The chief of these rules are given below,[149] from [p121] which it will be seen that in the co-tillage the team, as in England and Scotland, was assumed to be of eight oxen. And those who join in co-ploughing must bring a proper contribution, whether oxen or plough irons, handing them over during the common ploughing to the charge of the common ploughman and the driver, who together are bound to keep and use everything as well as they would do their own, till, the co-ploughing being done, the owners take their own property away. «Rotation in 'erws' according to the oxen.» So the common ploughing was arranged. But how was the produce of the partnership to be divided? This, too, is settled by the law, representing no doubt immemorial custom. The first erw ploughed was to go to the ploughman, the second to the irons, the third to the outside sod ox, the fourth to the outside sward ox, the fifth to the driver, the sixth, seventh, eighth, ninth, tenth, and eleventh to the other six oxen in order of worth; and lastly, the twelfth was the plough erw, for ploughbote, _i.e._ for the maintenance of the woodwork of the plough; and so, it is stated, 'the tie of 12 erws was completed.' Further, [p122] if any dispute should arise between the co-tillers as to the fairness of the ploughing, the common-sense rule was to be followed that the erw which fell to the ploughman should be examined as to the depth, length, and breadth of the furrows and every one's erw must be ploughed equally well. Here, then, in the Welsh laws is the clearest evidence not only of the division of the common fields by turf balks two furrows wide into the long narrow strips called _erws_, or acres, and roughly corresponding in shape, though not in area, with those on English fields, but also of the very rules and methods by which their size and shape, as well as the order of their ownership, were fixed in Wales. «It is the method of division of the results of co-tillage.» And this order in the allotment of the erws turns out to be an ingenious system for equitably dividing year by year the produce of the co-operative ploughing between the contributors to it. Now, without entering at present into the question of its connexion with the tribal system in Wales, which will require careful consideration hereafter, several interesting and useful flashes of light may be drawn from this glimpse into the methods and rules of the ancient Welsh system of co-operative ploughing. «The size of the team necessitates co-operation,»