130 



HOROLOGY. 



Rewarils of- 

 fered for as- 

 certaining 

 the longi- 

 tude at sea. 



Debaufre's 

 'scapement 

 possesses an 

 advantage 

 over Gra- 

 ham's. 



Abbe] Hau- 

 tefeuille's 

 'scape- 

 ments. 



PLATE 

 CCCI1. 

 Fig. 5. 



keeper to ascertain the longitude at sea. In this at- 

 tempt he was not so successful in his first trials, as he 

 had led himself to expect. It was in general believed, 

 however, that had he lived he would have been the first 

 to have deservedly acquired one or other of the pre- 

 miums which were before that time offered by four of 

 the greatest maritime powers in Europe, to those who 

 should produce a time-keeper which could ascertain, to 

 a certain extent, the longitude at sea. Philip the Third, 

 who ascended the throne of Spain in 1 5Q8, was the first 

 who proposed a reward of 1000 crowns for this inven- 

 tion. The states of Holland soon after followed his ex- 

 ample, and offered 100,000 florins. The British Parlia- 

 ment, in the reign of Queen Anne, voted j20,000 ster- 

 ling for the same purpose ; and the Duke of Orleans, 

 Regent of France, in 1716, promised, in the name of the 

 King, 100,000 livres. Sully may literally be said to 

 have died a martyr to the cause in which he was enga- 

 ged. Having got a false address to a person who it was 

 said was occupied in the same pursuit with himself, he 

 got so overheated in his anxious and vain endeavours 

 to find him out, that he died in a few days after at Pa- 

 ris, in the month of October 1 728, and was buried with 

 great pomp in the church of St Sulpicius. Sully act- 

 ed so conspicuous a part in the profession, that no apo- 

 logy is necessary for giving this short account of him. 



It may be observed here, that Debaufre's 'scapement 

 has this advantage which is not in Graham's, that the 

 impulse is given the same in every vibration ; and the 

 time of rest on both sides is the same, bearing mostly 

 on the foot pivot end, and a little on the sides of the 

 pivots ; and not wholly on the sides of the pivots, as 

 in Graham's. Having made one or two watches, to 

 which this 'scapement was put, they were found to per- 

 form very well ; and we would recommend it to the at- 

 tention of 'scapement makers : A little practice will 

 make the execution of it very easy. The two thin steel 

 wheels may at pleasure be placed at any distance from 

 one another ; their diameters should be as large as can be 

 admitted between the potence foot and the verge collet. 

 An agate, or any hard stone for the pallet, whose height 

 is half the spaces between the teeth, or a little less, is 

 fixed on the verge or axis of the balance ; the level of the 

 base of the pallet on which the teeth rest being a very 

 little above that of the line of the centre of the balance- 

 wheel pinion. The teeth must be a very little under- 

 cut, so that the points only may rest on the pallet The 

 verge should be placed more inward in the frame than 

 in the common contrate wheel movement, in order to 

 give room for the balance-wheels. The necessity of a 

 contrate wheel movement for this 'scapement is a trifling 

 objection, which will wear away in spite of prejudice. 



In 1722, the Abbe Hautefeuille, who long before this 

 had at Paris disputed, in a process of law with Huy- 

 gens, the right of the invention and application of the 

 pendulum- spring to the balance of a watch, published 

 a quarto pamphlet, containing a description of three 

 new constructions of 'scapements for watches. One of 

 these was the anchor, or recoiling 'scapement, on the. 

 verge of which was attached a small toothed segment of 

 a circle, or rack, working into a pinion, which was the 

 axis of the balance. The idea of the axis of the ba- 

 lance being a pinion, seems to have been taken from the 

 'scapement of Huygens, with this difference only, that 

 the balance should not make so many revolutions as that 

 of Huygens, and is contrived so as to make scarcely one 

 revolution at every vibration. This 'scapement is the 

 same as it came from the hands of Hautefeuille, without 

 any improvement having been made upon it even to this 



day, although a patent was taken out for the same in- 

 vention above twenty years ago, by some person in Li- 

 verpool. The name of lever watches, which they re- 

 ceived from the patentees, is that which is generally gi- 

 ven to those having this 'scapement, which is the same 

 that Berthoud has described in his Esxai surL'horlogerie, 

 published in 1763; see torn. ii. No. 1933, and 'plate 

 xxiii. fig. 5, of which our Figure is a copy. Ber- 

 thoud, under certain modifications, introduced the prin- 

 ciple of this 'scapement into some of his marine time- 

 keepers. 



A very able and ingenious artist at Paris, M. Duter- 

 tre, who was zealous in his profession, and had consi- 

 derable success in his pursuits, invented, in 1724, a 

 new 'acapement, or rather improved that of Dr Hooke's 

 with two balances, which has already been described. 

 The additions and improvements, however, which he 

 made, were so great, as to give him a sort of title to 

 claim it as his own, and to render it, in the opinion of 

 good judges, the best 'scapement by far that was known 

 at that time. The additions which he made, consisted 

 in putting another wheel upon the same arbor with 

 the first, but it was considerably larger in diameter, 

 having the same number of teeth with the other, and 

 forming the principal merit of the 'scapement. The 

 balance arbors at one place were made rather thick- 

 er than usual, for the purpose of having notches cut 

 across them, and as deep as to the centre. This part 

 of the arbors becomes then a semicylinder. The lar- 

 ger wheel, which may be called that of arrcle, or re- 

 pose, is placed on its arbor, so as to correspond with 

 the semicylinders ami their notches, the points of 

 whose teeth are made just to clear the bottom of the 

 notches, alternately passing one of them, and resting 

 on the semicylindrical part of the other. The action of, 

 the two wheels shall now be explained. Let us sup- 

 pose, that one of the larger wheel teeth, after reposing 

 on one of the semicylinders, is, on the return of the vi- 

 bration of the bahuice, admitted to pass through the 

 notch ; after having passed, a tooth of the impulse-wheel 

 falls on the corresponding pallet, gives impulse, carrying 

 it on till it escapes ; when another tooth of the wheel of 

 repose falls on the other semicylindtr, and rests there 

 until the return of the vibration of the other balance ; 

 when it passes the notch in its turn, and the corre- 

 sponding pallet presenting itself, is impelled by a tooth 

 of the impulse-wheel, and so on. Hooke's 'scapement 

 had a small recoil ; the aim of Dutertre was to make a, 

 dead beat one of it, in which he succeeded There is 

 a drawing of this 'scapement in Plate xiv. fig. 4. of 

 Berthoud's Hisioire de la Mesure. du Temps. He says, 

 " that the properties of this 'scapement are such, that 

 sudden shocks do not sensibly derange the vibrations ; 

 that the pressure of the wheel-teeth of arretc on the 

 cylinders, corrects the impulse that the balance re- 

 ceives from the wheel-work, which, on the motive- 

 force being doubled, prevents the vibrations from being 

 affected." 



In Plate xli. fig. 16. of the first volume of Thiout's 

 work, is a drawing of this 'scapement, modelled for that 

 of a clock, described at page 101. He says, " Fig. 16. 

 is an escapement of the Sieur Jean Baptiste Dutertre, 

 which has only one pallet, on, the axis of which is the 

 fork.. The two ratchets or wheels are on the same ar- 

 bor, when the pallet escapes from the small ratchet ; 

 the larger one, which is called the ratchet or wheel of 

 arri'te, rests on the arbor of the pallet, and leaves the 

 vibration to be pretty free. On the pallet's returning to 

 meet with, the teeth of the small ratchet, the pallet-ar- 



Kcaj>e- 

 n;cnts. 



Dutertre't, 

 'scapement 

 for a watch. 



PLATE 

 CCCII. 



Fig. 6. 



Dutertre"* 



clock 'scape- 



man. 



Fig. 7. 



