37 6 Mr. Harvey on the effects of the density of air 
recorded in the first horizontal line of the succeeding table. 
The time-keepers were placed at the same instant beneath 
the receiver, and the air exhausted until the mercurial 
column sunk to half an inch ; when the singularly large 
increments entered in the second line were produced. In 
the third horizontal line of the table, the rates of the chrono- 
meters are given after they were restored to the full pressure 
of the atmosphere ; and it is remarkable, how closely they 
approximate to the primitive rates, the greatest aberration 
being only i".3, in chronometer C. Nor ought the close 
approximation also of the large increments produced by the 
exhaustion to a state of equality to be entirely overlooked. 
The chronometers were taken each day from beneath the 
receiver for the purpose of comparison, and being wound 
up ; a circumstance only necessary once a week, with the 
chronometer A. 
Experiments with Pocket Chronometers, B, C, D. 
Mean 
Temp. 
Pressure. 
Number 
of Days. 
Mean daily 
rate of B. 
Mean daily 
rate of C. 
Mean daily 
rate of D. 
58° 
detached 
30.04 in. 
6 
+ 4 ". 7 
+ o".3 
+ 3".6 
5 8° 
•§ inch 
6 
+ 2 3". 5 
+ i8".6 
+ 23".5 
56 ° 
i 
detached 
30.01 in. 
6 
+ 5". O 
+ i".6 
+ 2". 4 
The preceding changes having been produced by dimi- 
nishing the density of the air in the ratio of 60 to 1 ; an 
