Notices reJpeSiwg New Booh. 3^9 



fpme time erred 34 minutes ^6 feconds. The author gives 

 an account alio of Rivaz's experiments. The time-keepers 

 of Arnold, Rendal, and Mudge, were found to he exceed- 

 ingly correal. Mudge conliruded only three; the firft of 

 which was tried, in the year 1774, by Dr. Mafkelyne, 

 Hornfbvj Count Bruhl, Von Zach, and Campbel. The 

 other two were tried by Dr. Mafkelyne in 1777. One of 

 them, in the conrfe of 93 days, was found to have exceeded 

 tbe mean time bv only i minute i-8 fecond. It fhowcd the 

 longitude between London and Oxford within i-6 feconu. 

 The balance vibrated altogether independent of the wheel- 

 work, and always received from the moving power a new 

 impuhc, which at each vibration was uniform. The balance 

 had two fjiiral fprings, which prodjaced a very uniform adion. 

 Befides this, the machine was furniflied with a compenfation 

 balance. In imitation of the nautical time-keepers, pocket 

 chronometers were conflrufted. Thcfe ferve for determining 

 the geographical longitude at land. In thefe the free fcape- 

 ment of Mudge is employed. Emery, an artifi from Neuf- 

 chatel, made the firll:, which, after a pafljge of four weeks, 

 gave ihe longitude of St. John's, Newfoundland, eorre6t 

 within fix feconds. Another, con(lru6led by Mudfre, in a 

 voyage of 14 weeks, erred only 17 feconds. Mudlre never 

 made but two pocket chronometers. Arnold made above 

 900, of various conftruftions. His chronometers of the beft 

 kind, with gold cafes, cofl 120 guineas, with filver cafes, 100. 



In the year 1500 the art of clock- and watch- making in 

 Germany became a particular branch of bufinefs. The author 

 here gives an hiflorical fketch of the origin and prosxrcfs of 

 watch-making in Swillcrland from tlie year 1679 *" ^be pre- 

 fent tim/?, particularly in Neufchatcl and Valengin, which 

 will be read with great intcrefi. In both thefe diitrifts there 

 are at prefent 3634 clock- and watch-makers. One Abra- 

 ham Robert invented there an infirument which ferves for 

 adjulting the teeth of the wheels and pinions. 'I'he fame 

 artilt conc<iv(d the idea alfo of a dead fcapement. I'errelet 

 invented tlie inftrument for placing wheels (traiaht; and [Re- 

 corder watches, which wiml thcnifolves up. The niofl ce- 

 lebrated watchmaker in Chaux de I'ond, where there are 

 above 400, is James Droz, who has obtained great celebrity 

 by the conftruction of fome very curious automata. 



XI. Mnchini:s mvoed hy clock luurk. — Under this head (he 

 author dcfcribes, with great minutencfs, all ihofe works moved 

 by cl')ck-w()rk which are not emnloved for nuaCiMinti inne. 

 The read«'r will here fee, with piealnre, how muchean be 

 |nodutcd by luuuaa ingeriuity ; but it is not pollibic to give 

 ^4 a proper 



