140 



HOROLOGY. 



Winding. 



Mr Reid's 

 hux chroao. 

 jnvti-r with' 

 out I'us.v, 



spring, or 



Millinery ratchet wliich rested on the first wheel, where the click 

 tor -r ing a]1 ,i spring w.1s placed to act with the ratchet, which by 

 '' the hollow socket allowed the pinion to turn freely 

 backward when winding up; on the weight being al- 

 lowed to act on the rack, all the wheels were made 

 to turn the proper way, and so on. An idea occurred to 

 us, that, in place of the rack moving, a machine might 

 be made to go by its own weight, by means of a pi- 

 nion turning down on the toothed edge of a fixed rack. 

 A scheme shall be given for a box chronometer of this 

 construction, which supersedes the necessity of either 

 fu-.cc. barrel, spring or chain. A contrivance of a si- 

 milar kind, has lately been communicated to the Socie- 

 ty of Arts in Paris, by M. Isabelle, and is described in 

 the Bulletin de la Socicti' d' Encouragement, No. 52. 

 The same method, which has been known for a consi- 

 derable time, is used at Liege by Hubert Sarton, who 

 makes eight day spring clocks on this plan. 



On the arbor of the first or great wheel, is fixed what 

 may be called the fusee ratchet, working with the click 

 and spring, which are on the auxiliary or going ratchet ; 

 in the last is fixed a pin, which comes through the end 

 of the auxiliary spring, and the circular notch in the 

 great wheel, which is keyed on in the same way as in 

 the case with a fusee; and having also a detent and 

 spring for the going ratchet, the whole forming the great 

 wheel, and the mechanism for going in time of wind- 

 ing. On the great wheel arbor, close to the main 

 ratchet, let a small bevelled wheel be fixed, of any small 

 number of teeth, fully stronger than those in the great 

 wheel, the back of the bevelled wheel lying against 

 the main ratchet : indeed both might be made from one 

 and the same piece of brass. Supposing the diameter 

 of the pillar plate to be 2.25 inches, that of the great 

 wheel would be 1.5 inch, and the number of teeth 72; 

 the bevelled teeth being half an inch in diameter, would 

 admit Jt teeth; and if made a little thicker than the 

 great wheel, the teeth would be sufficiently strong. 

 Another bevelled wheel, of the same diameter and num- 

 ber of teeth as the other, is fixed on a pinion arbor, (a 

 hole being made in the potence plate, to allow ihf bevelled 

 wheels to pitch together,) which is placed within theframe 

 in a horizontal direction, in that line which passes through 

 the centres of the great and second wheels; one of the 

 pivots runs in a cock inside of the potence plate, and 

 placed near to the great wheel arbor ; the other, which 

 is a little beyond the pinion head, runs in a cock fixed 

 on the outside of the potence plate. This pinion has six- 

 teen leaves of the same strength as the teeth of the 

 bevelled wheels, and runs in with the edge of a toothed 

 rack ; every revolution will be over the length of one 

 inch on the rack, and equal to four hours, or one turn 

 of the great wheel ; the second wheel pinion being 1 8. 

 The length of rack supposed to be 8 inches, would 

 allow the time of going to be equal to 32 hours, 8 

 inches multiplied by 4 being equal to 32. Were the 

 rack 12 inches long, it would admit the time of going 

 to be 48 hours ; or the diameter of the pinion might 

 be increased from .333 to .500 parts of an inch, and 

 the time of going would then be somewhat more than 

 30 hours. Let a slip of wood be made 15 inches long, 

 ths of an inch broad, and rather more than |th thick, 

 on one side of this, and close to the edge, let another 

 slip of the same dimensions, but not quite so broad, be 

 set on edge at a right angle to the side of the other ; 

 this will form a pattern to have two such cast in brass 

 from it ; after being dressed up, one is left plain, the 

 Other so as to have twelve inches of teeth made on one of 

 the edges ; the plain one is screwed to the inside of the 

 case, and the other is screwed on to the plain one, having 



the toothed edge on the right hand side of the pinion, so Machinery 

 as to make the second wheel and pinion turn the proper f or 

 way. To the ring or cap which incloses the move- 1 x ".. tl ".'. e "' 

 ment of the chronometer, arc attached three pieces -_ ''^'- 

 of brass, kneed up st_ each end ; the distance from 

 the ends is about two inches and a half, in which are 

 liolfs made quite parallel to one another, and go on 

 three steel rods, 1 5 inches long and t^ths of an inch 

 in diameter, fixed in the lower and upper ends of 

 the case, and parallel to one another, and near to 

 the dial of the chronometer. The case may be either 

 of wood or brass, having a door on one side, which 

 serves the purpose of getting at the chronometer, ei- 

 ther to observe the time, or to push it up after it is 

 nearly run down. In the lower part of the cap, a recess 

 may be made to receive any additional weight requi- 

 site to load the chronometer with, in order to give 

 greater extent of vibration to the balance; the upper part 

 of the case should, if necessary, be hung in gimbols, 

 and the lower end loaded with lead to keep it steady. 

 A chronometer might be easily fitted up in this way 

 to go eight days, by giving more length of rack, a, 

 greater weight to the bottom of the cap, more teeth to the 

 bevelled wheel which is on the horizontal pinion arbor, 

 fewer to that which is on the arbor of the great wheel, 

 and the second wheel pinion to make more revolutions 

 for one turn of the great wheel. Suppose the great 

 wheel 80, and the second wheel pinion 16, one turn 

 will be equal to five hours ; the bevelled wheel which 

 is on it (being 16) will have a revolution also in five 

 hours ; the bevelled wheel which turns it, having 24 

 teeth, will make a revolution in seven hours and a half. 

 The rack being 25.6 inches long, the pinion of 16 ma- 

 king a revolution on it in seven hours and a half, and 

 25.6 X 7-5 = 192, the number of hours in eight days. 

 The length of the case, being thirty inches, could be 

 no inconvenience where eight days going without 

 winding is obtained. A similar, and -we think a 

 preferable, construction might be adopted, by having 

 the chronometer fixed, and a weight hung to the lower 

 end of the rack, which, as in the case of a jack, would 

 keep up the motion required for the chronometer. This 

 plan, however, of a moveable rack, would require a 

 space for the rack to move in equal to twice its length. 



CHAP. VI. 



On the Dividing and Cutting Engine. 



AMONG the inventions in the art of Horology pro- Dividing 

 duced in this country, may be mentioned that of the and cutting 

 wheel-dividing and cutting engines, which are said to engiaes. 

 have been invented by Dr Hooke. In the preface to 

 the fourth edition of Derham's Artificial Clockmak- 

 er, he remarks, that " the invention of cutting engines, 

 ( which was Dr Hooke's, ) fusee engines, and others, 

 were never thought of till towards the end of King' 

 Charles the Second's reign." It is well enough known 

 that he contrived and used an endless screw and wheel 

 for-the purpose of dividing astronomical instruments, 

 in 1664. The wheel- cutting engine was contrived by 

 him in 1655 ; and, about the same period, he discover- 

 ed that the barometer indicated changes in the atmo- 

 sphere, and was connected with the weather. Ten 

 years afterwards, he proposed a clock to register the 

 rise and fall of the barometer, which was executed by 

 Mr Cuming, in a clock made for his present Majesty. 

 Sully carried over to Paris, wheel-cutting engines, 

 which were much admired there, not only for their 

 S 



