The great hammer carries a pin 3, Fig. 4. which comes up to the motion work through an opening marked 3, Fig. 3.: the spring r acts on this pin, and causes the great hammer to strike : this hammer carries another pin 2, which passes also through to the motion work by an opening '2, Fig. 3. ; it is upon this that the small tail of the raising pieces acts, to make it give blows for the quarters : the small hammer has also a pin which passes through to the motion work by the opening 4 ; it is upon this pin that the spring 7 presses, to cause the quarter hammer to strike. The spring S is the spring jumper, which acts on the star wheel, E.
Figure 6. represents the cannon pinion and the quarter snail N, seen in perspective. The quarter snail N is rivetted on the cannon pinion c, the end of which D car ries the minute hand ; this snail N carries the surprise S, the effect of which is the same as that for the repeating clock ; that is to say, when the pin 0 of the surprise shifts the place, or causes the star to advance, and the jumper having done turning it, one of the teeth of the star comes to touch the pin 0 which is carried by the sur prise, and causes the part of the surprise Z, Fig. 3. to advance, so that when the arm Q of the quarter rack falls on this part Z, and prevents it from falling on the step 3 of the snail ; by this the piece repeats only the hour. The changing from one hour to another is by this way made in an instant, and the watch strikes the hour exactly as marked by the hands. The socket or cannon of the cannon pinion c ll, Fig. 6. is slit, in order that it may move spring tight on the arbor of the second wheel, on which it enters with a degree of stiffness or friction, slight enough to be able to turn easily the minute hand to either side, by setting it back sir forward according as it may be required, which sets also the hour hand to the hours.
It is proper here to undeceive those who think that they injure their watches in setting the minute hand backward. in order to convince one's self that there is nothing in this, it is sufficient to remark the position which the pieces must have in a repeating motion work, when it has to repeat the hour, when the pendant or pusher has brought back and set aside all the pieces which communicate with the snails L, N ; for at this time there is no communication or connection between the pieces of the movement and those of the motion work, but that of the pin 0 of the snail or surprise, with the teeth of the star wheel E, which nothing can prevent from retrograd ing. If then the minute hand is made to make a com
plete turn backward, the pin 0 will also make one of the teeth of the star to retrograde ; and if the watch is made afterwards to repeat, it will strike always the hours and quarters as marked by the hands. But it must be ob served, that if the hands were turned in the same instant that the watch is made to repeat, they would then be pre vented : it is necessary then, before touching the hands of a repeating clock or watch, to wait till'it has repeated the thour, so that all the pieces shall have taken their natural situations.
It is easy to conclude from this, that since with a repeat big watch, we can set backward or forward the minute hand, according as it may be required, we may with much greater reason do this in a plain watch, where no obstacle is opposed to it.
As to the hour hand of a repeating watch, it ought never to be turned without that being done by the minute hand alone ; except in that case where the repeater does not strike the hour marked by the hour hand, when it would be necessary to put it to the hour which the repeater strikes.
\Vhen the repeater gets of itself deranged, by the hour hand not according with the hour which the watch strikes, this is a proof that the jumper S. or the pin 0 of the snail, do not produce well the ( ffect they ought to have.
The returning or minute wheel, Fig. 6. is placed, and turns on the stud 12, Fig. 1.: this wheel pitches into the can non piMon N, which has twelve teeth ; the wheel, Fig. 6. has thirty-six ; the cannon pinion then makes three turns whilst it makes one ; this carries a pinion of ten teeth, which pitches or leads the hour wheel, Fig. 7. which has forty ; the wheel, Fig 8. makes then four turns for one of the hour wheel ; the cannon pillion consequently makes twelve turns for one of the hour wheel, and the cannon pinion makes one turn in an hour ; the hour wheel takes then twelve hours to make one revolution ; it is the socket of the hour wheel which carries the hour hand. The raising or lifting piece m, n, Fig. 2. can only describe a small arc, which permits the ratchet R to retrograde ; and so soon as the mover brings it back, the arm I of the raising piece draws the hammer M.