395 
on the rates of chronometers . 
change ; and from the uniformly decreasing nature of the 
rates it is fair to infer, that the alterations resulted from 
diminished pressure alone, and that the successive inches of 
quicksilver were capable of producing them. It is worthy 
of observation also, that the same pressure which produced 
an increment in the rate of the former chronometer, occa- 
sioned a decrement in that of the latter ; and by a reference 
to several of the foregoing experiments, it will be found 
that the time-keeper D in all cases gained with less pressure, 
and the chronometer F the contrary. 
Changes produced in the rates of the Chronometers D, F, in 
consequence of regular decrements in the pressure 
denoted by an inch of mercury. 
Mean 
Temp. 
Mean 
Pressure. 
No. of 
Days. 
Mean daily 
rate of D. 
Mean 
Temp. 
Mean 
Pressure. 
No. of 
Days. 
Mean daily 
rate of F. 
0 
51 
30.4 
5 
+ 4.2 
O 
51 
30.4 
5 
4 ” 3-9 
50 
29.4 
4 
4 " ®*4 
50 
29.4 
4 
+ 3.1 
50 
28.4 
4 
+ 7-4 
50 
28.4 
4 
4 s 2.5 
48 
27-4 
4 
4 ° 8.0 
48 
27.4 
4 
4-2.1 
In the next set of experiments, the time-keepers A, C, F, 
and R were employed. The results are recorded in the next 
table ; and it will be perceived that a difference of pressure 
amounting only to 0.69 inches of mercury, for twenty-four 
hours, was capable of producing an alteration in the rate of 
F, of the same kind as observed in the experiments with 
