants.

The harrow is greatly more simple in its form than the plough. It is even an imperfect machine in any form of which we can construct it; yet it is of great utility in tillage, and should receive all those mechanical improvements of which its nature will admit.

The harrow performing its operation by means of a certain number of teeth moved forward in the ground, and pressed downward by their own weight and that of the frame in which they are fixed, the first questions that occur, in investigating the principles of its construction, are the form that should be disposed in the surmounting frame. Were it the purpose, in harrowing, solely to drag up the roots of plants and other substances from the ground, the best form, perhaps, that could be given to the teeth would be that of a thin wedge, tapering to the point like the coulter of a plough, and, like it, inclining forward. But although this construction might be the best calculated for tearing up roots

and other substances beneath the surface, it would not be so well fitted for covering the seeds and for breaking and pulverizing the ground, as when a broader surface was presented to the earth, and a greater movement given to its particles. The wedge for this purpose should be broad rather than thin. In order, therefore, to adapt the form of the teeth to this purpose-to the strength necessary to be given to them, and to the lateral or shaking motion to which they are subjected in passing over rough ground, as well as to their forward motion-it is conceived that the best form of them will be when their horizontal section is a square, whose diagonal is moved forward in the line of the harrow's motion; while they should gradually taper to a point, the forepart being kept straight, as in T, fig. 1.

With regard to the distribution of the teeth in the frame of the harrow, they should not be placed too closely together, for then they would be too much impeded by the obstacles opposed to them. Farther, they should be so disposed with relation to each other, as that one part of the instrument shall not be more interrupted than another. Again, their number should not be too great, because then their power to penetrate into the ground will be diminished, unless the weight of the whole instrument shall be increased in a corresponding degree. And, lastly, their length should not be greater than is necessary, because they will not on that account penetrate more deeply into the ground, unless the whole weight is also increased, and because this increase of length will give a greater power to the teeth, when encountered by obstacles, to split the frame in which they are fixed.

The harrows represented in Fig. 1, of which the frame is of wood and the teeth of iron, are formed

These harrows are constructed by Mr. Craig, of Galway, and sold at $15 the pair.