HOROLOGY. 



143 



middle of tlus is a hole tapped, into which is screwed a 

 .-t uil, -landing at right angles to the arbor ; a be\ elled 

 wheel of 38, aivl diameter l.j inch with its socket 

 turns on this stud, which is placed on the arbor at that 

 distance, so that the two bevelled wheels may fairly pitch 

 into one another ; the minute wheel is uxx^d into tour, 

 and through one of the cross's openings, the bevelled 

 wheel B which is on the stud gets to pitch with the be- 

 velled wheel b which is above the minute one. On the 

 inside of the pillar plate is screwed a cock A, near 



ach in height, and so that the middle part of 

 the upper knaj shall be opposite to the lower end 

 and pivot of the minute pinion arbor. On one end of 

 another arbor in length about 2. 1 inches, having a shoul- 

 der on it, is rivetted a bevelled wheel c of the same 

 diameter and number of teeth a* the other* ; another 

 thanldfT of just a sufficient thickness is made on this 

 arbor at the back of the bevelled wheel ; the rest of the 

 arbor is nearly straight all the way, to the shoulder of 

 a pivot which i* at this end ; from this shoulder the 

 arbor is squared down for about .6 or .7 of an inch, to 

 receive the socket of a small wheel W of 32 teeth, which 

 turns behind the pillar plate ; this wheel i* nearly one 

 inch in diameter, and a cock K is screwed on the beck 

 of the pillar plate, in which the pivot of the wheel of S3 

 run* ; a pin u put through the socket and square, to 

 keep the wheel fast to its place on the arbor. When 

 the shoulder at the back of the bevelled wheel bean 

 on the outside of the kneed cock, which b on the 

 ineide of the pillar plate, the cock having a hole in it 

 which allow* the arbor to go through and to turn in it, 

 then the pivot of the arbor will run in the cock which 

 i* at the beck of the pillar plate. The inside bottom 

 of the bevelled wheel, which i* rivetted on the shoulder 

 of this arbor, ha* the end of the arbor made flush with 

 it, and a hole mad* in the end and centre of the arbor 

 to receive the lower pivot of the minute pinion, in 

 which it runs or turn*, the bevelled wheel which is on 

 the stud being supposed to be set as low down as it 

 thai! meet and pitch properly with that which i* at the 

 end of the other arbor. It will now be seen that the end 

 -hake of the** arbors, when combined, will lie between 

 the minute pinion cock on the fore plate, and that which 

 U e*t the back of the pillar plate. Let us suppose that the 

 bevelled wheel, which i* at the end of one of these arbors, 

 remain* a* it were stationary .rwl th&tth*ou> 

 and wheel are carried about by the minute pipe wheel, 

 which i* on the arbor of the centre wheel ; during a re- 

 volution of the minute wheel and pinion, the bevelled 

 wheel, which terms on the stud, will be carried not only 

 round with its stud, but i* made to make another revo- 

 lution by mean* of it* turning round on the teeth of the 

 bevelled wheel, which is Ketienery, cauting the bevel- 

 led wheel, and the flat wheel connected 

 are below the minute pinion, to make two revolution* 

 in the hour ; and a* the flat wheel of W teeth turns 

 the sun hand wheel of 76 teeth and -'. i inches in diame- 

 t make its revolution in an hour. Its soc- 

 ket turn* freely on that of the minutr pipe wheel which 

 carries the ind ; between the un hand wheel 



and this minute pip . a slender spiral spring, 



the inn-r end of which is fixed to the lower end of the 



wheel otket, the outer end being fixed in a stud on 

 the upper surface of the minute hand w her 1 This spring 

 is fvr the purpose of keeping forward the sun hand to its 

 place, notwithstanding any shake which may be among 

 the teeth of those wheel* concerned in the equation mo- 

 tion work. The win's hand j of brat* gilded, having the 

 figure of the sun on it, at a little distance from the 

 end which point* to the minute division*. The sun's 



Equation 

 Clocks. 



i lies bet \vtvn the hour and minute hands ; the wheel 

 of 70, which carries it, besides the motion of going once 

 round in an hour, has at one time a small motion retro- rj^cnpioa 

 grade, at another a small motion progressive, according to ,,, !Ln U)IU . 

 the equation ; and there are four times in the year when tion clock. 

 the minute and sun hands are nearly together. One 

 half nearly of the sun wheel is crossed out, on that side 

 in which the sun's hand lies, in order that the equili- 

 brium of the hand and wheel may be as nice as pos- 

 sible, whatever may be the position of the sun hand. 



From the centre wheel hole on the fore frame plate, 

 towards the U-lt hand, and a little upwards, take, with 

 a pair of compasses, a distance of 3.8 inches, and sweep 

 an arch ; and then from the centre of the hole, in which 

 the arbor runs, which carries the annual plate wheel, 

 take in the compasses an extent of 4.6 inches, and sweep 

 another arch so as to intersect the first, the place of in- 

 tersection will be that of an arbor having pivot*, one 

 of which runs into a cock, screwed on the back of the 

 pillar plate ; the other runs into a cock screwed on the 

 front of the fore frame plate ; a notch is made on the edge 

 of each frame plate to admit the arbor to come into iu 

 place. On the end of this arbor, which is just behind 

 the pillar plate, is fixed a rack or segment of a circle 

 5 inches radius, having 32 teeth cut on it, and cut from 

 a number on the engine plate of 318 ; the rack-teeth 

 - into the small wheel of 32, which lies behind 

 the pillar plate, .and whose centre coincides with that 

 of the minute pinion arbor, as mentioned before. < )n 

 the other end of this arbor, and beyond the fore frame 

 plate a very little, i- fixed an arm of 1.5 inches 1 

 Having at the end of it a smooth hard steel pin, which 

 bean on the edge of the annual elliptic equation plate, 

 being nude to do so by mean* of a coil or two of watch 

 main spring not very strong, attached to the arbor, near 

 to the inside of the fore frame plate, the outer en. I l>< - 

 ing fixed to one of the pillars, or to a stud fixed for that 

 purpose on the inside of the fore plate. The elliptic 

 equation plate is a very irregular sort of a figure, a* 

 may be conceived in some degree by the description of 

 its shape; its greatest length over all is 6 5 inches; the 

 centre is 3.8 inches from the broadest end, and 2.7 

 inches from the narrowest; the nearest edge across the 

 centre i* about one inch, and the edge opposite is 1.8 

 inch ; the greatest breadth of the broad end i* near to 

 inches, that of the narrowest end i* 2.6 inches. I)u- 

 e course of it* annual revolution, the edge of the 

 plate makes the arm which has the ^ti-4-1 pin in it 

 rise to various heights, and fall a* variously to dif- 

 ferent depth*. By this rising and falling, the rack which 

 u at the opposite end of the arbor, i* made to have a 

 motion sometime* backward, and at other times for- 



vhich it communicates to the small wheel <: 

 Ulnml the pillar plate, and of course to the !*. 

 wheel of 38 on the same arbor, with it. ThiscontimUlv 

 cause* a small change of place, to thel \,;:,,l u|, ,'| 

 of 38, consequently a change of place to that which 

 turns on the stud, and hence to the wheel carrying the 

 MIII hand ; thi* change is what give* the equation, 

 shewn by the difTrn-nce of time between the minute 

 and sun hand*. \Vh-n the pin in the arm 

 equation or sun hand goes forward, and who 

 gc* backward/ The greatest negative equaton for 

 181 j, on the 3d day of November, i* If; minute*, I4.y 

 second*, which, added to the v aion 



for the same year on the 1 1th of February, is Uminutes, 

 36.3 second*, making m all 30 minutes, 51.4 second*; 

 so that one tooth of the Iu 1 1 . ,:' 32 may be nearly 

 equivalent to one minute of equation. To tract- pro. 

 periy a true figure to the equation plate, must be a 



