on the rate of chronometers. 381 
ponding in density to the mean state of the atmosphere, at 
some remarkable places, situated at considerable elevations 
above the level of the sea. 
.For this purpose several chronometers were supposed to 
be carefully transported from London to Geneva, every cir- 
cumstance relating to temperature and magnetism remain- 
ing constant ; and from the succeeding table it will appear, 
that an alteration in the rate of the time keeper will be 
the necessary result. In this experiment two box chrono- 
meters, and three of the pbcket kind, had their rates carefully 
determined for five days, under a mean atmospheric pressure 
of 29.86 inches, and an average temperature of 50° ; and for 
a like number of days in air corresponding in density to 28.6 
inches, being the mean atmospheric pressure at Geneva, the 
average temperature being 48°. The following alterations of 
rate resulted ; and which clearly demonstrated that a con- 
stant difference of 1,26 inches in the mercurial columns, was 
capable of affecting very sensibly the rates of the chrono- 
meters employed. 
Experiment for Geneva, elevated 201 fathoms above the level of the Sea. 
Place, 
Mean Tem- 
perature 
during the 
Experiment. 
Mean 
Pressure. 
Number of 
days. 
Mean daily 
rate of A. 
Mean daily 
rate of C. 
Mean daily 
rate of F. 
Mean daily 
rate of G. 
Mean daily 
rate of H. 
London, 
O ! 
5 ° 
Detached 
29.86 in. 
5 
U 
— 3-3 
" - 
+ 0.6 
// 
+ 2.0 
// 
— 7.1 
// 
+ 7-9 
Geneva, 
48 
28.60 in. 
S 
— 2.7 
+ 1.2 
+ ° S 
— 3.1 
+ 9*7 
Of the above alterations of rate it will be perceived, that the 
box chronometer F lost by being submitted to a diminished 
pressure ; but that the others gained. 
