Mr. Freeland taught me the secret of producing true cylindrical surfaces by grinding with a wheel. It was to let the swiftly revolving wheel traverse the surface as it rotated, touching only the highest points, and these very lightly. This avoided the danger of errors from the springing of either the piece or the wheel, which under strong pressure is sure to take place to some extent, even in the best grinding-machines. I have found this delicacy of touch to be a most difficult thing to teach the ordinary workmen. They often manage to produce by grinding a surface more imperfect than it was before. I took extreme pains to insure that the axes of the joint pins should intersect the axis of the governor spindle and those of the governor balls, and should be equidistant from the center of the counterpoise, these parts of the joints having been turned to true spherical forms by means of a circular tool-rest. For this purpose I employed a feeling-gauge, consisting of a cylindrical stem fitting the hole as drilled, with a curved arm projecting from this stem and terminating in a point that would rub on the external surface of the balls. By this means we almost always detected some slight inaccuracy, which was remedied by the use of a round file. The joint holes were afterwards finished with long reamers, the cutting portion of which was in the middle of their length. The front end of the reamer fitted the drilled hole and extended quite through the joint, so guiding the cutting edges as they entered, and the back end of the reamer filled the hole that had been reamed. I finally tested their alignment by bringing the last of the five joints together after the others had been united, when the forked link should swing freely to the ball without the least tendency in either direction from its exact place. This it always did. Some time afterwards I adopted the plan of dispensing with heads and washers on the joint pins, reaming the holes in the central portions of the joint slightly smaller than those in the arms and making the pin a hard fit in the former. There was never any tendency for a pin to get loose in the running of the governor. I also at a later date cut the counterpoise in two a short distance above the joints, so that the mass of its weight did not need to be started and stopped when the speed of the governor changed. I could not see, however, that this was of any advantage, although when the governor balls were pulled around by hand no motion was imparted to the mass of the counterpoise. The action was apparently quite perfect before. CHAPTER III Invention and Application of my Marine Governor.