HOROLOGY. 



135 



had nude, tlie 'scapement is on a very flattering prin- 

 ciple, which he had suggested as the means of im- 

 provement many years before be put it in practice 

 It* good p 



good performance seems to have been unequalled ; 

 _,__- and it is singular, that, notwiUutanding the efforts 

 aTarnntni, of three or four of the beat hands that could be got 

 to the establishment set up by Mr Mud c, junior, 

 in order to put these 'scapenients to time-keepers 

 which they were employed to make, not one was 

 ever produced that was at all equal to the original 

 ones. The 'scapement ia app-.reHtiy very complex, ela- 

 borate, and of course expensive in making ; yet, when 

 once executed, it will be permanent in it* effects, 

 and require no after adjustment like the common 

 detached one. After what has happened, it is not like- 

 ly that it will be again adopted. The basis of it is 

 that of the curious old crown wheel and verge. In 

 place of the verge being in one, having two pivots and 

 the balance rivetted on it. let us conceive that each of 

 the pallets of the verge has an arbor and two pivot*, 

 and that the balance ia on a double kneed crank, hav- 

 ing a pivot at the end of each knee, one l*ing near to 

 the foot, the other near to the collet on which the ba- 

 lance ia rivetted ; thete pivots, and those of the pallet 

 arbors, are in one upright line, coinciding and concen- 

 tric with one another, having their motion, as it were, 

 free and independent of each other, unles. when in a 

 pan of the action of the 'scapement ; the face of the 

 pallets, in place of being flat, are hollow, or a little 

 curved, having a nib at the edge to lock the wheel 

 by. On the lower end of the lower pallet arbor ia 

 n arm projecting nearly a* far a* the bending of the 

 crank knee, in which ia fixed a pin that acts on the inner 

 tide, and near to the end of the arm. and ia alternately 

 acted upon ; close by the arm. and on the pallet arbor, 

 the inner end of a spiral spring is fixed ; the outer end ia 

 in a stud, having a certain tension or bending up before 

 in the stud. The upper pallet arbor has the same 

 a* baa been described to the lower one, and a pin in the 

 upper knee of the crank. It may easily be conceived, 

 that the length of the crank knee* ought to be such a* 

 to allow h to sweep round and behind the crown wheel, 

 its boundary or banking being that of the crown wheel 

 arbor, or iu pinion arbor. When the pellets are not rais- 

 ed up, and the wheel unlocked, the tendency of the api>al 

 i to bring them down within the spaces of the 

 -.the upper pJletred up. 



ed up, and the wheel ia 

 the upper ann being ear- 



the right, 



the pin in the upper crsoik wul of conneneet with the 

 MO arm, and carrying h on a little way, the wheel- 

 tooth gets disengaged, bj which the wheel getting for- 

 ward. the lower pallet n raised 

 again locked. In the 

 ned on a few degree., by 

 the balance in vibrating, bend* up the spiral still more 

 than what was done by the wheel raising up the pallet, 

 he re-action of which in the returning vibration 

 impulse by mean* oflheannoalbepmofUtc crank. 



the lower crank now getting forward, meets 

 with the arm of Uw lower pallet arbor, carries 

 the wheel gets disengaged, and so OB. This -scape- 

 nent cannot act itself oT; for bttare this can be effected, 

 the balance moat get some degree of external circular 

 notion in its plane. The hahnce may be and to be 

 free in that part of the vibration, after the pin of one 

 crank baa left its corresponding arm till the pin of the 

 other meets with its arm ; this is, however, very mo- 



The balance had ou its arbor two spirals 



or pemlulutn springs, for the purpose of obtaining F.tefe~ 

 the most isochronous vibrations. Something in this ^""*^ 

 way had been proposed by one of the Bernoullis. """Y"" 1 

 Drawings and a description of this 'scapement will be 

 found in the work published in 1799, by Mr Thomas 

 Mudge, junior The compensation, like every thing 

 ot' M.I icr'v is ingenious; though nothing of this kind 

 can ever be equal to that of being in die balance itself. 

 The train of wheels went contrary to the ordinary di- 

 rection, and we have no satisfactory reason assigned for 

 it. 



Although the balance in pocket watches may be put 

 very well in equilibrium, yet many things contribute 

 to make them go unequally in different positions, such 

 as in hanging, laying. Sec. which require time, and give 

 a great deal of trouble, before they can be completely 

 corrected. In order to get the liettrr of thin, Breguet, BrcgU4| ., 

 an eminent watchmaker in Paris, contrived a 'scape- revolving 

 ment, which, with the pendulum spring stud, revolved ' 

 round the centre of the balance once every minute. 

 By this means, whether the balance was in equilibrium 

 or not, the going of the watch was little affected by it, 

 aa every part of it was up and down in the course of a 

 minute, which compensated any want of equilibrium. 

 This contrivance is merely mentioned by Berttumd 

 in his Hutoirr, a* he did not think himself at liberty 

 to give any description of it, since Breguet had a 

 patent or tret** finmtmrn to make them. We have 

 Liard it said that the same invention had been made 

 before by the late Mr John Arnold. 



Those who wish for farther information respecting 

 'arapemenu, may consult Trattc Horiogerif, per M. 

 Thiout, Hutoirf oV la Meture dm Trmpt, par M. F. Ber- 

 thoud. and the 7Vsuec*MM oftke Socittyfor the . 

 of Arit, Cummrrct, <$r. 



HAP. II. 



On 



CaWPBX%TioM against the effects of heat and cold in Onibeeoaa. 

 tienkaiinri. baa been one of the great et improve- pcnuuioa 

 menu that could have been applied to them. u ilhout " 

 Una they would have been far from keeping time, and 

 weald have varied continually with the temperature of 

 r, so that no ixed or settled rate could have 



The detached 'scepament ,l) 

 thi* more than any other : for if there is no i 

 tion to it. the watch will vary nearly thirty seconds in 

 t went v -four hours. The influence ef oil on the cylinder 

 'st.ptieent buas in itself a sort of compensation, 

 .e effect of cheng*. of temperature is much lew 

 obvNnis in it than in the detached 'srapemcnt. There 

 it very great reason to believe that Harrison was the 

 first who applied a compenaation ; but there are no 

 written documents to warrant us in ascribing to him 

 the honour of the invention, to which, however, we 

 think he hasajut title. Some very imperfect hints 

 had been given liy Martin Folkes. Esq. President 

 Hoyal Society in the year 17*9. of Harrison'* 

 having tome mechanism of thi* sort in the three time- 

 pieces huh had licen made prior to the fourth, which 

 gained the reward voted by parliament. But as no 

 deacription of it was ever made public, the Fm>rh ar- 

 tists have bad it in their power to claim a priority in the 

 invent 'n. In H.irri-n' fourth machine, it is known 

 tl. it the compen ation piece in it was composed of la- 

 minae of bra** and steel pinned and rivetted together in 



