WATCH. 



Fig, 4. reprefents the pinion C, and the hour and quarter 

 ratchets N and O, feparate in plan, and in profile ; and alfo 

 a feftion of tlie tliree together. 



Fig. 5. reprefents the cannon-pinion tu feen from above, 

 as well as below ; and alfo in perfpeftive, with the quarter- 

 fiiail G attached to it. 



Fig. 6. reprefents the wheel Q of 48, the hour-fnail F, 

 the retrograding ratchet P, and the wheel of communication 

 R, feparate in plan, and in profile; and alfo a feilion of 

 them together. 



Fig. "J. reprefents the hour-fnail F on thewheelQof 48, and 

 the little fpring s in the notch of the focket of the hour-fnail. 



The rack AB (fee Plale XLVl. Jigs, i, 2, and 3.) is 

 the piece firft put in motion when the watch is made to re- 

 peat, and is that by the aftion of which with the pinion C 

 of twenty teeth, concealed mjigs. I. and 2. by the hour and 

 quarter ratchets N and O, the main-fpring of the repeating 

 part is wound up ; this rack may be confidered as a portion of 

 ayery large wheel, whofe axis or centre of motion is placed, as 

 near as it conveniently can be, to the edge of the watch : this 

 axi» is a hollow tube, palling through a well fitted hole in the 

 pillar-plate, and pivoted into the upper plate ; ( the reafon of 

 its being a tube will be prefently fhewn ;) it is fet upright in 

 the frame, and confequently at right angles to the face of the 

 pillar-plate ; hence it follows, that the rack, which is alfo 

 fixed at right angles to its axis, moves parallel to the pillar- 

 plate, and is placed as near the plate as it can be, to move 

 freely without rubbing it ; the rack is cut into twenty-two 

 teeth. Immediately connefted with the rack are the two 

 pieces D and E, called, the piece D the unlocking-arm, and 

 the piece E the quarter-rack : the ufe of the piece D is two- 

 fold ; firft, to determine tlie number of blows to be ftruck 

 by the great or hour-hammer, by means of its army, which, 

 when the watch is made to repeat, comes to bear upon one 

 of the fteps of the hour-fnail F ; fecond, to unlock, or, as it 

 is commonly termed, difcharge the ilriking. This efTift is 

 produced, as will be explained hereafter, by a motion of the 

 piece D peculiar to itfelf. This piece D is attached to the 

 rack, at its greateft dillance from its centre of motion, by 

 the fcrew i, which fcrcw is tapped into the rack up to a 

 fhoulder, leaving a plain part equal to the thicknefs of the 

 piece D, and as much more as is neccffary for the piece not 

 to be bound, between the under fide of the fcrew head and 

 the upper furface of the rack ; and the hole in the piece D, 

 through which this fcrew i paffts, is made to fit very cor- 

 redlly on the plain part of the fcrew, upon which it moves 

 as its centre of motion. The quantity of motion of the 

 piece D is determined by a circular hole at its other ex- 

 tremity, through which the axis of the rack paffcs, fome- 

 v;hat larger than that axis, which, in order to pafs through 

 the end of this piece D, and for it to aft againil, is purpofely 

 prolonged above the furface of the rack, a very little more 

 than the thicknefs of this fame piece D : in fig. 3. the qnar- 

 ter-rack and the cock a are omitted to ihew the fhape of this 

 piece. 



The quarter-rack E, fituated above the piece D, has its 

 centre of motion within the centre of motion of the rack 

 A B, or conlidcring the centres of mouon of both the 

 pieces as lines, they may, under that fuppofition, be con- 

 fidered as polTcfling one common centre of motion : this rack 

 is alfo fixed at rigl;t angles to its axis, which pafTes through 

 the tube that forms the axis of the rack A B, the whole 

 length of that axis to the upper plate ; the under fide of this 

 quarter-rack bears upon the top of the tube, or centre of 

 motion of the great rack, which terminaCes a little above 

 the centre of motion of the piece D, as has been before 

 mentioned ; and the upper extremity e of the axis of this 



piece is pivoted into the cock a, figs, i and 2, uJiich cock is 

 fcrewed faft to the pillar-plate Y Z : in this manner is the 

 quarter-rack confined in its place between the upper end of 

 the hollow arbor of the rack A B, prolonged through the 

 piece D, as before defcribed, and the under fide of the 

 cock a. The ufe of this piece is to determine the number 

 of quarters, if any, or the half-quarter, as the cafe may be, 

 to be repeated after the hour : this effeft is produced by the 

 aftion of one, and one only, of the eight teeth at the end of 

 the rack, on the little all-or-nothing piece I ; and according 

 to the tooth which fo afts, the v.atch, after having repeated 

 the hour, repeats the half-quarter, the quarter, or the quar- 

 ter and half-quarter, &c. as fliewn by the hands ; or if the 

 minute-hand has not paffed the 7'^ and 30' after the hour, the 

 firft tooth of the eight caufes the repeating to ceafe imme- 

 diately after the repeating of the hour is completed. Which 

 of the teeth (hall aft on the little all-or-nothing piece is de- 

 termined by the advance of the quarter-rack, which is regu- 

 lated by the ftep on the quarter-fnail G, upon which the 

 zrm y comes in contaft, when the watch io made to repeat. 

 The arm y is made a feparate piece from and fixed to the 

 quarter-rack E, by means of the fcrew 2, on which fcrew it 

 moves as its centre of motion, in the fame manner as the 

 piece D moves on the fcrew i , and is kept in its place by 

 the fpring g : the reafon of this piece being thus made, is to 

 prevent the poftibility, in the cafe of the watch being made 

 to repeat exaftly at the quarter, of the repeating work ftop- 

 ping the watch, by the arm ji holding back the quarter-fnail, 

 during the ftriking of the hours : the arm 0, which is a por- 

 tion of the quarter-rack, by its aftion with the retrograding- 

 ratchet P, brings the hour-fnail F into its proper place to 

 receive the arm /, of the piece D. The quarter-rack E 

 is kept in its place by the pin 3, tapped into the piece D, 

 which bears againft its edge ; and is carried forward when 

 the watch is made to repeat, by the aftion of its fpring h, 

 which is fcrewed to its extremity the fartheft from the 

 centre of its motion, and let up by its other extremity 

 being confined in a notch in the cock a. 



The total furface of the piece D refts on the rack A B, 

 and, confequently when, in the aft of unlocking, it moves 

 on its centre, or fcrew i, its under face rubs on the furface 

 of the rack A B ; but the quarter-rack E, on the con- 

 trary, is entirely detached from, and does not touch the 

 furface of the piece D, its under fide bearing upon the 

 prolonged arbor of the rack A B, through the hole in 

 the piece D ; and is kept down by the cock a, which 

 bears againft the ihoulder of its upper pivot, as has 

 been before mentioned. There is what is termed, in the 

 peculiar dialcft of watch-makers, a light between the under 

 lide of the rack and the pillar-plate, and between the under 

 fide of the quarter-rack and the piece D ; and from their 

 conftruftion, it is evident that they move in planes parallel 

 to one another, and to the pillar-plate. 



Having defcribed the rack, and the parts connefted with 

 it, we will next in order proceed to the defcription of the 

 pinion C, and the hour and quarter ratchets N and O at- 

 tached to it, and alfo their mode of conneftion, by which the 

 hammers are raifed to caufe them to hit the blows, or to 

 Jlrilce. The larger of the two ratchet-wheels, N, the one next 

 the pinion, has originally been cut into twenty teeth, of which 

 twelve confecutive tielh are left ; then three more teelh, at 

 an interval apart from each other, and from the laft of the 

 twelve teeth, equal to the fpace of a tooth ; the remainder 

 of the teelh, that occupied the fpace from the laft of the 

 three to the firft of the twelve teeth, are taken away. The 

 upper ratchet, O, which afts on the fmall hammer, has been 

 originally cut into ten teeth, of which only four confe- 

 cutive 



