71* 



HOBOIiOBT 



HOROLOGY. 



the band. The whole of the wheels in this group can therefore be 

 turned forwards or backward* without disturbing the internal media- 



Fiun.wbnl. 



nism of the clock, or rather that part of it which is called the </ 

 vatfk train ; for the minute-wheel a gives motion to another minute- 

 wheel It, which, as it must revolve also in an hour, has the same number 

 of teeth as u. A pinion in the centre of the wheel 6 luw six leaves, 

 nnd acts in the hour-wheel c of 72 teeth, which is placed over the 

 minute-wheel a, and consequently revolves once in 12 hours, and has 

 screwed to its socket, at the upper end, the hour-hand. To the socket 

 of the hour- wheel, about one-eighth of an inch above the wheel, is 

 fixed a piece in which are 12 steps, each of which includes an angle of 

 30, or a twelfth part of a circle ; this piece is called the mail, and is 

 represented by d. t is a rack whose centre of motion is a stud or pin 

 /, on which it acts by means of a pipe about half an inch long, and on 

 to the upper end of which is riveted the rack-tail y ; in this rack-tail IB 

 a short pin A, pointing perpendicularly downwards to the front plate 

 of the clock. The rack lies about the tenth of an inch above the front 

 plate ; but the pipe which acts on the stud is long enough to carry the 

 rack-till just clear of the snail when the rack is forced back by the 



r' tig i ; whilst the pin A is long enough to strike against the steps in 

 mail, and yet so short as to be perfectly free of the hour-wheel c. 

 Near this U t, the rack-hook moving freely on a stud ; in the lilting 

 piece, also moving freely on a stud p ; n the tail of the lifting-piece 

 firmly pinned on to the upper part, and moving with it ; o the gathering 

 pallet, which has a square hole through it, and is fixed upon the square 

 end of the arbor q of the wheel g (fg. 4) which revolves once for every 

 blow given by the hammer. A pin in the warning-wheel A always 

 stands in the same position when the striking part is at rest, which is 

 the position represented in fy. 4. On the end of the lifting-piece is a 

 small piece q (Jiff. 5), which passes through a slit in the front plate, 

 and resting on the bottom of the slit, keeps the lifting piece in it* 

 proper position. The gathering pallet o rests on a pin r in the rack, 

 and thereby prevents any motion in the internal wheel-work of the 

 striking train. Such being the mechanism, the mode of action will be 

 understood from a study of the figures, without a detailed description. 

 A small piece x is called the putt-pita, by pulling a string at the end 

 of which the lifting-piece is raised, and the clock is made to repeat 

 the hour last struck at any required time, y is a spring to force 

 the pull-piece x against the pin 2 fixed in the plate of the clock ; is 

 another pin to limit the motion given to the pull-piece .r when the 

 string ( is pulled. 



Pocket-u-atcha. Without attempting to notice the numerous im- 

 provements in spring clocks, we shall proceed briefly to describe those 

 features in a pocket w-atch which are of a distinctive 

 character. 



When clocks and watches had acquired a certain 

 degree of accuracy in their performance, the time lost 

 in winding up (especially when it had to be done 

 every twenty-four hours) became a matter of import- 

 ance ; and there have been several inventions to 

 remedy this evil, by pnxlucing what is called a main- 

 i poKtr. By Huyghena the clock wa kept going 

 while winding by means of an tndlni cord, as it 

 B is the clock-barrel; c, that portion of the line \\}m -h 

 comes from the barrel to the weight ; r, a pulley for 

 the line to run over ; <J, a pulley for the line to run 

 under, and to which is attached a small weight < 

 will be seen by inspection that the baud applied to 

 that part of the line marked a will be able to raise 

 the weight w without depriving the barrel B of any 

 portion of the power by which it is urged forward, 

 and which power in this arrangement in equal to one- 

 half of the weight W. Another kind of maintaining 

 power is the forcing if ring, shown in f<j. 8. A lever A, 

 whose centre of motion is o, has a notch cut in its 

 end, into which is jointed a small lever c, whose centre 

 of motion is x; this small lever is kept in it.- p. ] r 

 position against the bottom of the notch, as shown in 

 A, and also in B (which is only another position of the lever), by a 

 Might spring . D is a strong spring which acts constantly on the 



Fir. :. 



Endlrw Cord. 



lever A, having a tendency to force it into the position represented 

 by B, in which it U not in action. Previous to winding the clock up, 

 the end t of the lever is depressed and brought from position n tu 



i -. -. 



Fotclng-sprinp. 



that of A ; and in its progress in passing a tooth of the wheel the small 

 lever r assumes the position represented in Jig. 9, which it is allowed 

 to do by the very slender spring i. As soon as the tooth is passed, 

 the pressure of obliges the lever r to return to its original place ; 

 and by the pressure of its opposite end on the bottom of the notch in 

 which it is inserted, the lever A is prevented from regaining its former 

 position by the pressure of the piece e on the tooth of the wheel 

 until the wheel shall have advanced so far as to have allowed its 

 escape, when the lever regains its jo.*itii.n , where it remains till 

 another winding becomes necessary. It will IK- ivM.nt that so long 

 as e remains on a tooth, the wheel will be urged forward by the action 

 of the spring D. e e are two pins which are fixed in the plate of 

 the clock, and serve to determine the quantity of motion given to the 



le\er A. 



Harrison's contrivance for the same purpose, however, is the one 

 now in general use, both in clocks and watches, and is admirably 

 adapted to the purpose. When this principle is applied to a fusee, it 

 U termed a going ftuee ; but maintaining power, as a more compre- 

 hensive term, is now generally applied. Into the hollow of the fusee- 

 wheel is placed a circular spring 4 c, (Fig. 1"), which i secured to 





Fig. 10. 



ll.irriion's Maintaining; Power Going Fusee. 



1, l-'ucee auxiliary rutchct, and fu-wheel attached ; 2, fusec-whefl and 

 auxiliary tpriug, wparmte ; 3, 4, upper and under oidci of the fu*cc, 

 separate ; 5, auxiliary ratchet ?, with clicki n a, and s;>ringi> e e, attu< In .1 . 



the wheel by a pin at about one-fourth of its circumference from the 

 t-nd (i, namely, at 6. The wheel has a short notch cut through it, 

 nrar the other end of the spring. The spring passes over this notch ; 

 and by means of a pin r, fixed firmly in the spring ami projecting 

 through the notch in the wheel, a motion is allowed to the spring, 

 which in extent is equal to the difference between the length of 

 the notch in the wheel and the thickness of the pin which passes 

 through it. It is the reaction of this t-pring through the short 

 distance already mentioned which maintains the motion in tin 

 during the time of winding up. Instead of any click anil 

 attached to this fusee-wheel, as in an ordinary eight-days' clock, 

 is a circular disc of steel, rather larger than the bottom < t -I, 

 and smaller than the fusee-wheel, having very fine ratchet-teeth cut 

 in its edge, and two clicks a a and springs e e on its upper surface, in 

 which the ratchet fixed on the under ride of the fusee, and called 

 the fusee-ratchet, acts. The steel-ratchet is called the auxiliary-ratchet, 

 and iU teeth stand in a direction opposed to those of the fusee -ratchet. 

 We will now suppose the auxiliary ratchet to be laid on to the fusee- 

 wheel over the spring a b r / a hole in its centre passing over a short pipe 

 in the centre of the fusee-wheel retaining it in its situation ; the pin 

 f, which we have described as projecting through the notch in the 

 fusee-wheel, also projecting upwards just equal to the thickness of the 

 auxiliary-ratchet, through which it likewise passes ; and the piu exactly 



