142 



HOROLOGY. 



1 'illation 

 Clocks. 



Description 

 of an equa- 

 tion clock. 



Moou's age, 



Lunar 

 phases. 



On the 

 moan's 



"lotion. 



socket, to fevolv'* on it freely and easily. The moon's 

 age ring turns within the annual plate ring, and is 

 divided into 59 equal parts, numbered 3, 6, 9t * n( l so 

 on to 29,',- Its diameter is five inches and one-eighth; 

 its breadth fully three-eighths of an inch, and it is 

 connected with a plain wheel neatly crossed into six 

 arms, of the same diameter and breadth of rim as the 

 moon's age ring, having six small pillars, nearly an 

 inch in height rivetted into it, and the moon's age ring 

 screwed at the opposite ends of three of them, by three 

 sunk steel screws. This plain ring has a socket, which 

 runs or turns on the stud, above the annual plain wheel ; 

 the face of the moon's age ring comes flush up with 

 that of the annual plate ring, and both come up to the 

 back of the dial, in which an opening in the arch is 

 made, in order to show a great part of what is on these 

 rings. From the top of the arch, across the opening, 

 and down in a straight direction, is stretched a very 

 fine wire, serving as an index to the days of the year, 

 the moon's age, &c. The annual plate ring and the 

 moon's age ring move or turn from the right to the 

 left hand, yet separately and independently of each 

 other. On the inside shoulder of the socket of the 

 moon's age ring is screwed a small bevelled wheel, 

 having 37 teeth, and one inch in diameter, the use of 

 which will be afterwards explained. In the dial is a 

 circular opening of one inch and three quarters in 

 diameter, a little below the opening in the arch ; in 

 this opening is exhibited the lunar globe of an inch and a 

 quarter in diameter, made of brass and silvered ; one 

 half of it is perpendicularly painted black, in order to 

 give the phases, the new and the full moon. On the 

 arbor of the lunar globe are two wheels, one of 63 teeth, 

 and about an inch in diameter, the other a bevelled one 

 of the same diameter, and with 37 teeth. Both are 

 placed below the lunar globe; the wheel of 37 and the 

 globe are fast on the arbor, the wheel of 63 being keyed 

 spring- tight above the bevelled one. The arbor of the 

 lunar globe is in the plane of the dial or nearly so, and 

 this bevelled wheel takes or pitches into that of the 

 same number, which is screwed on the moon's age 

 ring socket as before mentioned; and by means of 

 holes in the ring, the whole, that is, the globe, the 

 bevelled wheels, and moon's age ring, &c. can be 

 made to turn together, when the moon is at any time 

 setting to its proper age. The pivots of the lunar globe 

 arbor run on cocks which are screwed on to the back 

 of the dial. Behind the globe, and at a little distance 

 from it, is screwed on to the back of the dial, a sort of 

 concave or hollow hemisphere of thin plate brass, paint- 

 ed inside of a sky blue colour. 



We shall now proceed to show how the moon's mo- 

 tion is produced. On the top of the month nut socket, 

 where it lies in the plane of the dial, is cut a right 

 handed double endless screw, working into a small 

 brass wheel of 15 teeth, which is on the lower end of 

 a long arbor, standing upright in a slit made in the 

 dial. This slit is covered by a large circular silvered 

 plate, on which are engraved the hours, minutes, and 

 seconds; on the upper end of this long arbor, is a pi- 

 nion of 8, which carries about the wheel of 63, and 

 with it, at the same time, the bevelled .wheels, globe, 

 and moon's age ring. The pivots of the long upright 

 arbor, run in small cocks attached to the back of the 

 dial. The month nut, or hour wheel socket, makes a 

 revolution in twelve hours, carrying the hour hand. 

 The revolution of the moon's age ring is made in 29 

 days, 12 hours, and 45 minutes. The wheel of 63 and 

 : i 5 being multiplied together, the product is 945, and this 

 divided by 8, the number of the pinion, gives 118.125 

 times six hours, which being reduced gives the lunation, 



or a revolution of the moon's age ring as above, of 2i> Kquation 

 days, 1'J hours, 45 minutes. The time of the revolution (,'lucks. 

 may be made out by another wy- It is evident that 

 one tooth of the small wheel of 15 is turned every six 

 hours, of coursr *'^ wheel will be made to have a re- t ion clock 

 volution in 90 hours, and so will the pinion 8. Then 

 If we say as 8 : 90 : : 63 : 708.75 hours, which is also 

 equal to the given lunation of 29 days, 12 hours, 45 

 minutes. To produce the annual motion of the ring 

 plate wheel of 365 teeth, the month nut is cut into 

 42 teeth, and makes its revolution, as was said 

 before, in 12 hours, and turns a wheel of 84, con- 

 centric with which is a pinion of 8, leading a wheel 

 of 96, having concentric with it a pinion of 12, leading 

 the wheel of 365, which is the plate ring circle, having 

 on it the days and months of the year, the degrees of the 

 ecliptic, &c. turning once round in 365 days. Now as 

 365 X 96 X 84=2943360, this product, divided by that 

 of 42 x 8 x 12=4032, will give 730 times twelve hours, 

 or 365 days. The pinion of 12 is put on a square, 

 which comes in and through a small hole in the large 

 silvered circular plate; the wheel of 96 is put on a 

 round part of the arbor just below the pinion, and is 

 keyed spring tight on it ; by means of a small key 

 which fits the square, to turn the pinion, the annual 

 wheel of 365 teeth can be set to any required day of 

 the month, which can be done without disturbing any 

 of the motion-wheels. The setting of the moon's age 

 ring is equally free as this is from any disturbing 

 cause. The diameter of the month nut wheel of 42 is 

 one inch, and three and a half tenths of an inch ; that 

 of the wheel of 84 is 2.5 inches, and near to a tenth 

 and a half more. The wheel of 96 is three inches ; 

 its pinion of 12 is .307 of an inch, the pinion of 8 is 

 .316 of an inch in diameter. 



The minute pipe-wheel of 56 teeth, and 1 .8 inch in 

 diameter, runs on the arbor of the centre wheel, car- 

 rying the minute hand. It turns in the common way, 

 the minute wheel m of the same number and diameter, 

 whose centre lies nearly under that of the other, about 

 .6 of an inch to the right of the middle line of the 

 fore frame plate, and 1.7 inch from the centre of the 

 minute hand wheel. The arbor of the minute wheel 

 has a pinion of 8 leading in the common way the hour 

 wheel of f)(i, whose diameter is 3.25 inches, that of the 

 pinion is .426 of an inch. This pinion of 8 is put on the 

 arbor, by means of a square, and with the minute wheel 

 both are fast on the arbor. See Plate CCC IV. Fig. 7. The PLATE 

 upper side of the wheel may be distant from the lower ccuiv. 

 face of the pinion about .7 of an inch, the lower side hav- **& 7 * 

 ing a proper freedom of the fore-plate. Two wheels, one 

 a plain wheel of 38, the other a bevelled one of 38, hav- 

 ingthe same diameter 1 .2 inch, are screwed together, and 

 on a socket common to both ; the flat wheel is the up- 

 permost, and is pretty close to the back of the bevelled 

 one, whose teeth look downwards ; their socket turns 

 on the minute wheel pinion arbor, between the lower 

 face of the pinion and the upper side of the minute 

 wheel, having a proper end shake between them ; the 

 back of the flat wheel of 38 is below the lower face of 

 the pinion .4 of an inch. These wheels of 38 can be 

 made to turn on the minute pinion arbor, independent 

 of it and the minute wheel. The minute wheel and 

 pinion arbor extends a little way beyond and below 

 the minute wheel, perhaps one inch and three or four 

 tenths more to the end of its pivot ; it extends also be- 

 yond the face of the pinion more than .6 of an inch to 

 the end of its pivot, which runs into a cock C screwed on 

 the fore frame plate. There is a part formed on the 

 arbor of a flat circular shape, and whose thickness is ra- 

 ther more than that of the diameter of the arbor ; in the 



