396 Mr. Harvey on the effects of the density of air 
the same chronometer for Geneva, Madrid, Chimborazo, &c. 
The time-keeper R likewise lost with a diminution of pres- 
sure. The chronometers A and C received increments to 
their rates, in perfect conformity to those obtained in former 
experiments. 
Changes produced in the rates of the chronometers A, C, F, R, in con- J 
sequence of small but irregular decrements in the pressure. 
Mean 
Temp. 
Mean 
Pressure. 
No. of 
days. 
Mean 
rate of A 
Mean 
rate of C. 
Mean 
rate of F. 
Mean 
rate of R. 
Diff. of 
pressure. 
Change of 
rate in A. 
Change of 
rate in C. 
Change of 
rate in F. 
Change of 
rate in R. 
O 
47 
49 
Inches. 
29.26 
28.30 
4 
4 
// 
— 2.9 
— *s 
II 
+ 3-4 
+ 3-9 
1/ 
+ 2.5 
+ i -3 
— 6.5 
— 7-3 
Inches. 
— O.96 
1/ 
+ >1.4 
— 3 2 
*4“ 0.6 
// 
+ 0.5 
— 1.8 
+ 0.8 
/I 
— 1.2 
+ °-3 
— 1.2 
+ 0.8 
— 1-7 
— 0.8 
+ 0.9 
— 1. 1 
50 
48 
29.68 
28.00 
4 
4 
—4.7 
— 4.1 
+ s.i 
+ 2.9 
+ 1.6 
+ 0.4 
— 6.4 
— 7-5 
*T 
_ 1.68 
+ 1-69 
— 0.69 
46 
4 2 
29.69 
29.00 
4 
4 
— 
— 
4- 1.2 
— 0.5 
— 
To throw as much light as possible on this very interesting 
and important part of the investigation, six distinct sets of 
experiments were performed with the pocket chronometer 
H, and which, as before remarked, has been found uniformly 
to maintain an excellent rate when under a constant atmos- 
pheric pressure; and to display an immediate alteration 
whenever the density of the air was sensibly changed. In 
the succeeding table, it will be observed by inspecting the 
fifth and sixth columns, that in every case the rate of the 
time-keeper was increased as the density was dminished, and 
vice versa; and also, that an alteration of 0.6 inches in the 
mercurial column produced a sensible alteration in the time- 
keeper. The want of perfect proportionality in the rates, 
