The apparatus was now ready for use, the corresponding points on the circle and the arc being numbered alike. By setting the first two points in any corresponding holes, the third point would show the corresponding position of that point of the link at which it was set. I thus set out the movements of six different points of the link, the highest being 12 inches above the trunnions. These represented the movements of the valves of the engine when the block was at these points in the link. The apparatus being firm, it worked with entire precision. To my surprise, it showed much the larger valve opening at the crank end of the cylinder, where the movement of the piston was slowest. That would not do; we wanted just the reverse. I called Mr. Allen in and showed him the defect. After considering it a few minutes, he said he thought it would be corrected by lowering the trunnions, so that their arc of vibration would coincide with the line of centers at its middle point, instead of terminating on it. This was done, and the result was most successful. The lead was now earlier and the opening wider at the back end of the cylinder, as the greater velocity of the piston at that point required, and the cut-offs on the opposite strokes more equal. The link has always been set in this way, as shown in the diagram. From this description of the link motion, it will be seen that the correct vertical adjustment of the trunnions of the link was an important matter. To enable this adjustment to be made with precision, and to be corrected, if from wear of the shaft-bearings or other cause this became necessary, I secured the pin on which these trunnions were pivoted to the side of the engine bed in the manner shown in the following figure. To hold the wedge securely, the surface of the bed below was reduced, so that the wedge was seized by the flange. The correct position of this pin was determined by the motions given to the valves. [Illustration: VERTICAL ADJUSTMENT OF SUSTAINING PIN FOR TRUNNIONS OF THE ALLEN LINK]