or discs-the ploughing elements-encountered an obstacle, e.g., a stump, they would automatically rise over it, and having passed it would re-enter the ground automatically, or by means of apparatus, e.g., springs provided for that purpose. The stump-jump action in H. disc ploughs was obtained through an arm (on which the discs were mounted) pivoted on the axle or frame of the plough. The discs, by this means, could lift vertically up or down as the obstacle was encountered or passed. A reversible disc plough was one which provided for reversing the position of the discs from one side to the other. In a non-reversible plough, the earth is thrown in two directions, whereas in the reversible plough that is not SO.
The appellant's invention was, as already stated, for " an improved reversible stump-jump disc plough." It was described in the specification as plough to do the same work as those at present in use but of much simpler construction and easier to control." The specification then describes the plough specifically, and in detail, by reference to drawings incorporated in it. The first claim, which follows the description, is ' A stump-jump disc plough comprising, a frame, land wheels supporting said frame, a horizontal spindle carried by said frame, a stump-jump arm pivotally mounted on said spindle, a stem rotatably supported by said stump-jump arm, an axle member on said stem, a cutting disc on said axle member and means for rotating said stem to reverse said disc." Upon the true construction of this claim, there is no doubt, I think, that it is for a stump-jump disc plough limited to a special combination of parts. It is not for any system or principle of construction combining stump-jump action and reversibility. The question is whether the respondent has infringed this claim.
The respondent has made a stump-jump and reversible disc plough. The plough has an arm by means of which the stump-jump and reversible elements are connected to the frame of the plough by an ingenious ball joint connection, which permits pivotal movement for stump-jump action, and rotary movement for the reversal of the discs. In addition it has means for connecting the draught to the stump-jump, and reversing elements whereby the discs are main- tained at work in the ground by the pull of the horses, and rise against