for determining the difference of meridians , &c. 115 
A — B — /3 ( A — ■ E ) = A, — B, — (1 (A, — E) 
whence we find 
— 0 
(A/ — B,) — (A — B) 
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 h -f- A # and 24 h + B, for A, and B, if 
the interval be one day ; 48 h -f- A, and 48 h B y if two days, 
and so on, so that ( n being the number of days elapsed) 
we get 
_ (A, — B,) — (A — B) 
n x Z4 h 4 A y — A 
In like manner may the rate 7 of the chronometer at C be 
found by comparison with the clock at Z thus, 
(Z/'— C") — (Z*— c") 
n x 24 h + Z," — Z" ' 
If there be intermediate chronometers, the rate of each 011 
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 y — B y = 7 h 50 ra 7‘-90 A / = i8 h 19“ 4 i s, 83 
18th. A — B = 7 46 8 -28 A = 18 32 21 -88 
(A, — B y ) — (A — B)= + 3 59 ‘62 A,— A= — o i2 ra 40 s -05 
— g = ; 4 »Jo~ ”^-o S 1- -74 ; ^ = -4”l-74-^24 l 
Whence the rate on mean time =-— 5 S, 83. 
