for determining the difference of meridians, &c. 115 



A — B — /3(A — E)=A,— B, — ^(A, — E) 

 whence we find , , „ , , ^ „, 



^ (A, — B,) — (A — B) 

 H — A, — A 



In this formula it is to be observed that A, and B^ are each 

 greater than 24 hours ; but as timekeepers only register 

 excesses above 12 hours and its multiples, if we wish' to 

 denote by A^ and B^ the mere readings off of the time- 

 keepers, we must put 24*^ + A^ and 24^ + B, for A^ and B^ if 

 the interval be one day ; 48^ + A, and 48^ + B, if two days, 

 and so on, so that (n being the number of days elapsed) 



^^ ^^* — 5 = (A.-B,)-(A-B) 



f^ n X 24*+ A^ — A 



In like manner may the rate <y of the chronometer at C be 

 found by comparison with the clock at Z thus, 



_ (z;--c;o-(Z"-C) 



^ nx2^^+ Z,"— Z" • 



If there be intermediate chronometers, the rate of each on 

 that immediately preceding or following it may be found in 

 exactly the same way. 



Computation of the Rates of the Chronometers. 



From the 18th to the 19th. 



1. Lignieres Chronometer, or that at station B. Motel, No. 39. 



19th. A^ — B^ = 7^ 50™ 7*-9o A, = i8M9'°4i'-83 



18th. A — B = 7 46 8 -28 A = 18 32 21 -88 



(A^— B,)--(A--B)= + 3 59 -62 A,-A=— o 12™40«05 



— ^= z^^Jo^\^z^lo^'os =4"i--74; /3 = — 4™l'-74-T-24'' 

 Whence the rate on mean time = — 5'-8s. 



