404 
Mr. Harvey on the effects of density of air 
As a striking example of the power possessed by a chro- 
nometer, of immediately altering its rate to a quantity cor- 
responding with every new circumstance in which it was 
placed, and also of regaining its original rate, after it was 
again restored to its primitive condition, the following table 
may be referred to ; and in which it will be perceived, that 
the original rate with which the chronometer departed, was 
still possessed within the small quantity o."q, after the last 
experiments. During the course of observations, the time- 
keeper was subjected to pressures from 60 inches to 3 inches; 
and it will also be perceived, that the greatest deviation of 
the detached rate from the original rate, amounted only to 
o". 8 . The observations embraced a period of four months, 
and during which the temperature varied from 39 ° to 6 o°. 
Detached + 7-9 
Detached + 
// 
7.2 
28.6 in. 4" 9.7 
34 in. + 
5-3 
Detached -f* 8 -° 
Detached -f* 
7.0 
21 in. + 
38 in. -j- 
2.3 
Detached -j- 7-9 
Detached -j- 
8.0 
15 in. + 17.0 
5 in. + 26.6 
Detached -j- 8 - 2 
Detached -f 
7-5 
12 in. + 1 9-o 
5 in. 4 - 26.9 
Detached -j- 7 - 8 
Detached -f- 
7-9 
60 in. — 6.6 
40 in. — 
3-0 
Detached -j" 8 -7 
Detached + 
7-7 
3 in. + 28.0 
The occasional imperfections of the valves of the conden- 
sing machine and of the air pump, have likewise afforded 
some interesting proofs of the truth of this investigation. 
