CHAPTER II

The Evolution and Manufacture of the Central Counterpoise Governor. Introduction of Mr. Richards.

When the stone-dressing machine was started a difficulty presented itself. The governor was in constant motion a short distance up and down, causing the engine to oscillate, running alternately too fast and too slow. There was nothing that should have caused this action, so far as I could observe. The load on the engine was constant. However the work done on the stone may have varied, the work of the engine was to lift the hammers, and these, being lifted successively, presented a uniform resistance. The oscillation was not very great, as nearly as I can remember about 12 per cent. of the speed; which would give to each hammer a variation of thirty-six blows per minute. This, however, produced a waving surface on the stone. The more rapid the blow, the stronger it was and the deeper the cut. These waves were slight, only about ¹⁄₅₀ of an inch variation in depth, but yet it was not possible for our rubbing-machine to grind them off without great loss of time. So we had to employ three or four stone-cutters to chisel off these ridges, which were about 4 inches apart.

It was evident that this oscillation must be stopped. I tried to remedy it by changing the pressure of the steam, and then by changing the pulleys so as to run the engine faster, the speed of the governor, however, necessarily remaining the same. But these had no effect. Having exhausted my own stock of ignorance on the subject, I applied to professional experts for more, and I got it. Three persons, who I supposed ought to know, and who probably did know, all that was then known on the subject, gave me the same advice. It was that I should get a larger engine and agreat deal larger fly-wheel. This advice did not seem to me reasonable. I knew that the engine was large enough, because while the governor was in the lowest position, in which it did not open the throttle entirely by any means, the machine ran too fast. They then told me I must have a heavier fly-wheel at any rate, and they explained to me that the fly-wheel performed two offices—one to carry the crank over its dead centers with an approximately uniform motion, and the other to give the governor time to act. I replied that the engine passed its dead centers with absolute uniformity then, as nearly as I could see, and as was shown by the surface of the stone, and consequently for that purpose the fly-wheel I had must be sufficient. The oscillations were regular, occupying about 30 revolutions of the machine, or 6 seconds of time, and had no connection with the dead centers, and I did not see why the governor should require any time to act. They told me that all governors required time to act, of course.

I then examined the governor more critically, and made up my mind that its action was hindered by friction in the driving-joints at the top of the spindle. These joints were about 4 inches apart, on opposite sides of the spindle, and were of a character in which the force transmitted through them to drive the balls produced a pinch between the broad faces of the joints. The governor could not act until by change of its speed it had accumulated force enough to overcome this pinch, and then it moved too far. Again I applied to my authorities for some way of getting rid of this friction. They told me that was easy enough. All I had to do was to put a yoke on the governor spindle, through which the governor arms were threaded and by which the driving pressure was applied close to the balls. So for the first time I took their advice and had a yoke put on the governor. I could not discover that this helped the matter at all. The improvement was too trifling to be noticed. I also saw clearly enough why this was so. The pressure applied was lighter than that applied through the joints, but it was also applied at a correspondingly increased distance from the axis, so that the effect in retarding the action of the governor was substantially the same.

I saw that if I got any relief I must find a way to it myself. So I began studying the subject of governors. My engineeringlibrary at that time consisted of Haswell’s Engineers’ Pocket Book. What little book-knowledge I had respecting mechanics I had learned from Haswell. I turned to Haswell and read what he had to say about governors. I learned that they were conical pendulums and made half as many revolutions in a minute as the vibrations of a pendulum whose length was equal to the height of the cone, the base of which was the plane in which the center of oscillation of the balls and arms revolved, and its apex the point of intersection of the axes of the arms, if produced upward, and that their revolutions varied inversely as the square root of the height of this cone. I did not see that this got me out of my difficulty at all. I then referred to the subject of centrifugal force, with which I had made some acquaintance before, and I read this champion mind-muddler: “All bodies moving around a center or fixed point have a tendency to fly off in a straight line. This is termed centrifugal force.” This did not help me any more, nor interest me much at that time.

But I read further that the centrifugal force of a body revolving in any given circle varies as the square of the speed. “Thus a body making 10 revolutions per minute will exert four times as much centrifugal force as will be exerted by the same body making 5 revolutions per minute.” The governor on my engine was making 50 revolutions per minute, and in thinking the matter over it occurred to me that if the governor could be run as fast as my machine, namely, at 300 revolutions per minute, the centrifugal force of one pound would be as great as that exerted by 36 pounds at 50 revolutions per minute. I cried, “Eureka! I have found it.” One-pound balls in place of 36-pound balls would be easily driven. I told my experts of the great find that I had made, and they laughed at me. They told me I ought to know that the momentum of the balls increased in the same ratio with their centrifugal force,MV²being the expression common to both, so, in the same circle, while the centrifugal force of the balls at 300 revolutions per minute would be 36 times greater than at 50 revolutions, it would require also 36 times the force to drive them, and that I would gain nothing by my proposed change, but instead I would have to rotate also the weight that I would need to use to hold the small balls down, and the last casewould be worse than the first. This staggered me, and I pondered awhile what I should do.

I had a friend living near by on Fourteenth Street, west of Seventh Avenue—a Mr. Thompson, a mathematician and the author of a series of mathematical books then largely used. So I called upon him and stated my trouble and asked his advice. He illuminated the subject to me as follows: “You seem to be a persevering young man; keep hard at it and you will solve the difficulty by and by.”

In my despair I just had before me this one thought: The friction must be cured at any rate. After a time I thought that if I made a long joint at the top embracing the center of gyration of the counterpoise, so that the pressure required to drive the balls and counterpoise would be applied at some distance from the axis of the spindle and for that reason would be much lighter, and also would be normal to the surface of the joint-pin instead of being a pinch between opposite faces, the difficulty would be cured, as the force to overcome the friction would be exerted at the ends of levers 50 or 100 times the radius of the pin. I felt so sure of this that I risked making a governor with a single joint at the apex of the cone, as originally employed by Watt, thus making the governor more sensitive, as the height of the cone would not be changed at both ends, still fortunately holding to my little balls and high speed, though I cannot tell why. The joint at the top I made 6 inches in length.

When this governor was started, the trouble absolutely vanished. The engine ran with perfect uniformity while the load was constant. I use the adjective “perfect” advisedly, for the governor slide was as motionless on the spindle as if it were screwed tight, and the governor proved to be the most sensitive possible index of the variations of speed. When the belt was thrown off to the loose pulley the engine ran idle. The counterpoise then rose promptly but gently to its fixed highest position, and stood there motionless until the belt was thrown on and the hammers were started, when it moved as gently but promptly down to its lower position and stood there again motionless so long as the hammers were running. We could not detect by the eye the variation in speed that caused this action of the governor. The heaviest loadon the engine, however, was dragging rapidly the two tables loaded with stone. This caused the governor to settle still further, but always the motion of the engine seemed to be the same so far as I could detect. The surface produced on the stone left nothing to be desired. The machine cut true planes, free from any windage, and the surfaces were left so smooth that the rubbing-machine had but little to do, and kept up with the cutting-machine very easily. The governor fascinated everybody who witnessed its operation.

The First Porter Governor.

I first made the drawing for the governor with the weight hanging to the slide. Mr. John McLaren, a machinist who had donegood work for me, when I showed it to him said, “Why don’t you turn your weight upside down and put it between the arms?” I was not long in acting upon this suggestion, and that made the Porter governor complete. I had it described and illustrated in theScientific American. They took a photograph of it as photographs were taken in those days—that is, they sent their artist up to make a sketch of it, and this sketch (shownhere) and description will be found in theScientific Americanof October 9, 1858. This governor has never been changed by me except in the shape of the counterpoise.

I believed the mathematics of my advisers to be sound, and that the perfect action of the governor was obtained entirely by the long driving-joint, which I supposed would have enabled the 36-lb. balls at 50 revolutions per minute to do just as well as 1-lb. balls at 300 revolutions, but I never tried the experiment.

In that belief I remained for 50 years. Now, at the age of over 80 years, after long rest from business activities, in revising these reminiscences for publication, the idea has first occurred to me, and has grown into a conviction, that my advisers were wrong here as they had been in every other respect. They overlooked the fact that the angular velocity of the driving-joint increased equally with that of the balls, so that the ratio between them would remain constant. The law that the driving force required increases as the square of the speed imparted applies only to the original source of power, as, to the force of the steam exerted in the cylinder of an engine, the motion of the piston remaining the same, and to the transmitting belts or gears whose speed also remains the same. At all these points the force exerted must increase as the square of the speed imparted; but this does not apply to the pressure exerted in the governor joint. Its speed does not remain the same, but increases with that of the balls. So, while the centrifugal force of the balls, changes in which produce the vertical movements of the counterpoise, varies as the square of the speed, the force required to be exerted in this joint to drive the balls, and which produces the friction to retard these movements, does not increase at all, whatever the speed of revolution may be. This fact, unobserved by me or any one else so far as I ever heard, has all the time been the secret, a pretty opensecret when once seen, of the surprising combination of sensitiveness and stability in the action of this governor which has led to its general use, and at which I myself have never ceased to wonder because I was ignorant of its cause. This, however, was not the only time that I builded better than I knew.

I can imagine some persons, after having read the above explanation, to say, some of them perhaps flippantly, and some possibly sneeringly, “To a properly educated engineer this is obvious at a glance.” I think it will be so hereafter, but has it been so hitherto? If any one will produce the record of its observation I will cheerfully yield to him the priority and will congratulate him upon it.

Some things, however, make me doubt if this observation has ever been made. At the London Exhibition of 1862 this governor attracted much attention from its novel appearance, rapid rotation and remarkable action. Many engineers spoke to me about it. In their conversation I observed two things: first, no one ever asked me a question, but every one explained its action to me; and second, while each had an explanation of his own to make, they all agreed in a fundamental respect. Their minds ran in the same groove. They considered the governor only in its theoretical action. No one ever took notice of the incident of friction, which was the controlling factor. An improved governor was in their view one contrived in some way to free the governor from the limitation to its action, which is imposed by the law of the conical pendulum, and every one explained to me how my governor was adapted to do this.

The following illustrates this universal view among English engineers:

In the Appendix to the 10th edition of Rankine’s “Manual of the Steam-engine and other Prime Movers,” published in 1882, one reads as follows: “Isochronous governors. The ordinary governor is not isochronous; for when, in order to adapt the opening of the regulating-valve to different loads, it rotates with its revolving pendulums at different angles to the vertical axis, thealtitudeof the cone assumes different values, corresponding to different speeds.The following are expedients for diminishing or removing this defect.

1.Loaded Governor(Porter’s).—From the balls of the common governor, whose collective weight is (say)A, let there be hung by a pair of links of lengths equal to the pendulum arms, a load,B, capable of sliding up and down the spindle, and having its center of gravity on the axis of rotation. Then the centrifugal force is that due toAalone, and the effect of gravity that due toA+ 2B; consequently the altitude for a given speed is increased in the ratioA+ 2B:A, as compared with that of a simple revolving pendulum; and a given absolute variation of altitude in moving the regulating-valve produces a smaller proportionate variation of speed than in the common governor.”

That is the whole of it. Respecting this I have to say:

1st. The vertical motion of the counterpoise (variation of altitude), if the links had also a single joint at the bottom, could not be either more or less than twice that of the balls, which equal lengths of the arms and links give also in the common governor, so in this respect the governor is no improvement.

2d. No notice is taken of the small size of the balls or of the speed of rotation.

3d. Professor Rankine is not responsible for this absurd piece of reasoning.

4th. It only shows how far the English engineering mind has been from considering the subject of hindrance to the governor action from friction.

My governor works within the law of the conical pendulum. I never dreamed of attempting in this form of governor to avoid it. In fact it is this law which gives to the governor its action. A change of speed is necessary to produce a motion of the counterpoise. But as the governor was designed by me, this change of speed is very small, probably no more than is required for stability, and is not sensible in any way except in the motion of the counterpoise itself, which is simultaneous with the most minute changes of speed.

Quite a variety of modifications of this governor are being made in this country, but I think not elsewhere. The makers have been kind enough to invent the name “the central counterpoise governor.” For this I feel greatly obliged, as I should be mortified to find my name attached to any of them. Their actionis always more or less unsatisfactory, sometimes very much so. But I do not think it likely that the secret of the remarkable action of the Porter governor has been detected by any of these people.

I am glad that this was not explained to me at first; if it had been I might not have thought of the single long driving-joint, which is a valuable feature.

When the stone-dressing machine proved to be valueless, as already described, I found myself out of business; but the governor had attracted so much attention and had been so favorably received that I thought I could establish a business of manufacturing these governors, and I am proud to say that the gentlemen already associated with me and who had lost their money in the abandonment of the stone-dressing machine were so decidedly of the same opinion, and I had won their confidence to such an extent, that they furnished the money to enable me to establish this manufacture.

I rented a shop on the second floor of a triangular building on Thirteenth Street, at the junction of Hudson Street and Ninth Avenue, owned by Mr. Herring, the safe-manufacturer, the lower part of which was occupied by him for his own business. This was a large room and had light on three sides.

I proceeded to equip this shop with the necessary tools, some of which I purchased of Mr. Freeland, then considered the best toolmaker in the United States, and who had gone to England and worked for some years as a journeyman in the celebrated Whitworth Works, in Manchester, for the purpose of learning everything that was known there. Those which Mr. Freeland could not supply I obtained from Geo. S. Lincoln & Co., of Hartford, Conn.

During the time these tools were building I was waited upon by Mr. Chas. B. Richards, who was then removing from Hartford to New York to establish himself as a designer of machinery, and who brought me a letter from Geo. S. Lincoln & Co. I was at that time engaged in scheming as well as I could a machine for drilling the arms and balls and counterweight and spindle of my governor, and immediately employed Mr. Richards to assist me in getting out the drawings for this machine. This he did quite to my satisfaction,and the machine was made by Geo. S. Lincoln & Co., Mr. Pratt, for so many years head of the firm of Pratt & Whitney, afterwards the Pratt & Whitney Company, being then their foreman; so that all my tools from that concern were made by Mr. Pratt. He also cut for me superb iron patterns for the governor gears.

This machine always interested me very much. It solved every problem which was involved in the perfect and rapid performance of these operations. It had two parallel spindles running horizontally in the same plane, one fixed and the other adjustable. Distance pieces laid between the spindle heads insured the equal length of the arms of all governors of the same size. The table was made with a back to it, so that, a parallel block being laid on the table behind the arms, these were always brought in position parallel with its back. The arms were supported on blocks of proper height. These provisions insured that the joint-holes, which were drilled simultaneously, should intersect the axes of the arms and of the balls and spindle at right angles. This machine fitted up all the governors that I ever made. I gradually built up an excellent business in their manufacture, on account of the extreme pains taken to produce perfect work, so that the governors always gave the highest satisfaction.

I think of only one instance to the contrary. I sold a governor to Mr. Winslow, of Troy, afterwards of the firm of Corning & Winslow, the first manufacturers of Bessemer steel rails in this country under the inspiration of Mr. Alexander L. Holley. Soon after this governor had been shipped I received a letter from Mr. Winslow telling me that the governor would not answer at all, and I should come and see about it. I found the governor had been placed on a second-hand Burden engine, which was a well-known type of horizontal engine at that time, made in Brooklyn. The engine had been built to make 50 revolutions per minute, but being a great deal too large for their use they had reduced the speed to 25 revolutions per minute, and the complaint was that every time the crank passed its centers the governor dropped to its seat. I told them what I thought the difficulty was; that any one could see that the engine very nearly stopped as the crank passed its centers, and the governorhadto drop. To show them this action, I disconnected the governor from the valve and throttled the engine by hand, and showed them that the governor, when not connected with the throttle-valve, rose and dropped on every stroke, in the same way as when connected. They asked me what I was going to do about it. I told them I should do nothing about it; that I presumed they might possibly get a governor somewhere that would stand that alternation of speed without winking, but they had better send mine back, because it was not made for any such service.

Charles B. RichardsA.D. 1858

The following is an amusing illustration, doubtless an extreme one, of the degree in which the lay mind may be incapable of mechanical perception. My governors were usually set on the engine bed of horizontal engines near the shaft, and were connected with the throttle-valve over the cylinder by means of a bell-crank lever and a long rod. One day a gentleman called to make a personal examination of the governor and its manufacture, with a view to investing in the business. I showed him a governor in action on the testing platform, and a woodcut on my circular which represented the governor in its position, as above described, with a short piece of the connecting-rod attached to the lever. He looked at this cut intently for some time, and then, putting his finger on the broken-off end of the little rod, said, “Ah, I see; the steam enters there.” I made no reply, and he was so much pleased with his own penetration that he invested at once.

I know of only one case in which this governor needed the help of a dash-pot or controlling vessel. In the great plate-mill of the Otis Works, in Cleveland, when the enormous mass of steel struck the rolls, the governor dropped sharply to its seat, and jumped as sharply to the upper limit of its action when this mass was shot out. Mr. Wellman, their general manager, suggested to me an elegant arrangement of air-chambers at the top and bottom of a cylinder, which permitted free motion to the governor through its whole range of action, but cushioned it on confined air at the ends.

For several years I made the counterpoise of the governor in the form of a vase. The present form with hemispherical top was suggested by Mr. Whitworth in 1866, and shown by me in the Paris Exposition of 1867. It has three advantages. It ismore readily turned with a circular tool-rest, and it contains more metal and looks more mechanical.

I exhibited the governor in operation at a fair of the American Institute held on Fourteenth Street between Sixth and Seventh avenues, New York City (where the armory of the Twelfth Regiment now stands), making an arrangement with an exhibitor of an engine for that purpose. I remember that Mr. George H. Reynolds, then an engineer in the works of Mr. Delamater at the foot of West Thirteenth Street, as he passed it with a friend a day or two after it was started, remarked in my hearing, “It will take a horse-power to drive that governor.” It would not do to let any such nonsense get around as the opinion of an engineer, so the next morning the governor was driven by a belt ⁵⁄₈ of an inch wide, and continued to be so through the fair. I was sorry afterwards that I did not use a half-inch belt, which would have driven it just as well, and indeed I think even a narrower belt would have done, as the foot of the spindle was of hardened steel, a segment of a sphere, running in a puddle of oil in a hardened step cupped to a larger radius.

The funniest application of the governor I ever made was the following: The Civil War had just broken out, and every Yankee was making some warlike invention. The most ridiculous of all was a centrifugal gun. A company was formed for its manufacture. The shot, about an inch in diameter, was fed in at the center of a swiftly revolving wheel and thrown out through a barrel at the periphery, with a velocity that, it was estimated by the inventor, would carry it about two miles. This velocity was to be got up in about one second. The governor would not act quickly enough, and the engine was stopped. The parties heard of my governor, and ordered one, offering to pay for it in a tempting amount of their stock. I preferred the cash and got it. The governor filled the bill, the shot was delivered, the velocity of revolution not falling sensibly, but we judged by the sharp fall of the counterpoise that it required not less than twenty horse-powers to do it.

The gun was tried on the bank of the Hudson, the Palisades opposite being the target. The inventor declared that every shot hit the mark, but some evil-minded persons insisted that theyfell into the water within a quarter of a mile of the shore from which they were fired.

About the same time the absurdity of sending into the field a tank of water, a boiler, an engine and the gun, on separate wheels, connected by pipes or belting, which would be ruined by the least damage to anything, began to dawn on the enthusiasts, and the thing was abandoned.

I furnished one of my first governors to Mr. James Horner to regulate a rolling-mill near Boonton, N. J., a sale which is worth recording. This mill was employed in rolling steel pretty high in carbon into rods for making gimlets, and the three-high train had not yet issued from the brain of Mr. Fritz. The rolling was slow work. The resistance brought down the speed of the engine before the governor could act, and they could have only one pass in the rolls at a time. The workmen had to carry the end of the rod around and insert it in the next groove after it had run out of the former one. The rod would be black before it was finished, and often it was difficult to get it finished at all. I do not know of any change that so much impressed me at the time as did that which followed the putting of my governor on this engine. The full speed was kept up, the billets seemed to rush through the rolls, two and even three passes could be in them at the same time, and the rods were still at a dull red heat when finished.

This success induced me to make a raid on Pittsburg. I found there very different conditions. They then rolled nothing but iron, so far as I saw or heard. In the first mill I visited, after I had discussed the subject with one of the proprietors, an old man came up to me and said, “Do you see that chair? I have sat in that chair twenty-four years.” The chair corroborated his story. “I watch the rolls; when a bar enters them, I turn on more steam; when it goes out I shut it off. If you put in a governor that will do as well, I shall be discharged. I don’t know how to do anything else; I have a family dependent on me, and I don’t know what I should do.” I did not hesitate long about what I should do. I could not improve on the old man’s action. He regulated the speed perfectly. The only result of my success would be to beggar him. Superseding hand labor by machinery I did not in this particular case care to be responsible for. I concluded thatthe Pittsburg way was good enough for them, and took the next train for home.

The first governor I sold was to Mr. William Moller for his sugar-refinery on Vandam Street. The engine to be regulated was an old-fashioned beam-engine. The governor was to be set on a bracket that we had to bolt to the wall, and a pulley some 3 feet or more in diameter had to be made in halves and put on the shaft. To make sure that no mistake would be made, I went down myself to make a gauge of that shaft. I took a ³⁄₈-inch steel rod bent to span the shaft, and made of this an outside gauge with great care. Now this was not what I wanted, but I did not know it. I wanted an inside gauge, representing the diameter of the shaft, and what I did make was useful only to compare the two.

I returned highly satisfied with my work, leaving the real gauge to be made in the shop, where it could not be compared with the shaft. What might reasonably have been expected to happen did happen. In some unaccountable way something happened to my gauge, and when we went to install the governor we found the pulley had been bored ¹⁄₄ inch too small. We had to work hard all night, and got through only just in time for the engine to start at its usual hour in the morning. If I had sent a man who knew his business to make this gauge I should have avoided a lot of trouble, but I should not have learned anything.

In preparing for the establishment of the governor manufacture I visited the works of Geo. S. Lincoln & Co., in Hartford, and saw twist-drills in use, cutting chips instead of scraping. They attracted my attention and I inquired about them, and was told that they made them themselves. They kindly took me into the smith-shop and had one made for me to witness the operation. The smith heated a round bar of steel and swaged channels in it on opposite sides. They had quite a set of top and bottom swages for different-sized channels. He then took another heat on the bar and twisted it by hand, giving a gradually increasing twist, which at the end was quite rapid. An increasing twist was obtained in this way. The drill was held in a vise, so that only the projecting end of it could receive the amount of twist then being imparted. The drill had to be moved in the vise of course a numberof times. The channels were smoothed out with files, and when the drill was turned in the lathe sharp cutting edges were developed, which needed only to be backed off by grinding. I took one of these drills home with me to serve as a pattern and equipped my shop with them. They were of the highest use to me. The small ones drilled the holes for the governor joints, and the large ones drilled the counterpoise and the column for the governor spindle. I suppose the twist-drill had its origin in these Hartford works.

I never saw any twist-drills in England except at Mr. Whitworth’s, and these I thought were the funniest things I ever did see. They were twisted by the blacksmith out of square bars and with a uniform quick twist, were left rough, and did not fill the hole, and the ends were flattened out in the form of the common drill to scrape, and not to cut.

When I returned from England in 1868 twist-drills were coming into general use in this country. After 1876 the firm of Smith & Coventry introduced them in England.

At that time almost everything in machine-shops was done in the old-fashioned way, and accuracy depended entirely on the skill of the workman. The tool work left much to be done by the fitter. Interchangeability was unknown, even in screw-threads. For example, when nuts were removed from a cylinder head, pains had always to be taken that each nut was replaced on its own bolt, as no two were exactly of a size. This condition developed a class of very skillful all-round workmen; but my earliest observation showed me that in manufacturing it was important that so far as possible the personal factor should be eliminated. I adopted the rule that in mechanical work there was only one way to insure that anything should always be done right, and that was to make it impossible that it should be done wrong. For example, in my governor gears their true running required that the bore should be absolutely correct, both in position and in direction. I had seen many gears bored. They were held in the jaws of a chuck and trued by marking their projecting side when running with a piece of chalk. It was evident that absolute truth could hardly ever be reached in this way, and the approximation to it depended wholly on the skill and pains of the workman.Besides, much time was lost in setting each wheel. These objections were much aggravated in the case of bevel-gears.

I met these difficulties in this way. In standardizing my governors I found it necessary to make eight sizes, but managed to use only three different pairs of gears. I made a separate chuck for each of these six wheels, the faces of which were turned to fit the top and inner ends of the teeth, the same surfaces to which I had seen the chalk applied. When the castings were received from the foundry the first operation on them was to bed them to their chucks, which were covered with a thin coating of red lead for this purpose. The workman was careful to remove only projecting imperfections without touching the true surfaces of the teeth. After this the gears, being held firmly to their chucks by means of a yoke, were bored rapidly and always with absolute truth. Result: their running was practically noiseless.

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 extendedquite 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.

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