394 Mr. Harvey on the effects oj the density of air 
alterations of rate occasioned by small depressions of the 
mercurial column below the average state of the barometer 
for some days previous to each experiment. 
i 
Changes produced in the rates of the Chronometers H, O, P, Q, in conse- 
quence of a diminution of pressure denoted by one inch of mercury. 
Mean 
Temp. 
Mean 
Pressure. 
Mean daily- 
rate of H. 
Mean 
Temp. 
Mean 
Pressure. 
Mean daily 
rate of O. 
Mean 
Temp. 
Mean 
Pressure. 
Mean daily- 
rate of P. 
Mean 
Temp. 
Mean 
Pressure. 
Mean daily 
rate of Q. 
O 
47 
3°-3 
// 
+ 8.5 
O 
47 
30.I 
„ 
•f* 8.0 
0 
45 
30.I 
// 
7 -° 
O 
49 
29.9 
a 
4 - 4 - 2 
46 
29.3 
+ 9-3 
48 
29.I 
+8 , 
46 
29. 1 
— 7-9 
50 
28.9 
4 3-4 
The chronometer H was employed in many of the former 
experiments, and it will be perceived that it constantly gained 
with less pressure. In the investigations instituted for Ge- 
neva and Madrid, for example, the increments communicated 
to its rate were respectively T.8, and £".2 ; and in the pre- 
sent instance an abberration of the same kind was produced, 
amounting to o".8 ; the increment being smaller than either 
of the preceding, in consequence of a less diminution of pres- 
sure. The close approach to numerical equality also in the 
changes of rates recorded in the preceding table, is not un- 
worthy of notice, the differences being respectively — o".8, 
-j- o." 7 , — o." 9 , and -f- o"8. The time devoted to each set 
of experiments was three days. 
In another set of experiments, the pocket chronometer D, 
and the box chronometer F, were again resorted to, and 
placed under the different pressures recorded in the succeed- 
ing table. The mean temperatures during the several 
periods of observation underwent no very considerable 
