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IV. On the Irregularity tit the Rate of Going of Time -piece* 

 decaf oned by the Influence of Mag net if n. An original Com- 

 municationy by Mr. I ARLEV. 



JLJlAVING ftudied the theory of clock arid watch-making 

 man)- years, as well as been, part of that time, concerned 

 in an extenfive manufactory of watches, I have had many 

 opportunities of obferving a circumttance which has far- 

 prifed every one in the trade as well as myfelf ; that watches 

 of confiderable price, and from the hands of excellent work- 

 men, often perform no better than a plain one of inferior 

 workmanihip and much lower price. Being anxious, as may 

 naturally be fuppofed, to furnifh my friends with watches or 

 clocks which would go well, I made it my bufmefs to pay 

 particular attention to whatever could contribute to their 

 perfection. With this view, I madealmoft numberlefs ex- 

 periments and observations on the various efcapements now 

 in ufe, the different con ft met ions of balances, pendulums, 

 pendulum fprings and compenfations, both for clocks and 

 watches, which have been applied by very ingenious me- 

 chanics and excellent workmen to correct the errors in the 

 rate of going, efpecially of watches, occafioned by the va- 

 rious degrees of heat and cold, change of pofition, external 

 agitation, influence of oil, friction, \anaiion of maintaining 

 power, and other caufes. 



Some of thefe contrivances are extremely well adapted to 

 aniwer the intended purpoiej but, notwithstanding all their 

 advantages, the maker and purchafer are frequently difap- 

 pointed in the performance of the machine to which they 

 are applied. Many inftarices might be produced where the 

 bed workmen have been employed, no expence fpared by 

 the maker, and the above-mentioned improvements applied 

 with the utmoft care and attention ; and yet the rate of 

 going of the watch has been more irregular than in fome 

 ordinary watches. When fuch a circumftance occurs, it is 

 extremely unplcafant : the purchafer not understanding the 



difficulties 



