for determming the difference of meridians, &c. 117 



Rates of the Chronometers from the 21st to the 22d. 



Baker, No. 744. 

 Z,— - C, = 8^ C" 47'-04 Z^ = 1 7^ 47"° 55''-62 



Z — C = 7 56 48 '40 Z = 17 38 56 'lo 



+ S 58 -64 + o 8 59 -52 



Being a rate of — 1^*25 on mean time. 



The rates originally assigned to the chronometers on leav- 

 ing Paris and London, were respectively (on mean time), 



Motel No. S9i + i'.8. Baker 744, + i'.2o. 



The former, then, in the interval must have altered its rate 

 (if that deduced from the observations of the 18th and 19th 

 be correct), no less than — T'^S ; and between the 18th and 

 21st, must have again accelerated its daily rate by 3^-31, 

 fluctuations not to be supposed in a chronometer of any cha- 

 racter. It is therefore probable that the rate — 5''83 of the 

 i8th-i9this incorrect, and the observations being positive, 

 and liable to no errors capable of accounting for so large a 

 deviation, the cause, on this supposition, can lie nowhere but 

 in some accidental derangement in that interval. Now it 

 unfortunately happens, that the interval B — B', on the 18th, 

 to which this suspicious rate is to be applied, is no less than 

 4in> 2o'-6, which produces a correction of — o'-i7, or nearly 

 two-tenths of a second in the result of that night's obser- 

 vations. 



If we examine the individual observations of both nights, 

 on which this rate depends, we shall find no satisfaction, 

 though they tend to confirm the suspicion of a derangement 



