CATALOGUE. PHILOSOPHT AXD ARTS, PRACTICAL MECHANICS. 195 



Criaham's correction for temperature. Ph. tr. 

 1726. XXXIV. 40. 



Mercury in a tube of glass or of varnished brass. 



Tliiout's new corrections for timekeepers. A. 



P. 1737. H. 107. 

 Cassini's compensation pendulum. A. P. 174 1 • 



363. H. 147. 

 Eiiicott's two compensations. Ph. tr. 1751. 



479. 



One of them is eSected within the weight of the pendu- 

 lum. 

 Short's history of compensation pieces. Ph. 



tr. 1751. 517. 

 Guinette's compensation. A. P. 17G0. H. 155. 

 Lemonnier on the increase of length of two 



rods. A. P. 1761. 11.26. 

 Leroy's compensation. A. P. 1769. H. 131. 

 Lambert on the resistance of the air to pen- 

 dulums. Bcrl. Ephem. 1/76. 

 Bernoulli on compensations. A. Petr. I, ii. 



109. 

 Grenier's pendulum. Roz. XXIX. 1 14. 

 Crossthwaite. Ir. tr. 1788. II. 7. Kepert. III. 



254. 

 Fordyce on a new penrlulum. Ph. tr. 1794. 2. 



The fixed cheeks which embrace the spring are raised by 

 a bar of the same materials as the pendulum ; but aE much 

 longer as to compensate for the expansion of the fixed sub- 

 stance. 



Pine's new pendulum. Repert. III. 15. 



The method resembles Fordyce's ; but the expanding bar 

 is made too short. 



Riltenhouse. Am. tr. IV. 26. Nich. III. 522. 

 ' Repert. XiV. 323. Ph. M. IX. 298. 

 On compensations for temperature. Nich. I. 



66, 575. III. 205. 

 Varley on the errois arising from magnetism. 

 Ph. M. I. 16. 



A difference of 1 2' in 24 h. was observed in the different 

 positions of a watch. 



Diihler's compensation for clocks. Gilb. VII. 



318. 

 Two rods which carry a cross bar support- 



ing a bob or weight. Cavallo, N. Ph. III. 

 PI. 18. f. 10. 

 Ben zenberg's gridiron pendulum. Gilb. XIV, 

 ,315. Nich. VII. .300. 



The balances of brass and ste^l, carrying a weight at the 

 ciid, are best made by immersing the steel into melted brass, 

 and turning it afterwards into a proper form. 



Sometimes the compensation is made by the flexure of a 

 compound bar, which only widens or contracts the distance 

 of the two pins between which the spring plays. 



Earnshaw professes to make the vibrations of the balance 

 in short arcs more rapid than in larger, in order that the 

 contraction of the arc by the increased tenacity of the oil 

 may compensate for the unavoidable diminution of force of 

 the balance spring, which is relaxed by continual action. 



Sympathy of Clocks. 



Hague on tiie invariable agreement of twy 



clocks. Coll. Acad. I. 252. 

 Ellicot on the mutual influence of two clocks. 



Ph. tr. 1739. 126. 



The clocks resting against the same rail agreed for scveraF 

 days, without varying a second : when separate, they varied 

 l'36" in 24 h. The slower, having a longer pendulum, set 

 the other in motion, by the intervention of the rail, in I6i', 

 and stopped itself in 36j' : when the cases were connected 

 by a bar of wood, the shorter pendulum was set in motion 

 in 6', and the longer stopped in 6' more. On a stone floor 

 the effects were slower. The shorter pendulum could not 

 put the longer one in motion, because, as its vibrations be- 

 came wider, they were still slower. 



Supports for Clocks, and Manage- 

 ment of Timekeepers. 



Instructions for the u.se of pendulum watches 



at sea. Ph. tr. 1669. IV. 937. 

 Massy on using clocks at sea. A. P. Prix, 



I. ii. 

 Biesta's suspension for a clock. A. P. 1770. 



H. 114. 



Arsandaux's suspension was judged injurious. A. P. 



Cumming recommends that a watch or clock be fixed to 

 a block of marble. 



Berthoud found that a clock lost 297" in a day, by being 

 more firmly fixed ; and Bernoulli, in the memoirs of the 



