The first watches may readily be supposed to have been of rude execution. Having no pendulum spring, and only an hour hand, and being wound up twice a day, they could not be expected to keep time nearer than 15 or 20 minutes in the twelve hours. After the application of the pendu lum spring, they would no doubt go considerably better, and may now be made to keep time sufficiently correct for the ordinary' purposes of life. Indeed, when the crown wheel and verge 'scapement is executed with care, it wilt do uncommonly well. Let the angle of the verge be 93 or 95 degrees, the teeth or the crown wheel undercut to an angle of 28 or 30 degrees, and scaped as near to the body of the verge as just to be clear of it, (it is to be understood here that the verge holes are jewelled.) To carry the mat ter still farther, the body may so far be taken away as to ad mit the teeth near to the centre, which will tend to allow the vibrations of the balance to move more freely and indepen dently ; but this requires such nice execution here, and in other parts of the 'scapement, that from not having encou ragement, few arc fit to execute it, and therefore it may in general be safer not to bring the wheel teeth so near to the verge. Care must also be taken to have the balance of a proper diameter and weight, which has of late been much neglected since the old fashion of half timing has been left off, that is, making the watch go without the pendulum spring, if it goes slow 30, 32, or 33 minutes in the hour, the balance may be considered of such a weight as to be in no danger of knocking on the banking from any exter nal motion the watch may meet with in fair wearing. When the pallets of the verge are banked on pins in the potence, they should, to prevent straining, both bank at the same time, alternately the face of one pallet on a pin, when the back of the other is on its pin ; or the banking may be done by a pin in the rim of the balance, but not near the edge of it. Which of the two is preferable, we shall not stop to determine.
The verge watch, as has been already said, when proper ly executed, will perform extremely well. About thirty years ago or more, the writer of this article had some of them made up in such a way, that they went fully as well as any horizontal 'scapement, and for a longer time ; this last requiring oil to the cylinder, after going ten or twelve months. Oil, however, should never he allowed to come near the wheel teeth or pallets of a verge. Verge or con trate wheel watches have, of late years. been very much overlooked and neglected in many respects, and in none more so than in the relative position of the balance wheel, and contrate wheel arbors. They are rarely seen but at a considerable distance from one another, which gives a very oblique direction in the pitching of the contrate wheel with the balance wheel pinion. It is well known, that where force is indirectly or obliquely applied, it will work under great disadvantage. These arbors ought to be placed as near to each other as can be. In order to obtain this, re duce the balance wheel pinion arbor towards the end to the smallest size it will bear, and turning a hollow out of that of the cont'rate wheel, will allow them to come very near the line of their centres. To get this pitching to the greatest
advantage, some place the counter potence within the arbor of the contrate wheel, so as to have the line of the balance wheel pinion direct to the centre of the contrate wheel, as may be seen in Plate CCC I I. Fig. I.
It has been recommended by a very celebrated artist, that the movement wheels should be placed in such a man ner as to act at equal distances from the pivots of those pi nions which they drive, in order to divide the pressure or action of the wheel between the pivots, and that one should not bear more than the other. This is apparently sound reasoning ; but having put it in execution, the pivots unex pectedly seemed to wear very fast, even more so than in the common barred movement ; the pivots, it is true, were small, and the motive force rather great. It is to be wish ed that it were again tried by others to bring it to the test. No pivots have been found to stand so well as those in movements of the double barred sort.
A pendulum spring collet, made as it ought to be, is as seldom to be met with, as that which we have noticed re garding the position of the contrate and balance wheel ar bors. Yet simple as the thing is, it seems to require a rule to spew how it should be done, there appearing to be none, if we may judge by the greatest part of those which have hitherto been made. The ring of the collet should be no broader than to allow a hole to receive the pendulum spring, and the pin which fixes it. The slit in the collet, for the purpose of its being always spring tight on the inside taper of a cylinder or verge collet, should be put close to where the small end of the pin comes, when the spring is pinned in. The pendulum spring, in this case, will have the first or in ner coil at such a distance, as to allow the point of a small screwdriver to get into the slit without any danger to the spring, when it is wanted to set the collet and spring to any required place. If the slit is put at the other end of the pin, where it is oftener than anywhere else, it is evident that the workman cannot get into it without danger. The outer end of the pendulum spring ought to be pinned or fixed into a brass stud or cock, in performing which opera tion it goes easily on ; whereas with steel cocks or studs, there is a kind of crossness and trouble, which shews that they should never be used.
Studs are, in general, very improperly placed, being at a greater distance from the curb pins than is requisite. We have seen this distance so great„that the' motion of the pendulum spring between the stud and the'pins was such, as to take away a part from every vibration of the balance; which is something like a pendulum when suspended to a vibratory cock, where it would not be allowed to have half the motion it would otherwise have acquired.