HOROLOGY. 



127 



The old 'gupTMent, even after the application of the 

 pendulum-spring, not giving that satisfaction which was 

 required, induced Huygene and Hooke to think of other 

 means of improving it, or to substitute a superior me- 

 chanism in its place. In thix pursuit, the mechanical 

 talents of Hooke stood conspicuously eminent over those 

 of the justly celebrated Huyprns. 



Some of the movements af Huygens' watches. 



keepers, were much larger 



times* 



*** 



flAtt 







*';,-. : 



or 



than those of our box 

 The contrate wheel was cut into teeth 

 of the sane form as those of the common crown wheel, 

 and made to 'scape with a verge of the usual kind. On 

 the axis of this verge was a sort of contrate or crown 

 * wheel, having teen hke the ordinary contrate wheel, 

 which drove a pinion fixed on the axis of the balance. 

 The verge, when 'leaping with its wheel, caused the 

 balance to make several revolutions from every impulse 

 on the pallets. Some of them had no pendulum- spring, 

 having been made perhaps before hs application. When 

 the balance made several revolutions in every vibration, 

 each being two seconds, this 'scapement would be bat ill 

 suited tor the ceshof a pendalanviprin?. Those having 

 the imndiaVfni lui ing appeared abo>,' -.is was the 



origin of harf- timing, upon seeing, when the pendulum- 

 was applied, that it made the balance git 



in the same time that it gave one without it. 

 About the SHOO period, Dr Hooke brought into notice 

 his watch with a new 'sceperoent ; which, for stuntoen 

 *?*"' yean before, he bad been^ privately endeavouring to 

 unprow. Inn WeW Tfjry oHNfVtfit IFOOI Uiv ot<J cw>wn 

 wheel one, and aa nracn so from that of Hmrgens. It 

 had two balances, en the axis of each of which was a 

 toothed wheel, nitchnag into one another. The verge 

 or axis of the.'e balances had each a pallet on it. The 

 wheel waa flat, having a few ratchet or saw-like 

 hs arbor ran in the frame, parallel to those of 

 at a point equally distant from them ; the 



Iformms: . as it were, the angles of an eqni- 



W hen a tooth of the balance- 

 i on one pallet, the other, by the pitching 

 of the two wheels, was broagbt ahoot to meet another 

 tooth, (after the wheel had escaped from the pallet on 

 side, J in order to reeer** kwpnlse in hs 

 i pendetua. ipring on one of th. 

 and the object of their being pitched together waa 



rfeeb of external motion en them, while it 



HW. . 



the pallets, which still gave 



the rea.tion <!',- S.Ui.rr. 



ingenious contrivance for a 

 not to have given that 



" i* /_*_aV_t.l_ * 



n . pr-'fi- 



Sally's 



the 



recoil to the wheels by 

 Although this wa. . very 

 sent, yet h appears 

 wnfcn waa expected 

 it execution, which, 

 ,) and the old one was 



-^ whom wa* DMMlie, ware attracted by 

 it 'feapement of Dr Hooka's, and were led, from time 

 to time, to make impiimmian on it. From it origi- 

 nated the duplex 'scapement, which has of late years 

 been so much hi repute. A large old German dock 

 had a 'scaponent on the same principle as the above, of 

 which the maker's name ia unknown. Dr Hooke'. claim 

 to hi* own 

 The fanwue Tonmion. who nl i I greatly to 



bring the art of Horoh 

 potation which it had 

 sixty years or 



saM 



the lasjann waa a 



England to th 



for a long period of 



ifh he ,,rart,.| ,t, 



The verge or axis of 



across at the middle, and nearly h*?f>ay down ; along 

 the length way of this p:irt ( it deep angular 



notch was made, forming a sort' -of JMlJrt on the right 

 hind side ; the balance wh. -. n-l much like 



DrHooke's; and the spaces betuwn the tetth suffi- 

 ciently wide to allow the cyliixltr to turn freely l>etween 

 them. When a tooth of the wheel impelled the pal- 

 let, and when on escaping tr<xn it. the tooth following 

 dropped on the outside of the cylinder, neir the left 

 edge, resting on the cylinder drrin'.Mh>:- vil>r:ition of the 

 balance, after passing the It! d meeting .1 little 



recoil, rt got on the pallet, and gave n new impulse, 

 which was given only at every second vibration. An 

 excellent property was observed fti this Vapement, that 

 any inequalities in the motive force made no deviation 

 in its time-keeping ; hut the frirtiim of the balance 

 wheel teeth on the cylinder and in edges was so great 

 and destructive, that it \v.m given up in consquence of it 



Knowing what Tompion hud been doing, \te\ng bred Graham ' 

 under him, Graham, a good many years after, set to 'ietperorot. 

 work with the cylinder 'scapement, and ultimately P-* T 

 succeeded. Although this 'scapement is now pretty CC L 1 ' 

 generally known, yet we may be allowed to give an * 

 account of what he did. In place oF Tompion *s solid 

 cylinder he made a hollow one ; on the points of the 

 wheel teeth of Tompion were raised something like 

 small pins or sjem, on the tops of which a sort of in- 

 clined or curved wedge-like teeth were formed, of such 

 a length as to harte very IHtle freedom when in the 

 leof the cylinder, and the ontside of the cylinder t.> 

 have the aatae freedom between the point of one tooth 

 and the heel of the ether. A notch i>r opening was made 

 acrnaa the cylinder, not quite halfway down the dia- 

 meter ; the edges of the r> Imder made by this opening 

 were dress ui M> that the curved edjje of the tooth might 

 fUtasi aatiry en them ; the rig' .ownsflanched 



outward, the left one rounded ; when thr |..i];mce was at 

 rest, and the wheel in its place to 'scape, the point of the 

 tooth got then just in on the cylinder edges, and no 

 morr ; a second notch was made below the other, to 

 allow the bottom .>*' the wheel to pa**, leaving hardly 

 a fowrth of the circumference of the cylinder, the other 

 le\ ing more than a semicircle. The highest part of the 

 wedge or curved tooth being on a circle, greater or be- 

 yond that on which thr point w :hat, if 

 the wheel is urged forward, it will makr V r to 

 turn, and the angle of Vapement will be according to 

 the height of the wedge : When a tooth of the cylinder 

 wheel ecapes from the left edge of the cylinder, the 

 point of it tails into the imide of th. ~ : ,f:,T re- 

 posing there, and then pawing and impelling 

 nd enge ; on escaping it, the point of the uccv 

 tooth drops on the outsi.l >r, where it re- 

 poses ; on the retnm of the balance, it get-s on the left 

 hand edge, giving a new impulve, and o ..n The 

 teeth impel at both edgr of the cylinder, giving by 

 each vibration to the balance. 



'scapement being the bent 

 ceded it, (Debaufre's perh*i 

 (raham's watches a very consid< 

 their performance was much up 

 ef the old Construction. However, on comparing the 

 going of some of Graham's with thoe of a later 

 date, we confess that none of his, though exrellrnt, 

 were ever equal to them in this. Tne cylinders 

 were rather large in dinmetrr, the l>aUncr too light, 

 the motiv weak, ,-i d he had great itiffi- 



culty in obtaining good | , n g wire, meet- 



ing sometimai with iron, where he expected steel 



inv that hail pre- 

 rd) procured for 



le reputation, a* 



to that of those 



