DECISIONS ARRIVED AT BY EXPERIENCE.

Experience has decided that the impulse roller should be about half the diameter of the escape wheel, and experience has also decided that an escape wheel of fifteen teeth has the greatest number of advantages; also, that the balance should make 14,400 vibrations in one hour. We will accept these proportions and conditions as best, from the fact that they are now almost universally adopted by our best chronometer makers. Although it would seem as if these proportions should have established themselves earlier among practical men, we shall in these drawings confine ourselves to the graphic plan, considering it preferable. In the practical detail drawing we advise the employment of the scale given, i.e., delineating an escape wheel 10" in diameter. The drawings which accompany the description are one-fourth of this size, for the sake of convenience in copying.

With an escape wheel of fifteen teeth the impulse arc is exactly twenty-four degrees, and of course the periphery of the impulse roller must intersect the periphery of the escape wheel for this arc (24 deg.). The circles A B, Fig. 139, represent the peripheries of these two mobiles, and the problem in hand is to locate and define the position of the two centers a c. These, of course, are not separated, the sum of the two radii, i.e., 5" + 21/2" (in the large drawing), as these circles intersect, as shown at d. Arithmetically considered, the problem is quite difficult, but graphically, simple enough. After we have swept the circle A with a radius of 5", we draw the radial line a f, said line extending beyond the circle A.

LOCATING THE CENTER OF THE BALANCE STAFF.

Somewhere on this line is located the center of the balance staff, and it is the problem in hand to locate or establish this center. Now, it is known the circles which define the peripheries of the escape wheel and the impulse roller intersect at e e^2. We can establish on our circle A where these intersections take place by laying off twelve degrees, one-half of the impulse arc on each side of the line of centers a f on this circle and establishing the points e e^2. These points e e^2 being located at the intersection of the circles A and B, must be at the respective distances of 5" and 21/2" distance from the center of the circles A B; consequently, if we set our dividers at 21/2" and place one leg at e and sweep the short arc g^2, and repeat this process when one leg of the dividers is set at e^2, the intersection of the short arcs g and g^2 will locate the center of our balance staff. We have now our two centers established, whose peripheries are in the relation of 2 to 1.

To know, in the chronometer which we are supposed to be constructing, the exact distance apart at which to plant the hole jewels for our two mobiles, i.e., escape wheel and balance staff, we measure carefully on our drawing the distance from a to c (the latter we having just established) and make our statement in the rule of three, as follows: As (10) the diameter of drawn escape wheel is to our real escape wheel so is the measured distance on our drawing to the real distance in the chronometer we are constructing.

It is well to use great care in the large drawing to obtain great accuracy, and make said large drawing on a sheet of metal. This course is justified by the degree of perfection to which measuring tools have arrived in this day. It will be found on measurement of the arc of the circle B, embraced between the intersections e e^2, that it is about forty-eight degrees. How much of this we can utilize in our escapement will depend very much on the perfection and accuracy of construction.



We show at Fig. 140 three teeth of an escape wheel, together with the locking jewel E and impulse jewel D. Now, while theoretically we could commence the impulse as soon as the impulse jewel D was inside of the circle representing the periphery of the escape wheel, still, in practical construction, we must allow for contingencies. Before it is safe for the escape wheel to attack the impulse jewel, said jewel must be safely inside of said escape wheel periphery, in order that the attacking tooth shall act with certainty and its full effect. A good deal of thought and study can be bestowed to great advantage on the "action" of a chronometer escapement. Let us examine the conditions involved. We show in Fig. 140 the impulse jewel D just passing inside the circle of the periphery of the escape wheel. Now the attendant conditions are these: The escape wheel is locked fast and perfectly dead, and in the effort of unlocking it has to first turn backward against the effort of the mainspring; the power of force required for this effort is derived from the balance in which is stored up, so to speak, power from impulses imparted to the balance by former efforts of the escape wheel. In actual fact, the balance at the time the unlocking takes place is moving with nearly its greatest peripheral velocity and, as stated above, the escape wheel is at rest.

Here comes a very delicate problem as regards setting the unlocking or discharging jewel. Let us first suppose we set the discharging jewel so the locking jewel frees its tooth at the exact instant the impulse jewel is inside the periphery of the escape wheel. As just stated, the escape wheel is not only dead but actually moving back at the time the release takes place. Now, it is evident that the escape wheel requires an appreciable time to move forward and attack the impulse jewel, and during this appreciable time the impulse jewel has been moving forward inside of the arc A A, which represents the periphery of the escape wheel. The proper consideration of this problem is of more importance in chronometer making than we might at first thought have imagined, consequently, we shall dwell upon it at some length.

HOW TO SET THE DISCHARGING JEWEL.



Theoretically, the escape-wheel tooth should encounter the impulse jewel at the time—instant—both are moving with the same velocity. It is evident then that there can be no special rule given for this, i.e., how to set the discharging jewel so it will free the tooth at exactly the proper instant, from the fact that one chronometer train may be much slower in getting to move forward from said train being heavy and clumsy in construction. Let us make an experiment with a real chronometer in illustration of our problem. To do so we remove our balance spring and place the balance in position. If we start the balance revolving in the direction of the arrow y, Fig. 140, it will cause the escapement to be unlocked and the balance to turn rapidly in one direction and with increasing velocity until, in fact, the escape wheel has but very little effect on the impulse jewel; in fact, we could, by applying some outside source of power—like blowing with a blow pipe on the balance—cause the impulse jewel to pass in advance of the escape wheel; that is, the escape-wheel tooth would not be able to catch the impulse jewel during the entire impulse arc. Let us suppose, now, we set our unlocking or discharging jewel in advance, that is, so the escapement is really unlocked a little before the setting parts are in the positions and relations shown in Fig. 141. Under the new conditions the escape wheel would commence to move and get sufficient velocity on it to act on the impulse jewel as soon as it was inside of the periphery of the escape wheel. If the balance was turned slowly now the tooth of the escape wheel would not encounter the impulse jewel at all, but fall into the passing hollow n; but if we give the balance a high velocity, the tooth would again encounter and act upon the jewel in the proper manner. Experienced adjusters of chronometers can tell by listening if the escape-wheel tooth attacks the impulse jewel properly, i.e., when both are moving with similar velocities. The true sound indicating correct action is only given when the balance has its maximum arc of vibration, which should be about 11/4 revolutions, or perform an arc of 225 degrees on each excursion.

Fig. 142 is a side view of Fig. 141 seen in the direction of the arrow y. We have mentioned a chariot to which the detent is attached, but we shall make no attempt to show it in the accompanying drawings, as it really has no relation to the problem in hand; i.e., explaining the action of the chronometer escapement, as the chariot relates entirely to the convenience of setting and adjusting the relation of the second parts. The size, or better, say, the inside diameter of the pipe at C, Fig. 143, which holds the locking jewel, should be about one-third of a tooth space, and the jewel made to fit perfectly. Usually, jewelmakers have a tendency to make this jewel too frail, cutting away the jewel back of the releasing angle (n, Fig. 143) too much.

A GOOD FORM OF LOCKING STONE.

A very practical form for a locking stone is shown in transverse section at Fig. 143. In construction it is a piece of ruby, or, better, sapphire cut to coincide to its axis of crystallization, into first a solid cylinder nicely fitting the pipe C and finished with an after-grinding, cutting away four-tenths of the cylinder, as shown at I, Fig. 143. Here the line m represents the locking face of the jewel and the line o the clearance to free the escaping tooth, the angle at n being about fifty-four degrees. This angle (n) should leave the rounding of the stone intact, that is, the rounding of the angle should be left and not made after the flat faces m o are ground and polished. The circular space at I is filled with an aluminum pin. The sizes shown are of about the right relative proportions; but we feel it well to repeat the statement made previously, to the effect that the detent to a chronometer cannot well be made too light.



The so-called gold spring shown at H, Figs. 141 and 142, should also be as light as is consistent with due strength and can be made of the composite metal used for gold filled goods, as the only real benefit to be derived from employing gold is to avoid the necessity of applying oil to any part of the escapement. If such gold metal is employed, after hammering to obtain the greatest possible elasticity to the spring, the gold is filed away, except where the spring is acted upon by the discharging jewel h. We have previously mentioned the importance of avoiding wide, flat contacts between all acting surfaces, like where the gold spring rests on the horn of the detent at p; also where the detent banks on the banking screw, shown at G, Fig. 142. Under this principle the impact of the face of the discharging jewel with the end of the gold spring should be confined to as small a surface as is consistent with what will not produce abrasive action. The gold spring is shaped as shown at Fig. 142 and loses, in a measure, under the pipe of the locking jewel, a little more than one-half of the pipe below the blade of the detent being cut away, as shown in Fig. 143, where the lines r r show the extent of the part of the pipe which banks against the banking screw G. In this place even, only the curved surface of the outside of the pipe touches the screw G, again avoiding contact of broad surfaces.

We show the gold spring separate at Fig. 144. A slight torsion or twist is given to the gold spring to cause it to bend with a true curvature in the act of allowing the discharging pallet to pass back after unlocking. If the gold spring is filed and stoned to the right flexure, that is, the thinnest point properly placed or, say, located, the gold spring will not continue in contact with the discharging pallet any longer time or through a greater arc than during the process of unlocking. To make this statement better understood, let us suppose the weakest part of the gold spring H is opposite the arrow y, Fig. 141, it will readily be understood the contact of the discharging stone h would continue longer than if the point of greatest (or easiest) flexure was nearer to the pipe C. If the end D^2 of the horn of the detent is as near as it should be to the discharging stone there need be no fear but the escapement will be unlocked. The horn D^2 of the detent should be bent until five degrees of angular motion of the balance will unlock the escape, and the contact of discharging jewel h should be made without engaging friction. This condition can be determined by observing if the jewel seems to slide up (toward the pipe C) on the gold spring after contact. Some adjusters set the jewel J, Figs. 143 and 141, in such a way that the tooth rests close to the base; such adjusters claiming this course has a tendency to avoid cockling or buckling of the detent spring E. Such adjusters also set the impulse jewel slightly oblique, so as to lean on the opposite angle of the tooth. Our advice is to set both stones in places corresponding to the axis of the balance staff, and the escape-wheel mobiles.

THE DETENT SPRING.



It will be noticed we have made the detent spring E pretty wide and extended it well above the blade of the detent. By shaping the detent in this way nearly all the tendency of the spring E to cockle is annulled. We would beg to add to what we said in regard to setting jewels obliquely. We are unable to understand the advantage of wide-faced stones and deep teeth when we do not take advantage of the wide surfaces which we assert are important. We guarantee that with a detent and spring made as we show, there will be no tendency to cockle, or if there is, it will be too feeble to even display itself. Those who have had extended experience with chronometers cannot fail to have noticed a gummy secretion which accumulates on the impulse and discharging stones of a chronometer, although no oil is ever applied to them. We imagine this coating is derived from the oil applied to the pivots, which certainly evaporates, passes into vapor, or the remaining oil could not become gummy. We would advise, when setting jewels (we mean the locking, impulse and discharging jewels), to employ no more shellac than is absolutely necessary, depending chiefly on metallic contact for security.

DETAILS OF CONSTRUCTION.

We will now say a few words about the number of beats to the hour for a box or marine chronometer to make to give the best results. Experience shows that slow but most perfect construction has settled that 14,400, or four vibrations of the balance to a second, as the proper number, the weight of balance, including balance proper and movable weights, to be about 51/2 pennyweights, and the compensating curb about 1-2/10" in diameter. The escape wheel, 55/100" in diameter and recessed so as to be as light as possible, should have sufficient strength to perform its functions properly. The thickness or, more properly, the face extent of the tooth, measured in the direction of the axis of the escape wheel, should be about 1/20". The recessing should extend half way up the radial back of the tooth at t. The curvature of the back of the teeth is produced with the same radii as the impulse roller. To locate the center from which the arc which defines the back of the teeth is swept, we halve the space between the teeth A^2 and a^4 and establish the point n, Fig. 141, and with our dividers set to sweep the circle representing the impulse roller, we sweep an arc passing the point of the tooth A^3 and u, thus locating the center w. From the center k of the escape wheel we sweep a complete circle, a portion of which is represented by the arc w v. For delineating other teeth we set one leg of our dividers to agree with the point of the tooth and the other leg on the circle w v and produce an arc like z u.

ORIGINAL DESIGNING OF THE ESCAPEMENT.

On delineating our chronometer escapement shown at Fig. 141 we have followed no text-book authority, but have drawn it according to such requirements as are essential to obtain the best results. An escapement of any kind is only a machine, and merely requires in its construction a combination of sound mechanical principles. Neither Saunier nor Britten, in their works, give instructions for drawing this escapement which will bear close analysis. It is not our intention, however, to criticise these authors, except we can present better methods and give correct systems.

TANGENTIAL LOCKINGS.

It has been a matter of great contention with makers of chronometer and also lever escapements as to the advantages of "tangential lockings." By this term is meant a locking the same as is shown at C, Fig. 141, and means a detent planted at right angles to a line radial to the escape-wheel axis, said radial line passing through the point of the escape-wheel tooth resting on the locking jewel. In escapements not set tangential, the detent is pushed forward in the direction of the arrow x about half a tooth space. Britten, in his "Hand-Book," gives a drawing of such an escapement. We claim the chief advantage of tangential locking to lie in the action of the escape-wheel teeth, both on the impulse stone and also on the locking stone of the detent. Saunier, in his "Modern Horology," gives the inclination of the front fan of the escape-wheel teeth as being at an angle of twenty-seven degrees to a radial line. Britten says twenty degrees, and also employs a non-tangential locking.

Our drawing is on an angle of twenty-eight degrees, which is as low as is safe, as we shall proceed to demonstrate. For establishing the angle of an escape-wheel tooth we draw the line C d, from the point of the escape-wheel tooth resting on the locking stone shown at C at an angle of twenty-eight degrees to radial line C k. We have already discussed how to locate and plant the center of the balance staff.

We shall not show in this drawing the angular motion of the escape wheel, but delineate at the radial lines c e and c f of the arc of the balance during the extent of its implication with the periphery of the escape wheel, which arc is one of about forty-eight degrees. Of this angle but forty-three degrees is attempted to be utilized for the purpose of impulse, five degrees being allowed for the impulse jewel to pass inside of the arc of periphery of the escape wheel before the locking jewel releases the tooth of the escape wheel resting upon it. At this point it is supposed the escape wheel attacks the impulse jewel, because, as we just explained, the locking jewel has released the tooth engaging it. Now, if the train had no weight, no inertia to overcome, the escape wheel tooth A^2 would move forward and attack the impulse pallet instantly; but, in fact, as we have already explained, there will be an appreciable time elapse before the tooth overtakes the rapidly-moving impulse jewel. It will, of course, be understood that the reference letters used herein refer to the illustrations that have appeared on preceding pages.

If we reason carefully on the matter, we will readily comprehend that we can move the locking jewel, i.e., set it so the unlocking will take place in reality before the impulse jewel has passed through the entire five degrees of arc embraced between the radial lines c e and c g, Fig. 141, and yet have the tooth attack the jewel after the five degrees of arc. In practice it is safe to set the discharging jewel h so the release of the held tooth A^1 will take place as soon as the tooth A^2 is inside the principal line of the escape wheel. As we previously explained, the contact between A^2 and the impulse jewel i would not in reality occur until the said jewel i had fully passed through the arc (five degrees) embraced between the radial lines c e and c g.

At this point we will explain why we drew the front fan of the escape-wheel teeth at the angle of twenty-eight degrees. If the fan of impulse jewel i is set radial to the axis of the balance, the engagement of the tooth A^2 would be at a disadvantage if it took place prior to this jewel passing through an arc of five degrees inside the periphery of the escape wheel. It will be evident on thought that if an escape-wheel tooth engaged the impulse stone before the five-degrees angle had passed, the contact would not be on its flat face, but the tooth would strike the impulse jewel on its outer angle. A continued inspection will also reveal the fact that in order to have the point of the tooth engage the flat surface of the impulse pallet the impulse jewel must coincide with the radial line c g. If we seek to remedy this condition by setting the impulse jewel so the face is not radial, but inclined backward, we encounter a bad engaging friction, because, during the first part of the impulse action, the tooth has to slide up the face of the impulse jewel. All things considered, the best action is obtained with the impulse jewel set so the acting face is radial to the balance staff and the engagement takes place between the tooth and the impulse jewel when both are moving with equal velocities, i.e., when the balance is performing with an arc (or motion) of 11/4 revolutions or 225 degrees each way from a point of rest. Under such conditions the actual contact will not take place before some little time after the impulse jewel has passed the five-degree arc between the lines c e and c g.

THE DROP AND DRAW CONSIDERED.

Exactly how much drop must be allowed from the time the tooth leaves the impulse jewel before the locking tooth engages the locking jewel will depend in a great measure on the perfection of workmanship, but should in no instance be more than what is absolutely required to make the escapement safe. The amount of draw given to the locking stone c is usually about twelve degrees to the radial line k a. Much of the perfection of the chronometer escapement will always depend on the skill of the escapement adjuster and not on the mechanical perfection of the parts.

The jewels all have to be set by hand after they are made, and the distance to which the impulse jewel protrudes beyond the periphery of the impulse roller is entirely a matter for hand and eye, but should never exceed 2/1000". After the locking jewel c is set, we can set the foot F of the detent D forward or back, to perfect and correct the engagement of the escape-wheel teeth with the impulse roller B. If we set this too far forward, the tooth A^3 will encounter the roller while the tooth A^2 will be free.

We would beg to say here there is no escape wheel made which requires the same extreme accuracy as the chronometer, as the tooth spaces and the equal radial extent of each tooth should be only limited by our powers toward perfection. It is usual to give the detent a locking of about two degrees; that is, it requires about two degrees to open it, counting the center of fluxion of the detent spring E and five degrees of balance arc.

FITTING UP OF THE FOOT.

Several attempts have been made by chronometer makers to have the foot F adjustable; that is, so it could be moved back and forth with a screw, but we have never known of anything satisfactory being accomplished in this direction. About the best way of fitting up the foot F seems to be to provide it with two soft iron steady pins (shown at j) with corresponding holes in the chariot, said holes being conically enlarged so they (the pins) can be bent and manipulated so the detent not only stands in the proper position as regards the escape wheel, but also to give the detent spring E the proper elastic force to return in time to afford a secure locking to the arresting tooth of the escape wheel after an impulse has been given.

If these pins j are bent properly by the adjuster, whoever afterwards cleans the chronometer needs only to gently push the foot F forward so as to cause the pins j to take the correct positions as determined by the adjuster and set the screw l up to hold the foot F when all the other relations are as they should be, except such as we can control by the screw G, which prevents the locking jewel from entering too deeply into the escape wheel.

In addition to being a complete master of the technical part of his business, it is also desirable that the up-to-date workman should be familiar with the subject from a historical point of view. To aid in such an understanding of the matter we have translated from "L'Almanach de l'Horologerie et de la Bijouterie" the matter contained in the following chapter.



CHAPTER IV.

HISTORY OF ESCAPEMENTS.

It could not have been long after man first became cognizant of his reasoning faculties that he began to take more or less notice of the flight of time. The motion of the sun by day and of the moon and stars by night served to warn him of the recurring periods of light and darkness. By noting the position of these stellar bodies during his lonely vigils, he soon became proficient in roughly dividing up the cycle into sections, which he denominated the hours of the day and of the night. Primitive at first, his methods were simple, his needs few and his time abundant. Increase in numbers, multiplicity of duties, and division of occupation began to make it imperative that a more systematic following of these occupations should be instituted, and with this end in view he contrived, by means of burning lights or by restricting the flowing of water or the falling of weights, to subdivide into convenient intervals and in a tolerably satisfactory manner the periods of light.

These modest means then were the first steps toward the exact subdivisions of time which we now enjoy. Unrest, progress, discontent with things that be, we must acknowledge, have, from the appearance of the first clock to the present hour, been the powers which have driven on the inventive genius of watch and clockmakers to designate some new and more acceptable system for regulating the course of the movement. In consequence of this restless search after the best, a very considerable number of escapements have been invented and made up, both for clocks and watches; only a few, however, of the almost numberless systems have survived the test of time and been adopted in the manufacture of the timepiece as we know it now. Indeed, many such inventions never passed the experimental stage, and yet it would be very interesting to the professional horologist, the apprentice and even the layman to become more intimately acquainted with the vast variety of inventions made upon this domain since the inception of horological science. Undoubtedly, a complete collection of all the escapements invented would constitute a most instructive work for the progressive watchmaker, and while we are waiting for a competent author to take such an exhaustive work upon his hands, we shall endeavor to open the way and trust that a number of voluntary collaborators will come forward and assist us to the extent of their ability in filling up the chinks.

PROBLEMS TO BE SOLVED.

The problem to be solved by means of the escapement has always been to govern, within limits precise and perfectly regular, if it be possible, the flow of the motive force; that means the procession of the wheel-work and, as a consequence, of the hands thereto attached. At first blush it seems as if a continually-moving governor, such as is in use on steam engines, for example, ought to fulfil the conditions, and attempts have accordingly been made upon this line with results which have proven entirely unsatisfactory.

Having thoroughly sifted the many varieties at hand, it has been finally determined that the only means known to provide the most regular flow of power consists in intermittently interrupting the procession of the wheel-work, and thereby gaining a periodically uniform movement. Whatever may be the system or kind of escapement employed, the functioning of the mechanism is characterized by the suspension, at regular intervals, of the rotation of the last wheel of the train and in transmitting to a regulator, be it a balance or a pendulum, the power sent into that wheel.

ESCAPEMENT THE MOST ESSENTIAL PART.

Of all the parts of the timepiece the escapement is then the most essential; it is the part which assures regularity in the running of the watch or clock, and that part of parts that endows the piece with real value. The most perfect escapement would be that one which should perform its duty with the least influence upon the time of oscillation or vibration of the regulating organ. The stoppage of the train by the escapement is brought about in different ways, which may be gathered under three heads or categories. In the two which we shall mention first, the stop is effected directly upon the axis of the regulator, or against a piece which forms a part of that axis; the tooth of the escape wheel at the moment of its disengagement remains supported upon or against that stop.

In the first escapement invented and, indeed, in some actually employed to-day for certain kinds of timekeepers, we notice during the locking a retrograde movement of the escape wheel; to this kind of movement has been given the name of recoil escapement. It was recognized by the fraternity that this recoil was prejudicial to the regularity of the running of the mechanism and, after the invention of the pendulum and the spiral, inventive makers succeeded in replacing this sort of escapement with one which we now call the dead-beat escapement. In this latter the wheel, stopped by the axis of the regulator, remains immovable up to the instant of its disengagement or unlocking.

In the third category have been collected all those forms of escapement wherein the escape wheel is locked by an intermediate piece, independent of the regulating organ. This latter performs its vibrations of oscillation quite without interference, and it is only in contact with the train during the very brief moment of impulse which is needful to keep the regulating organ in motion. This category constitutes what is known as the detached escapement class.

Of the recoil escapement the principal types are: the verge escapement or crown-wheel escapement for both watches and clocks, and the recoil anchor escapement for clocks. The cylinder and duplex escapements for watches and the Graham anchor escapement for clocks are styles of the dead-beat escapement most often employed. Among the detached escapements we have the lever and detent or chronometer escapements for watches; for clocks there is no fixed type of detached lever and it finds no application to-day.

THE VERGE ESCAPEMENT.

The verge escapement, called also the crown-wheel escapement, is by far the simplest and presents the least difficulty in construction. We regret that the world does not know either the name of its originator nor the date at which the invention made its first appearance, but it seems to have followed very closely upon the birth of mechanical horology.

Up to 1750 it was employed to the exclusion of almost all the others. In 1850 a very large part of the ordinary commercial watches were still fitted with the verge escapement, and it is still used under the form of recoil anchor in clocks, eighty years after the invention of the cylinder escapement, or in 1802. Ferdinand Berthoud, in his "History of the Measurement of Time," says of the balance-wheel escapement: "Since the epoch of its invention an infinite variety of escapements have been constructed, but the one which is employed in ordinary watches for every-day use is still the best." In referring to our illustrations, we beg first to call attention to the plates marked Figs. 145 and 146. This plate gives us two views of a verge escapement; that is, a balance wheel and a verge formed by its two opposite pallets. The views are intentionally presented in this manner to show that the verge V may be disposed either horizontally, as in Fig. 146, or vertically, as in Fig. 145.



Let us imagine that our drawing is in motion, then will the tooth d, of the crown wheel R, be pushing against the pallet P, and just upon the point of slipping by or escaping, while the opposite tooth e is just about to impinge upon the advancing pallet P'. This it does, and will at first, through the impulse received from the tooth d be forced back by the momentum of the pallet, that is, suffer a recoil; but on the return journey of the pallet P', the tooth e will then add its impulse to the receding pallet. The tooth e having thus accomplished its mission, will now slip by and the tooth c will come in lock with the pallet P and, after the manner just described for e, continue the escapement. Usually these escape wheels are provided with teeth to the number of 11, 13 or 15, and always uneven. A great advantage possessed by this form of escapement is that it does not require any oil, and it may be made to work even under very inferior construction.

OLDEST ARRANGEMENT OF A CROWN-WHEEL ESCAPEMENT.



Plate 147 shows us the oldest known arrangement of a crown-wheel escapement in a clock. R is the crown wheel or balance wheel acting upon the pallets P and P', which form part of the verge V. This verge is suspended as lightly as possible upon a pliable cord C and carries at its upper end two arms, B and B, called adjusters, forming the balance. Two small weights D D, adapted to movement along the rules or adjusters serve to regulate the duration of a vibration. In Fig. 148 we have the arrangement adopted in small timepieces and watches: B represents the regulator in the form of a circular balance, but not yet furnished with a spiral regulating spring; c is the last wheel of the train and called the fourth wheel, it being that number distant from the great wheel. As will be seen, the verge provided with its pallets is vertically placed, as in the preceding plate.



Here it will quickly be seen that regarded from the standpoint of regularity of motion, this arrangement can be productive of but meager results. Subjected as it is to the influence of the slightest variation in the motive power and of the least jar or shaking, a balance wheel escapement improvided with a regulator containing within itself a regulating force, could not possibly give forth anything else than an unsteady movement. However, mechanical clocks fitted with this escapement offer indisputable advantages over the ancient clepsydra; in spite of their imperfections they rendered important services, especially after the striking movement had been added. For more than three centuries both this crude escapement and the cruder regulator were suffered to continue in this state without a thought of improvement; even in 1600, when Galileo discovered the law governing the oscillation of the pendulum, they did not suspect how important this discovery was for the science of time measurement.

GALILEO'S EXPERIMENTS.



Galileo, himself, in spite of his genius for investigation, was so engrossed in his researches that he could not seem to disengage the simple pendulum from the compound pendulums to which he devoted his attention; besides, he attributed to the oscillation an absolute generality of isochronism, which they did not possess; nor did he know how to apply his famous discovery to the measurement of time. In fact, it was not till after more than half a century had elapsed, in 1657, to be exact, that the celebrated Dutch mathematician and astronomer, Huygens, published his memoirs in which he made known to the world the degree of perfection which would accrue to clocks if the pendulum were adopted to regulate their movement.



An attempt was indeed made to snatch from Huygens and confer upon Galileo the glory of having first applied the pendulum to a clock, but this attempt not having been made until some time after the publication of "Huygens' Memoirs," it was impossible to place any faith in the contention. If Galileo had indeed solved the beautiful problem, both in the conception and the fact, the honor of the discovery was lost to him by the laziness and negligence of his pupil, Viviani, upon whom he had placed such high hopes. One thing is certain, that the right of priority of the discovery and the recognition of the entire world has been incontestably bestowed upon Huygens. The escapement which Galileo is supposed to have conceived and to which he applied the pendulum, is shown in Fig. 149. The wheel R is supplied with teeth, which lock against the piece D attached to a lever pivoted at a, and also with pins calculated to impart impulses to the pendulum through the pallet P. The arm L serves to disengage or unlock the wheel by lifting the lever D upon the return oscillation of the pendulum.



A careful study of Fig. 150 will discover a simple transposition which it became necessary to make in the clocks, for the effectual adaptation of the pendulum to their regulation. The verge V was set up horizontally and the pendulum B, suspended freely from a flexible cord, received the impulses through the intermediation of the forked arm F, which formed a part of the verge. At first this forked arm was not thought of, for the pendulum itself formed a part of the verge. A far-reaching step had been taken, but it soon became apparent that perfection was still a long way off. The crown-wheel escapement forcibly incited the pendulum to wider oscillations; these oscillations not being as Galileo had believed, of unvaried durations, but they varied sensibly with the intensity of the motive power.

THE ATTAINMENT OF ISOCHRONISM BY HUYGENS.

Huygens rendered his pendulum isochronous; that is, compelled it to make its oscillations of equal duration, whatever might be the arc described, by suspending the pendulum between two metallic curves c c', each one formed by an arc of a cycloid and against which the suspending cord must lie upon each forward or backward oscillation. We show this device in Fig. 151. In great oscillations, and by that we mean oscillations under a greater impulse, the pendulum would thus be shortened and the shortening would correct the time of the oscillation. However, the application of an exact cycloidal arc was a matter of no little difficulty, if not an impossibility in practice, and practical men began to grope about in search of an escapement which would permit the use of shorter arcs of oscillation. At London the horologist, G. Clement, solved the problem in 1675 with his rack escapement and recoil anchor. In the interval other means were invented, especially the addition of a second pendulum to correct the irregularities of the first. Such an escapement is pictured in Fig. 152. The verge is again vertical and carries near its upper end two arms D D, which are each connected by a cord with a pendulum. The two pendulums oscillate constantly in the inverse sense the one to the other.



ANOTHER TWO-PENDULUM ESCAPEMENT.

We show another escapement with two pendulums in Fig. 153. These are fixed directly upon two axes, each one carrying a pallet P P' and a segment of a toothed wheel D D, which produces the effect of solidarity between them. The two pendulums oscillate inversely one to the other, and one after the other receives an impulse. This escapement was constructed by Jean Baptiste Dutertre, of Paris.

Fig. 154 shows another disposition of a double pendulum. While the pendulum here is double, it has but one bob; it receives the impulse by means of a double fork F. C C represents the cycloidal curves and are placed with a view of correcting the inequality in the duration of the oscillations. In watches the circular balances did not afford any better results than the regulating rods or rules of the clocks, and the pendulum, of course, was out of the question altogether; it therefore became imperative to invent some other regulating system.



It occured to the Abbe d'Hautefeuille to form a sort of resilient mechanism by attaching one end of a hog's bristle to the plate and the other to the balance near the axis. Though imperfect in results, this was nevertheless a brilliant idea, and it was but a short step to replace the bristle with a straight and very flexible spring, which later was supplanted by one coiled up like a serpent; but in spite of this advancement, the watches did not keep much better time. Harrison, the celebrated English horologist, had recourse to two artifices, of which the one consisted in giving to the pallets of the escapement such a curvature that the balance could be led back with a velocity corresponding to the extension of the oscillation; the second consisted of an accessory piece, the resultant action of which was analogous to that of the cycloidal curves in connection with the pendulum.

CORRECTING IRREGULARITIES IN THE VERGE ESCAPEMENT.

Huygens attempted to correct these irregularities in the verge escapement in watches by amplifying the arc of oscillation of the balance itself. He constructed for that purpose a pirouette escapement shown in Fig. 155, in which a toothed wheel A adjusted upon the verge V serves as an intermediary between that and the balance B, upon the axis of which was fixed a pinion D. By this method he obtained extended arcs of vibration, but the vibrations were, as a consequence, very slow, and they still remained subject to all the irregularities arising from the variation in the motive power as well as from shocks. A little later, but about the same epoch, a certain Dr. Hook, of the Royal Society of London, contrived another arrangement by means of which he succeeded, so it appeared to him at least, in greatly diminishing the influence of shock upon the escapement; but many other, perhaps greater, inconveniences caused his invention to be speedily rejected. We shall give our readers an idea of what Dr. Hook's escapement was like.



On looking at Fig. 156 we see the escape wheel R, which was flat and in the form of a ratchet; it was provided with two balances. B B engaging each other in teeth, each one carrying a pallet P P' upon its axis; the axes of the three wheels being parallel. Now, in our drawing, the tooth a of the escape wheel exerts its lift upon the pallet P'; when this tooth escapes the tooth b will fall upon the pallet P' on the opposite side, a recoil will be produced upon the action of the two united balances, then the tooth b will give its impulse in the contrary direction. Considerable analogy exists between this form of escapement and that shown in Fig. 153 and intended for clocks. This was the busy era in the watchmaker's line. All the great heads were pondering upon the subject and everyone was on the qui vive for the newest thing in the art.

In 1674 Huygens brought out the first watch having a regulating spring in the form of a spiral; the merit of this invention was disputed by the English savant, Dr. Hook, who pretended, as did Galileo, in the application of the pendulum, to have priority in the idea. Huygens, who had discovered and corrected the irregularities in the oscillations of the pendulum, did not think of those of the balance with the spiral spring. And it was not until the close of the year 1750 that Pierre Le Roy and Ferdinand Berthoud studied the conditions of isochronism pertaining to the spiral.

AN INVENTION THAT CREATED MUCH ENTHUSIASM.

However that may be, this magnificent invention, like the adaptation of the pendulum, was welcomed with general enthusiasm throughout the scientific world: without spiral and without pendulum, no other escapement but the recoil escapement was possible; a new highway was thus opened to the searchers. The water clocks (clepsydrae) and the hour glasses disappeared completely, and the timepieces which had till then only marked the hours, having been perfected up to the point of keeping more exact time, were graced with the addition of another hand to tell off the minutes.



It was not until 1695 that the first dead-beat escapement appeared upon the scene; during the interval of over twenty years all thought had been directed toward the one goal, viz.: the perfecting of the verge escapement; but practice demonstrated that no other arrangement of the parts was superior to the original idea. For the benefit of our readers we shall give a few of these attempts at betterment, and you may see for yourselves wherein the trials failed.

Fig. 157 represents a verge escapement with a ratchet wheel, the pallets P P' being carried upon separate axes. The two axes are rigidly connected, the one to the other, by means of the arms o o'. One of the axes carries besides the fork F, which transmits the impulse to the pendulum B. In the front view, at the right of the plate, for the sake of clearness the fork and the pendulum are not shown, but one may easily see the jointure of the arms o o' and their mode of operation.

Another very peculiar arrangement of the verge escapement we show at Fig. 158. In this there are two wheels, one, R', a small one in the form of a ratchet; the other, R, somewhat larger, called the balance wheel, but being supplied with straight and slender teeth. The verge V carrying the two pallets is pivoted in the vertical diameter of the larger wheel. The front view shows the modus operandi of this combination, which is practically the same as the others. The tooth a of the large wheel exerts its force upon the pallet P, and the tooth b of the ratchet will encounter the pallet P'. This pallet, after suffering its recoil, will receive the impulse communicated by the tooth b. This escapement surely could not have given much satisfaction, for it offers no advantage over the others, besides it is of very difficult construction.



INGENIOUS ATTEMPTS AT SOLUTION OF A DIFFICULT PROBLEM.

Much ingenuity to a worthy end, but of little practical value, is displayed in these various attempts at the solution of a very difficult problem. In Fig. 159 we have a mechanism combining two escape wheels engaging each other in gear; of the two wheels, R R', one alone is driven directly by the train, the other being turned in the opposite direction by its comrade. Both are furnished with pins c c', which act alternately upon the pallets P P' disposed in the same plane upon the verge V and pivoted between the wheels. Our drawing represents the escapement at the moment when the pin C' delivers its impulse, and this having been accomplished, the locking takes place upon the pin C of the other wheel upon the pallet P'. Another system of two escape wheels is shown in Fig. 160, but in this case the two wheels R R are driven in a like direction by the last wheel A of the train. The operation of the escapement is the same as in Fig. 159.



In Fig. 161 we have a departure from the road ordinarily pursued. Here we see an escapement combining two levers, invented by the Chevalier de Bethune and applied by M. Thiout, master-horologist, at Paris in 1727. P P' are the two levers or pallets separately pivoted. Upon the axis V, of the lever P, is fixed a fork which communicates the motion to the pendulum. The two levers are intimately connected by the two arms B B', of which the former carries an adjusting screw, a well-conceived addition for regulating the opening between the pallets. The counter-weight C compels constant contact between the arms B B'. The function is always the same, the recoil and the impulsion operate upon the two pallets simultaneously. This escapement enjoyed a certain degree of success, having been employed by a number of horologists who modified it in various ways.

VARIOUS MODIFICATIONS

Some of these modifications we shall show. For the first example, then, let Fig. 162 illustrate. In this arrangement the fork is carried upon the axis of the pallet P', which effectually does away with the counter-weight C, as shown. Somewhat more complicated, but of the same intrinsic nature, is the arrangement displayed in Fig. 163. We should not imagine that it enjoyed a very extensive application. Here the two levers are completely independent of each other; they act upon the piece B B upon the axis V of the fork. The counter-weights C C' maintain the arms carrying the rollers D D' in contact with the piece B B' which thus receives the impulse from the wheel R. Two adjusting screws serve to place the escapement upon the center. By degrees these fantastic constructions were abandoned to make way for the anchor recoil escapement, which was invented, as we have said, in 1675, by G. Clement, a horologist, of London. In Fig. 164 we have the disposition of the parts as first arranged by this artist. Here the pallets are replaced by the inclines A and B of the anchor, which is pivoted at V upon an axis to which is fixed also the fork. The tooth a escapes from the incline or lever A, and the tooth b immediately rests upon the lever B; by the action of the pendulum the escape wheel suffers a recoil as in the pallet escapement, and on the return of the pendulum the tooth c gives out its impulse in the contrary direction. With this new system it became possible to increase the weight of the bob and at the same time lessen the effective motor power. The travel of the pendulum, or arc of oscillation, being reduced in a marked degree, an accuracy of rate was obtained far superior to that of the crown-wheel escapement. However, this new application of the recoil escapement was not adopted in France until 1695.



The travel of the pendulum, though greatly reduced, still surpassed in breadth the arc in which it is isochronous, and repeated efforts were made to give such shape to the levers as would compel its oscillation within the arc of equal time; a motion which is, as was recognized even at that epoch, the prime requisite to a precise rating. Thus, in 1720, Julien Leroy occupied himself working out the proper shapes for the inclines to produce this desired isochronism. Searching along the same path, Ferd. Berthoud constructed an escapement represented by the Fig. 165. In it we see the same inclines A B of the former construction, but the locking is effected against the slides C and D, the curved faces of which produce isochronous oscillations of the pendulum. The tooth b imparts its lift and the tooth c will lock against the face C; after having passed through its recoil motion this tooth c will butt against the incline A and work out its lift or impulse upon it.

THE GABLE ESCAPEMENT.



The gable escapement, shown in Fig. 166, allows the use of a heavier pendulum, at the same time the anchor embraces within its jaws a greater number of the escape-wheel teeth; an arrangement after this manner leads to the conclusion that with these long levers of the anchor the friction will be considerably increased and the recoil faces will, as a consequence, be quickly worn away. Without doubt, this was invented to permit of opening and closing the contact points of the anchor more easily. Under the name of the English recoil anchor there came into use an escapement with a reduced gable, which embraced fewer teeth between the pallets or inclines; we give a representation of this in Fig. 167. This system seems to have been moderately successful. The anchor recoil escapement in use in Germany to-day is demonstrated in Fig. 168; this arrangement is also found in the American clocks. As we see, the anchor is composed of a single piece of curved steel bent to the desired curves. Clocks provided with this escapement keep reasonably good time; the resistance of the recoils compensate in a measure for the want of isochronism in the oscillations of the pendulum. Ordinary clocks require considerably more power to drive them than finer clocks and, as a consequence, their ticking is very noisy. Several means have been employed to dampen this noise, one of which we show in Fig. 169.



Here the anchor is composed of two pieces, A B, screwed upon a plate H pivoting at V. In their arrangement the two pieces represent, as to distance and curvature, the counterpart of Fig. 168. At the moment of impact their extreme ends recoil or spring back from the shock of the escape teeth, but the resiliency of the metal is calculated to be strong enough to return them immediately to the contact studs e e.

As a termination to this chapter, we shall mention the use made at the present day of the recoil lever escapement in repeating watches. We give a diagram of this construction in Fig. 170. The lever here is intended to restrain and regulate the motion of the small striking work. It is pivoted at V and is capable of a very rapid oscillatory motion, the arc of which may, however, be fixed by the stud or stop D, which limits the swing of the fly C. This fly is of one piece with the lever and, together with the stud D, determines the angular motion of the lever. If the angle be large that means the path of the fly be long, then the striking train will move slowly; but if the teeth of the escape wheel R can just pass by without causing the lever to describe a supplementary or extended arc, the striking work will run off rapidly.



CHAPTER V.

PUTTING IN A NEW CYLINDER.

Putting in a new cylinder is something most watchmakers fancy they can do, and do well; but still it is a job very few workmen can do and fulfill all the requirements a job of this kind demands under the ever-varying conditions and circumstances presented in repairs of this kind. It is well to explain somewhat at this point: Suppose we have five watches taken in with broken cylinders. Out of this number probably two could be pivoted to advantage and make the watches as good as ever. As to the pivoting of a cylinder, we will deal with this later on. The first thing to do is to make an examination of the cylinder, not only to see if it is broken, but also to determine if pivoting is going to bring it out all right. Let us imagine that some workman has, at some previous time, put in a new cylinder, and instead of putting in one of the proper size he has put one in too large or too small. Now, in either case he would have to remove a portion of the escape-wheel tooth, that is, shorten the tooth: because, if the cylinder was too large it would not go in between the teeth, and consequently the teeth would have to be cut or stoned away. If the cylinder was too small, again the teeth would have to be cut away to allow them to enter the cylinder. All workmen have traditions, rules some call them, that they go by in relation to the right way to dress a cylinder tooth; some insisting that the toe or point of the tooth is the only place which should be tampered with. Other workmen insist that the heel of the tooth is the proper place. Now, with all due consideration, we would say that in ninety-nine cases out of a hundred the proper thing to do is to let the escape-wheel teeth entirely alone. As we can understand, after a moment's thought, that it is impossible to have the teeth of the escape wheel too long and have the watch run at all; hence, the idea of stoning a cylinder escape-wheel tooth should not be tolerated.

ESCAPE-WHEEL TEETH vs. CYLINDER.

It will not do, however, to accept, and take it for granted that the escape-wheel teeth are all right, because in many instances they have been stoned away and made too short; but if we accept this condition as being the case, that is, that the escape-wheel teeth are too short, what is the workman going to do about it? The owner of the watch will not pay for a new escape wheel as well as a new cylinder. The situation can be summed up about in this way, that we will have to make the best we can out of a bad job, and pick out and fit a cylinder on a compromise idea.

In regard to picking out a new cylinder, it may not do to select one of the same size as the old one, from the fact that the old one may not have been of the proper size for the escape wheel, because, even in new, cheap watches, the workmen who "run in" the escapement knew very well the cylinder and escape wheel were not adapted for each other, but they were the best he had. Chapter II, on the cylinder escapement, will enable our readers to master the subject and hence be better able to judge of allowances to be made in order to permit imperfect material to be used.

In illustration, let us imagine that we have to put in a new cylinder, and we have none of precisely the proper size, but we have them both a mere trifle too large and too small, and the question is which to use. Our advice is to use the smaller one if it does not require the escape-wheel teeth to be "dressed," that is, made smaller. Why we make this choice is based on the fact that the smaller cylinder shell gives less friction, and the loss from "drop"—that is, side play between the escape-wheel teeth and the cylinder—will be the same in both instances except to change the lost motion from inside to outside drop.

In devising a system to be applied to selecting a new cylinder, we meet the same troubles encountered throughout all watchmakers' repair work, and chief among these are good and convenient measuring tools. But even with perfect measuring tools we would have to exercise good judgment, as just explained. In Chapter II we gave a rule for determining the outside diameter of a cylinder from the diameter of the escape wheel; but such rules and tables will, in nine instances out of ten, have to be modified by attendant circumstances—as, for instance, the thickness of the shell of the cylinder, which should be one-tenth of the outer diameter of the shell, but the shell is usually thicker. A tolerably safe practical rule and one also depending very much on the workman's good judgment is, when the escape-wheel teeth have been shortened, to select a cylinder giving ample clearance inside the shell to the tooth, but by no means large enough to fill the space between the teeth. After studying carefully the instructions just given we think the workman will have no difficulty in selecting a cylinder of the right diameter.

MEASURING THE HEIGHTS.

The next thing is to get the proper heights. This is much more easily arrived at: the main measurement being to have the teeth of the escape wheel clear the upper face of the lower plug. In order to talk intelligently we will make a drawing of a cylinder and agree on the proper names for the several parts to be used in this chapter. Such drawing is shown at Fig. 171. The names are: The hollow cylinder, made up of the parts A A' A'' A''', called the shell—A is the great shell, A' the half shell, A'' the banking slot, and A''' the small shell. The brass part D is called the collet and consists of three parts—the hairspring seat D, the balance seat D' and the shoulder D'', against which the balance is riveted.



The first measurement for fitting a new cylinder is to determine the height of the lower plug face, which corresponds to the line x x, Fig. 171. The height of this face is such as to permit the escape wheel to pass freely over it. In selecting a new cylinder it is well to choose one which is as wide at the banking slot A'' as is consistent with safety. The width of the banking slot is represented by the dotted lines x u. The dotted line v represents the length to which the lower pivot y is to be cut.



There are several little tools on the market used for making the necessary measurements, but we will describe a very simple one which can readily be made. To do so, take about a No. 5 sewing needle and, after annealing, cut a screw thread on it, as shown at Fig, 172, where E represents the needle and t t the screw cut upon it. After the screw is cut, the needle is again hardened and tempered to a spring temper and a long, thin pivot turned upon it. The needle is now shaped as shown at Fig. 173. The pivot at s should be small enough to go easily through the smallest hole jewel to be found in cylinder watches, and should be about 1/16" long. The part at r should be about 3/16" long and only reduced in size enough to fully remove the screw threads shown at t.



We next provide a sleeve or guard for our gage. To do this we take a piece of hard brass bushing wire about 1/2" long and, placing it in a wire chuck, center and drill it nearly the entire length, leaving, say, 1/10" at one end to be carried through with a small drill. We show at F, Fig. 174, a magnified longitudinal section of such a sleeve. The piece F is drilled from the end l up to the line q with a drill of such a size that a female screw can be cut in it to fit the screw on the needle, and F is tapped out to fit such a screw from l up to the dotted line p. The sleeve F is run on the screw t and now appears as shown at Fig. 175, with the addition of a handle shown at G G'. It is evident that we can allow the pivot s to protrude from the sleeve F any portion of its length, and regulate such protrusion by the screw t. To employ this tool for getting the proper length to which to cut the pivot y, Fig. 171, we remove the lower cap jewel to the cylinder pivot and, holding, the movement in the left hand, pass the pivot s, Fig. 175, up through the hole jewel, regulate the length by turning the sleeve F until the arm of the escape wheel I, Fig. 176, will just turn free over it. Now the length of the pivot s, which protrudes beyond the sleeve F, coincides with the length to which we must cut the pivot y, Fig. 171. To hold a cylinder for reducing the length of the pivot y, we hold said pivot in a pair of thin-edged cutting pliers, as shown at Fig. 177, where N N' represent the jaws of a pair of cutting pliers and y the pivot to be cut. The measurement is made by putting the pivot s between the jaws N N' as they hold the pivot. The cutting is done by simply filing back the pivot until of the right length.

TURNING THE PIVOTS.

We have now the pivot y of the proper length, and what remains to be done is to turn it to the right size. We do not think it advisable to try to use a split chuck, although we have seen workmen drive the shell A A''' out of the collet D and then turn up the pivots y z in said wire chuck. To our judgment there is but one chuck for turning pivots, and this is the cement chuck provided with all American lathes. Many workmen object to a cement chuck, but we think no man should lay claim to the name of watchmaker until he masters the mystery of the cement chuck. It is not such a very difficult matter, and the skill once acquired would not be parted with cheaply. One thing has served to put the wax or cement chuck into disfavor, and that is the abominable stuff sold by some material houses for lathe cement. The original cement, made and patented by James Bottum for his cement chuck, was made up of a rather complicated mixture; but all the substances really demanded in such cement are ultramarine blue and a good quality of shellac. These ingredients are compounded in the proportion of 8 parts of shellac and 1 part of ultramarine—all by weight.

HOW TO USE A CEMENT CHUCK.

The shellac is melted in an iron vessel, and the ultramarine added and stirred to incorporate the parts. Care should be observed not to burn the shellac. While warm, the melted mass is poured on to a cold slab of iron or stone, and while plastic made into sticks about 1/2" in diameter.



We show at Fig. 178 a side view of the outer end of a cement chuck with a cylinder in position. We commence to turn the lower pivot of a cylinder, allowing the pivot z to rest at the apex of the hollow cone a, as shown. There is something of a trick in turning such a hollow cone and leaving no "tit" or protuberance in the center, but it is important it should be done. A little practice will soon enable one to master the job. A graver for this purpose should be cut to rather an oblique point, as shown at L, Fig. 179. The slope of the sides to the recess a, Fig. 178, should be to about forty-five degrees, making the angle at a about ninety degrees. The only way to insure perfect accuracy of centering of a cylinder in a cement chuck is center by the shell, which is done by cutting a piece of pegwood to a wedge shape and letting it rest on the T-rest; then hold the edge of the pegwood to the cylinder as the lathe revolves and the cement soft and plastic. A cylinder so centered will be absolutely true. The outline curve at c, Fig. 178, represents the surface of the cement.

The next operation is turning the pivot to the proper size to fit the jewel. This is usually done by trial, that is, trying the pivot into the hole in the jewel. A quicker way is to gage the hole jewel and then turn the pivot to the right size, as measured by micrometer calipers. In some cylinder watches the end stone stands at some distance from the outer surface of the hole jewel; consequently, if the measurement for the length of the pivot is taken by the tool shown at Fig. 175, the pivot will apparently be too short. When the lower end stone is removed we should take note if any allowance is to be made for such extra space. The trouble which would ensue from not providing for such extra end shake would be that the lower edge of the half shell, shown at e, Fig. 171, would strike the projection on which the "stalk" of the tooth is planted. After the lower pivot is turned to fit the jewel the cylinder is to be removed from the cement chuck and the upper part turned. The measurements to be looked to now are, first, the entire length of the cylinder, which is understood to be the entire distance between the inner faces of the two end stones, and corresponds to the distance between the lines v d, Fig. 171. This measurement can be got by removing both end stones and taking the distance with a Boley gage or a douzieme caliper.

A CONVENIENT TOOL FOR LENGTH MEASUREMENT.



A pair of common pinion calipers slightly modified makes as good a pair of calipers for length measurement as one can desire. This instrument is made by inserting a small screw in one of the blades—the head on the inner side, as shown at f, Fig. 180. The idea of the tool is, the screw head f rests in the sink of the cap jewel or end stone, while the other blade rests on the cock over the balance. After the adjusting screw to the caliper is set, the spring of the blades allows of their removal. The top pivot z of the cylinder is next cut to the proper length, as indicated by the space between the screwhead f and the other blade of the pinion caliper. The upper pinion z is held in the jaws of the cutting pliers, as shown in Fig. 177, the same as the lower one was held, until the proper length between the lines d v, Fig. 171, is secured, after which the cylinder is put back into the cement chuck, as shown at Fig. 178, except this time the top portion of the cylinder is allowed to protrude so that we can turn the top pivot and the balance collet D, Fig. 171.

The sizes we have now to look to is to fit the pivot z to the top hole jewel in the cock, also the hairspring seat D and balance seat D'. These are turned to diameters, and are the most readily secured by the use of the micrometer calipers to be had of any large watchmakers' tool and supply house. In addition to the diameters named, we must get the proper height for the balance, which is represented by the dotted line b. The measurement for this can usually be obtained from the old cylinder by simply comparing it with the new one as it rests in the cement chuck. The true tool for such measurements is a height gage. We have made no mention of finishing and polishing the pivots, as these points are generally well understood by the trade.

REMOVING THE LATHE CEMENT.

One point perhaps we might well say a few words on, and this is in regard to removing the lathe cement. Such cement is usually removed by boiling in a copper dish with alcohol. But there are several objections to the practice. In the first place, it wastes a good deal of alcohol, and also leaves the work stained. We can accomplish this operation quicker, and save alcohol, by putting the cylinder with the wax on it in a very small homeopathic bottle and corking it tight. The bottle is then boiled in water, and in a few seconds the shellac is dissolved away. The balance to most cylinder watches is of red brass, and in some instances of low karat gold; in either case the balance should be repolished. To do this dip in a strong solution of cyanide of potassium dissolved in water; one-fourth ounce of cyanide in half pint of water is about the proper strength. Dip and rinse, then polish with a chamois buff and rouge.



In staking on the balance, care should be observed to set the banking pin in the rim so it will come right; this is usually secured by setting said pin so it stands opposite to the opening in the half shell. The seat of the balance on the collet D should be undercut so that there is only an edge to rivet down on the balance. This will be better understood by inspecting Fig. 181, where we show a vertical section of the collet D and cylinder A. At g g is shown the undercut edge of the balance seat, which is folded over as the balance is rivetted fast.

About all that remains now to be done is to true up the balance and bring it to poise. The practice frequently adopted to poise a plain balance is to file it with a half-round file on the inside, in order not to show any detraction when looking at the outer edge of the rim. A better and quicker plan is to place the balance in a split chuck, and with a diamond or round-pointed tool scoop out a little piece of metal as the balance revolves. In doing this, the spindle of the lathe is turned by the hand grasping the pulley between the finger and thumb. The so-called diamond and round-pointed tools are shown at o o', Fig. 182. The idea of this plan of reducing the weight of a balance is, one of the tools o is rested on the T-rest and pressed forward until a chip is started and allowed to enter until sufficient metal is engaged, then, by swinging down on the handle of the tool, the chip is taken out.



In placing a balance in a step chuck, the banking pin is caused to enter one of the three slots in the chuck, so as not to be bent down on to the rim of the balance. It is seldom the depth between the cylinder and escape wheel will need be changed after putting in a new cylinder; if such is the case, however, move the chariot—we mean the cock attached to the lower plate. Do not attempt to change the depth by manipulating the balance cock. Fig. 183 shows, at h h, the form of chip taken out by the tool o o', Fig. 182.



INDEX

A

Acid frosting, 46

"Action" drawings, 90

Action of a chronometer escapement, 142

Acting surface of entrance lip, 127

Actions of cylinder escapement, 112

Adhesion of parallel surfaces, 94

Adjustable pallets, 98

Adjusting screw for drawing instruments, 21

Analysis of principles involved in detent, 137

Analysis of the action of a lever escapement, 86

Angle-measuring device, 68

Angular extent of shell of cylinder, 122

Angular motion, drawing an escapement to show, 91 How measured, 69 Of escape wheel, 37

Antagonistic influences, 133

Arc of degrees, 9

Atmospheric disturbances, 74

Attainment of isochronism, 159

B

Balance, how it controls timekeeping, 73 Weight and inertia of, 133

Balance spring, inventor of, 132

Banking slot of cylinder, 112

Bankings, effect of opening too wide, 63

Bar compasses, 21

Barometric pressure, 74

Basis for close measurements, 96

C

Cement chuck, how to use, 173

Chronometer detent, importance of light construction, 136

Chronometer escapement, 131, 155 Four principal parts of, 134

Circular pallets, 27

Club-tooth escapement, 30, 34

Club-tooth lever escapement with circular pallets and tangential lockings, 83

Crown-wheel escapement, 155

Cylinder, drawing a, 120 Outer diameter of, 116 Putting in a new, 169

Cylinder escapement, 155 Date of invention, etc., 111 Forms and proportions of several parts of, 111 Names of various parts, 112

Cylinder lips, proper shape of, 124

D

Dead-beat escapement, 131, 135 Only one true, 112

Depth, between cylinder and escape wheel, 129 Effect of changing, 176

Designing a double roller, 77

Detached escapement, 155

Detent, functions of the, 137

Detent escapement, 131, 155 Faults in, 132

Detent spring dimensions, 138

Detent springs, width of, 147

Discharging jewel, setting the, 142

Discharging roller, 136

Dividers, 9 Making, 10

Double pendulum, 160

Double-roller escapement, 75

Draw defined, 85

Drawing-board, 11

Drawing instruments, 9

Drawings, advantage of large, 29

Drop and draw, 150

Duplex escapement, 131, 155

E

Elasticity of spring, 133

Engaging friction, 81

English recoil anchor, 167

Entrance lip of cylinder escapement, 125

Escapement angles, measuring, 101

Escapement error, study of, 64

Escapement matching tool, 106

Escapement model, 40 Balance, 42 Balance staff, 44 Bridges, 41, 42 Escape wheel, 43 Extra balance cock, 45 "Frosting", 46 Hairspring, 42 Jewel for, 43 Lower plate, 41 Main plate, 41 Movement for, 41 Pallet staff, 42 Pillars, 43 Regulator, 46 Uses of, 44 Wood base for, 41

Escapements compared, 103

Escapement of Dutertre, 160

Escape-wheel action, 30

Escape-wheel, delineating an, 11

Escape-wheel teeth vs. cylinder, 169

Escape-wheel tooth in action, delineating an, 126

Exit pallet, 26

Experiments of Galileo, 158

Experiments with a chronometer, 142

Extent of angular impulse, 118

F

"Fall" defined, 106

Faults in the detent escapement, 132

Fixed rules, of little value to student, 137

Flexure of gold spring, 146

Foot, fitting up the, 151

Fork, testing the, 71

Fork action, 30 Theory of, 59

Fork and roller action, 54

Formulas for delineating cylinder escapement, 115

Frictions, 24

Frictional escapement, 131, 132

Frictional surfaces, 63

Fusee, 131

G

Gable escapement, 167

Gage, a new, 172

Graham anchor escapement, 155

Gold spring, 146

Guard point, 79 Material for, 79

Gummy secretion on impulse and discharging stones, 147

H

Heights in cylinders, how obtained, 171

Hole jewels, distance apart, 140

I

Imaginary faults in cylinders, 129

Impulse angle, 118

Impulse arc, extent of, 134

Impulse jewel set oblique, 147

Impulse planes, locating outer angle of, 39

Impulse roller, 136

Incline of teeth, 122

Inertia of balance, 133

Inventions of Berthoud, 163 Bethune, 165 Clement, 166 Dr. Hook, 162 Harrison, 161 Hautefeuille, 161 Huygens, 158 Leroy, 163 Thiout, 165

J

Jewel pin, determining size, 58 Cementing in, 67 Settings, 66

Jewel-pin setters, 67

L

Lathe cement, 173 Removing, 175

Lever, proper length of, 61

Lever fork, horn of, 61 prongs of, 60

Lift, real and apparent, 112

Lifting angle, 114

Lock, amount of, 28 Defined, 85

Lock and drop testing, 69

Locking jewel, moving the, 149

Locking stone, good form of, 144

Lower plate, circular opening in, 56

M

Marine chronometer, number of beats to hour, 148

Mathematics, 95

Measuring tools, 171

Metal drawings, advantages of, 140

Motion, how obtained, 16

Movement holder, 110

N

Neutral lockings, 84

O

Original designing, 148

P

Pallet action, locating the, 90

Pallet-and-fork action, 12, 13, 17, 18

Pallet stones, how to set, 104

Pallets, adjusting to match the fork, 65

Paper for drawing, 11

Parts, relations of the, 32

Passing hollow, 62

Perfected lever escapement, 87

Pivots, turning, 172

Point of percussion, 139

Points for drawing instruments, 20

Polishing materials, 52

Power leaks, 16

Power lost in lever escapement, 87

Practical problems in the lever escapement, 98

R

Radial extent of outside of cylinder, 125

Ratchet-tooth escape wheel, 12

Recoil anchor escapement, 155

Recoil escapement, 154

Reduced gable escapement, 167

Retrograde motion, 36

Roller action, why 30 degrees, 55 Of double roller, 78

Roller diameter, determining the, 55

Ruling pen, 9

S

Safety action, 56

Scale of inches, 9

Screws, making extra large, 45

Screwheads, fancy, 45

Selecting new cylinder, 170

Shaping, advantages gained in, 116

Sheet steel, cutting, 48

Short fork, 100

Sound as indicator of correct action, 144

Spring, elasticity of, 133

Staking on a balance, 175

Steel, polishing, 49 Tempering, 49

Study drawings, 124

Systems of measurements, 114

T

Tangential lockings, 80, 148

Test gage for angular movement, 65

Theoretical action of double roller, 76

Timekeeping, controlled by balance, 73

Tool for length measurement, 174

Tools, measuring, 171

Triangle, 18

T-square, 9

U

Unlocking action, 56

Unlocking roller, 136

V

Verge escapement, 131, 155

W

Weight and inertia of balance, 133

Working model of cylinder escapement, 123



* * * * * *



THE WATCH ADJUSTER'S MANUAL



A Complete and Practical Guide for Watchmakers in Adjusting Watches and Chronometers for Isochronism, Position, Heat and Cold.

BY CHARLES EDGAR FRITTS (EXCELSIOR),

Author of "Practical Hints on Watch Repairing," "Practical Treatise on Balance Spring," "Electricity and Magnetism for Watchmakers," etc., etc.

This well-known work is now recognized as the standard authority on the adjustments and kindred subjects, both here and in England. It contains an exhaustive consideration of the various theories proposed, the mechanical principles on which the adjustments are based, and the different methods followed in actual practice, giving all that is publicly known in the trade, with a large amount of entirely new practical matter not to be found elsewhere, obtained from the best manufacturers and workmen, as well as from the author's own studies and experiences.

Sent postpaid to any part of the world on receipt of $2.50 (10s. 5d.)

THE KEYSTONE (SOLE AGENT), 19TH AND BROWN STREETS, PHILADELPHIA, U.S.A.

* * * * *

THE ART OF ENGRAVING



A Complete Treatise on the Engraver's Art, with Special Reference to Letter and Monogram Engraving. Specially Compiled as a Standard Text-Book for Students and a Reliable Reference Book for Engravers.

This work is the only thoroughly reliable and exhaustive treatise published on this important subject. It is an ideal text-book, beginning with the rudiments and leading the student step by step to a complete and practical mastery of the art. Back of the authorship is a long experience as a successful engraver, also a successful career as an instructor in engraving. These qualifications ensure accuracy and reliability of matter, and such a course of instruction as is best for the learner and qualified engraver.

The most notable feature of the new treatise is the instructive character of the illustrations. There are over 200 original illustrations by the author. A very complete index facilitates reference to any required topic.

Bound in Silk Cloth—208 Pages and 216 Illustrations.

Sent postpaid to any part of the world on receipt of price, $1.50 (6s. 3d.)

PUBLISHED BY THE KEYSTONE, THE ORGAN OF THE JEWELRY AND OPTICAL TRADES, 19TH & BROWN STS., PHILADELPHIA, U.S.A.

* * * * *

THE KEYSTONE PORTFOLIO OF MONOGRAMS



This portfolio contains 121 combination designs. These designs were selected from the best of those submitted in a prize competition held by The Keystone, and will be found of value to every one doing engraving.

The designs are conceded to be the best in the market, excelling in art and novelty of combination and skill in execution.

They are printed from steel plates on stiff, durable paper, and contain sample monograms in a variety of combinations.

The portfolio is a bench requirement that no jeweler can afford to be without. It is a necessary supplement to any text-book on letter engraving.

Price, 50 Cents (2s.)

PUBLISHED BY THE KEYSTONE, THE ORGAN OF THE JEWELRY AND OPTICAL TRADES, 19TH & BROWN STS., PHILADELPHIA, U.S.A.

* * * * *

THE OPTICIAN'S MANUAL

VOL. I.

BY C.H. BROWN, M.D.

Graduate University of Pennsylvania; Professor of Optics and Refraction; formerly Physician in Philadelphia Hospital; Member of Philadelphia County, Pennsylvania State and American Medical Societies.



The Optician's Manual, Vol. I., has proved to be the most popular work on practical refraction ever published. The knowledge it contains has been more effective in building up the optical profession than any other educational factor. A study of it is essential to an intelligent appreciation of Vol. II., for it lays the foundation structure of all optical knowledge, as the titles of its ten chapters show:

Chapter I.—Introductory Remarks. Chapter II.—The Eye Anatomically. Chapter III.—The Eye Optically; or, The Physiology of Vision. Chapter IV.—Optics. Chapter V.—Lenses. Chapter VI.—Numbering of Lenses. Chapter VII.—The Use and Value of Glasses. Chapter VIII.—Outfit Required. Chapter IX.—Method of Examination. Chapter X.—Presbyopia.

The Optician's Manual, Vol. I., is complete in itself, and has been the entire optical education of many successful opticians. For student and teacher it is the best treatise of its kind, being simple in style, accurate in statement and comprehensive in its treatment of refractive procedure and problems. It merits the place of honor beside Vol. II. in every optical library.

Bound in Cloth—422 pages—colored plates and Illustrations.

Sent postpaid on receipt of $2.00 (8s. 4d.)

PUBLISHED BY THE KEYSTONE, THE ORGAN OF THE JEWELRY AND OPTICAL TRADES, 19TH & BROWN STS., PHILADELPHIA, U.S.A.

* * * * *

THE OPTICIAN'S MANUAL

VOL. II.

BY C.H. BROWN, M.D.

Graduate University of Pennsylvania; Professor of Optics and Refraction; formerly Physician in Philadelphia Hospital; Member of Philadelphia County, Pennsylvania State and American Medical Societies.



The Optician's Manual, Vol. II., is a direct continuation of The Optician's Manual, Vol. I., being a much more advanced and comprehensive treatise. It covers in minutest detail the four great subdivisions of practical eye refraction, viz:

Myopia. Hypermetropia. Astigmatism. Muscular Anomalies.

It contains the most authoritative and complete researches up to date on these subjects, treated by the master hand of an eminent oculist and optical teacher. It is thoroughly practical, explicit in statement and accurate as to fact. All refractive errors and complications are clearly explained, and the methods of correction thoroughly elucidated.

This book fills the last great want in higher refractive optics, and the knowledge contained in it marks the standard of professionalism.

Bound in Cloth—408 pages—with illustrations.

Sent postpaid on receipt of $2.00 (8s. 4d.)

PUBLISHED BY THE KEYSTONE, THE ORGAN OF THE JEWELRY AND OPTICAL TRADES, 19TH & BROWN STS., PHILADELPHIA, U.S.A.

* * * * *

SKIASCOPY AND THE USE OF THE RETINOSCOPE



A Treatise on the Shadow Test in its Practical Application to the Work of Refraction, with an Explanation in Detail of the Optical Principles on which the Science is Based.

This new work, the sale of which has already necessitated a second edition, far excels all previous treatises on the subject in comprehensiveness and practical value to the refractionist. It not only explains the test, but expounds fully and explicitly the principles underlying it—not only the phenomena revealed by the test, but the why and wherefore of such phenomena.

It contains a full description of skiascopic apparatus, including the latest and most approved instruments.

In depth of research, wealth of illustration and scientific completeness this work is unique.

Bound in cloth; contains 231 pages and 73 illustrations and colored plates.

Sent postpaid to any part of the world on receipt of $1.00 (4s. 2d.)

PUBLISHED BY THE KEYSTONE, THE ORGAN OF THE JEWELRY AND OPTICAL TRADES, 19TH AND BROWN STS., PHILADELPHIA, U.S.A.

* * * * *

PHYSIOLOGIC OPTICS

Ocular Dioptrics—Functions of the Retina—Ocular Movements and Binocular Vision

BY DR. M. TSCHERNING

Adjunct-Director of the Laboratory of Ophthalmology at the Sorbonne, Paris

AUTHORIZED TRANSLATION

BY CARL WEILAND, M.D.

Former Chief of Clinic in the Eye Department of the Jefferson College Hospital, Philadelphia, Pa.

This is the crowning work on physiologic optics, and will mark a new era in optical study. Its distinguished author is recognized in the world of science as the greatest living authority on this subject, and his book embodies not only his own researches, but those of the several hundred investigators who, in the past hundred years, made the eye their specialty and life study.

Tscherning has sifted the gold of all optical research from the dross, and his book, as now published in English with many additions, is the most valuable mine of reliable optical knowledge within reach of ophthalmologists. It contains 380 pages and 212 illustrations, and its reference list comprises the entire galaxy of scientists who have made the century famous in the world of optics.

The chapters on Ophthalmometry, Ophthalmoscopy, Accommodation, Astigmatism, Aberration and Entoptic Phenomena, etc.—in fact, the entire book contains so much that is new, practical and necessary that no refractionist can afford to be without it.

Bound in Cloth. 380 Pages, 212 Illustrations.

Price, $3.50 (14s. 7d.)

PUBLISHED BY THE KEYSTONE, THE ORGAN OF THE JEWELRY AND OPTICAL TRADES, 19TH & BROWN STS., PHILADELPHIA, U.S.A.

* * * * *

OPHTHALMIC LENSES

Dioptric Formulae for Combined Cylindrical Lenses, The Prism-Dioptry and Other Original Papers

BY CHARLES F. PRENTICE, M.E.

A new and revised edition of all the original papers of this noted author, combined in one volume. In this revised form, with the addition of recent research, these standard papers are of increased value. Combined for the first time in one volume, they are the greatest compilation on the subject of lenses extant.

This book of over 200 pages contains the following papers:

Ophthalmic Lenses. Dioptric Formulae for Combined Cylindrical Lenses. The Prism-Dioptry. A Metric System of Numbering and Measuring Prisms. The Relation of the Prism-Dioptry to the Meter Angle. The Relation of the Prism-Dioptry to the Lens-Dioptry. The Perfected Prismometer. The Prismometric Scale. On the Practical Execution of Ophthalmic Prescriptions involving Prisms. A Problem in Cemented Bi-Focal Lenses, Solved by the Prism-Dioptry. Why Strong Contra-Generic Lenses of Equal Power Fail to Neutralize Each Other. The Advantages of the Sphero-Toric Lens. The Iris, as Diaphragm and Photostat. The Typoscope. The Correction of Depleted Dynamic Refraction (Presbyopia).

Press Notices on the Original Edition:

OPHTHALMIC LENSES.

"The work stands alone, in its present form, a compendium of the various laws of physics relative to this subject that are so difficult of access in scattered treatises."—New England Medical Gazette.

"It is the most complete and best illustrated book on this special subject ever published."—Horological Review, New York.

"Of all the simple treatises on the properties of lenses that we have seen, this is incomparably the best.... The teacher of the average medical student will hail this little work as a great boon."—Archives of Ophthalmology, edited by H. Knapp, M.D.

DIOPTRIC FORMULAE FOR COMBINED CYLINDRICAL LENSES.

"This little brochure solves the problem of combined cylinders in all its aspects, and in a manner simple enough for the comprehension of the average student of ophthalmology. The author is to be congratulated upon the success that has crowned his labors, for nowhere is there to be found so simple and yet so complete an explanation as is contained in these pages."—Archives of Ophthalmology, edited by H. Knapp, M.D.

"This exhaustive work of Mr. Prentice is a solution of one of the most difficult problems in ophthalmological optics. Thanks are due to Mr. Prentice for the excellent manner in which he has elucidated a subject which has not hitherto been satisfactorily explained."—The Ophthalmic Review, London.

The book contains 110 Original Diagrams. Bound in cloth.

Price, $1.50 (6s. 3d.)

PUBLISHED BY THE KEYSTONE, THE ORGAN OF THE JEWELRY AND OPTICAL TRADES, 19TH & BROWN STS., PHILADELPHIA, U.S.A.

* * * * *

OPTOMETRIC RECORD BOOK

A record book, wherein to record optometric examinations, is an indispensable adjunct of an optician's outfit.

The Keystone Optometric Record Book was specially prepared for this purpose. It excels all others in being not only a record book, but an invaluable guide in examination.

The book contains two hundred record forms with printed headings, suggesting, in the proper order, the course of examination that should be pursued to obtain most accurate results.

Each book has an index, which enables the optician to refer instantly to the case of any particular patient.

The Keystone Record Book diminishes the time and labor required for examinations, obviates possible oversights from carelessness and assures a systematic and thorough examination of the eye, as well as furnishes a permanent record of all examinations.

Sent postpaid on receipt of $1.00 (4s. 2d.)

PUBLISHED BY THE KEYSTONE, THE ORGAN OF THE JEWELRY AND OPTICAL TRADES, 19TH & BROWN STS., PHILADELPHIA, U.S.A.

* * * * *

THE KEYSTONE BOOK OF MONOGRAMS

This book contains 2400 designs and over 6000 different combinations of two and three letters.

Is an essential to every jeweler's outfit. It is not only necessary for the jeweler's own use and guidance, but also to enable customers to indicate exactly what they want, thus saving time and possible dissatisfaction.

The Monograms are purposely left in outline, in order to show clearly how the letters are intertwined or woven together. This permits such enlargement or reduction of the Monogram as may be desired, and as much shading, ornamentation and artistic finish as the jeweler may wish to add.

This comprehensive compilation of Monograms is especially available as a reference book in busy seasons. Its use saves time, thought and labor, and ensures quick and satisfactory work.

Monograms are the fad of the time, and there's money for the jeweler in Monogram engraving. The knowledge in this book can be turned into cash. All the various styles of letters are illustrated.

Price, $1.00 (4s. 2d.)

PUBLISHED BY THE KEYSTONE, THE ORGAN OF THE JEWELRY AND OPTICAL TRADES, 19TH & BROWN STS., PHILADELPHIA, U.S.A.

* * * * *

THE KEYSTONE RECORD BOOK OF WATCH REPAIRS

This book is 9 x 11 inches, has 120 pages, and space for recording sixteen hundred jobs in detail. It is made of linen ledger paper, bound in cloth with leather back and corners.

Price, $1.00 (4s. 2d.), prepaid.

No other record book on the market is so complete, and all cost more.

PUBLISHED BY THE KEYSTONE, THE ORGAN OF THE JEWELRY AND OPTICAL TRADES, 19TH & BROWN STS., PHILADELPHIA, U.S.A.

* * * * *

THE KEYSTONE BOOK OF GUARANTEES OF WATCH REPAIRS

This book contains two hundred printed guarantees, and is handsomely bound. Each guarantee is 31/4 x 71/2 inches, and most carefully worded. Jewelers have discovered that the use of these guarantees is a most effective way to secure and cultivate public confidence. We sell a book of two hundred for

$1.00 (4s. 2d.), prepaid,

which is one-third less than the price charged by others for a similar book.

PUBLISHED BY THE KEYSTONE, THE ORGAN OF THE JEWELRY AND OPTICAL TRADES, 19TH & BROWN STS., PHILADELPHIA, U.S.A.

THE END