300 Chronometers. 



In our researches on this subject, we have found that the defect 

 in the correction for change of temperature, is amongst the least of 

 the difficulties to be contended with ; and the value of the princi- 

 ple of adjustment which we have discovered has been eminently 

 proved by the accurate performance of our chronometers, which 

 have been exposed to the severities of the arctic winters, in all the 

 Polar voyages. In one of those voyages, eleven out oi fifteen chro- 

 nometers stopped from the cold ; whilst four made by us, (all of 

 ours that were sent) maintained the same rates at Melville island 

 that they were found to have in London after the return of the ex- 

 pedition. 



The chronometrical parts of our chronometers consisting of the 

 compensation balance and the detached escapement, are the same as 

 invented before 1766, by the eminently distinguished artist, M. 

 Le Roy, of Paris, with the important improvement of the detant on 

 a spring instead of on pivots, as made by the late Mr. Earnshaw ; 

 together with some minor but useful alterations of our own, in the 

 execution and arrangement suggested by experience. 



We have already said that chronometers made by the same artist, 

 do not always perform equally well, although the same workmen are 

 employed, the same labor is bestowed, and the same attention paid 

 to each. Some modern artists have endeavored to remedy this de- 

 fect by means of mechanical contrivances, some of which are of con- 

 siderable ingenuity and apparent plausibility ; but, however beauti- 

 ful these contrivances are in theory, they have produced no practi- 

 cal advantage, no one has yet discovered the seat of the disease, or 

 the cause of so remarkable an effect. We reassert that no mechan- 

 ical contrivances can remedy the defect : it is to be attained only by 

 a knowledge of the principle which we have discovered. 



Le Roy's original inventions of the balance, for compensating for 

 the changes of temperature, and the escapement, were entitled, from 

 their beautiful simplicity, to the reward so justly bestowed upon him, 

 and with the improvements above alluded to, by our countryman 

 Earnshaw, continue unrivalled : in fact they are generally adopted 

 by all intelligent chronometer makers. 



We consider that the best balance is that composed of laminae of 

 brass and steel, when properly proportioned, and worked so that the 

 particles are placed under no particular or partial constraint, which 

 might prevent their free and natural action throughout the whole 

 periphery of the balance. This we consider an important requisite ; 



