194 CATALOGUE. PHILOSOPHY AND ARTS, PRACTICAL MECHANICS. 



Massey's escapement for clocks. S. A. XX T. 

 414. Nich. VIII. 161. Ph. M. XVIII. 305. 



The scape wheel of Arnold's and of Earnshaw's pocket 

 timekeepers has 15 teeth: those of the box timekeepers 13. 

 Arnold makes the impelling teeth of the scape wheel cy- 

 cloidal, acting against a point. His detent unlocks in- 

 wards, or towards the axis of the wheel ; Earnshaw's out- 

 wards. 



Pendulums and Balances. 



Paufre's watch with a balance making se- 

 veral revolutions. A. P. I. 288. 



Leibnitz's proposal for regulating motion by 

 springs alternately wound up. Ph. tr. l67 J. 



X. 285. 



Lahire on second pendulums. A. P. 1715. 



130. 

 Derham's experiments on pendulums. Ph. tr. 



1736. XXXIX. 201. 

 Euler on a new kind of oscillation. C. Petr. 



XI. 128. 



Rivasi on a pendulum moving in small arcs. 

 A. P. 1749. H. 182. 



Godin's watch with a double balance. A. P. 

 1754. H. 140. 



Grenier's pendulum. Roz. XVI, 139. 



Magellan on the advantage of a large vibra- 

 tion. Koz. XX. 376. 



Crossthwaite's pendulums. Ir. tr. 1788. II. 7. 

 Repert. III. 254. 



One of them supported by a diamond, 



Mackay. Enc, Br. Art. Pendulum. 

 Atwood on the vibrations of watch balances. 

 Ph. tr. 1794. 119. 



An isochronous combination of springs. Approves 

 Mudge's escapements. 



Leslie's patent short pendulum. Repert. II. 91. 

 Benzenbergon a centrifugal pendulum. Gilb, 



XVI. 494. 



For avoiding the alternation of motion. 



E. Walker on the effect of the arc of vibra- 



tion of a pendulum. Nich. 8. II. 76. 273. 



III. 35. 

 Hardy's mode of banking or checking the 



motions of a balance, S. A. XXII. 311. 

 Length of the pendulum. See Geography, 



and Rozier's Index. A. P. Art. Pendule. 



For every minute that a clock varies in a day, a second 

 pendulum must be altered -^ or .054 inch ; a half second 

 pendulum, ^ or .00134. 



Bernoulli observes, that the time of vibration in a circular 

 arc may be found very nearly, by adding to the radius one. 

 8 millionth of the versed sine. 



Six balance springs weigh a grain, and are worth 2l. 5s. j 

 a grain of gold only 2d. 



Springs may be made of gold with i or i its weight of 

 copper ; they are more elastic and more brittle than hard 

 drawn steel wire, but less so than spring tempered wire. 



Hands and Bells. 



Molard's mode of moving hands at a dis- 

 tance. Mach. A. II. 159. 



Pouchy on applying small clocks to large 

 bells. A. P. 1740. 122, 



Dupont's enamelled dialplates. A. P, 1755. 

 H. 138. 



Ridrot's striking part. A. P. 1758. H. 103. 



Courtois's changeable chimes. A. P. 1769. 

 H. 129. 



Compensations and Corrections. 



Picard on clocks gaining in summer. A. P, 



L 73. 

 Lahire on the inequalities of clocks. A. P. 



1703. 285. H. 130. 



Derham on pendulums in a vacuum. Ph. tr. 



1704. XXIV. 1785. 



A half second pendulum lost a" in an hour, when placed 

 in a vacuum • when the arc of vibration was increased to 

 the same extent in the open air, it lost 6" in an hour. 



Williamson's general correction. Ph. tr. 17 19. 

 XXX. 1080, 



An equated clock, including a correction for temperature. 



