402 
Mr. Harvey on the effects of density of air 
chronometers produce a rate agreeing exceedingly near 
with mean time ; the entire rate for twenty-four hours being 
-f- T ; .o, agreeing very nearly with its former detached rate. 
Hence it may be inferred, that the change produced in the 
rate of a chronometer by diminishing the density of the air, 
is immediate and uniform in its effects ; and so also is the 
effect produced by increasing it. 
It may not be uninteresting to furnish a few examples 
illustrative of the power which most chronometers have of 
regaining their original rates, or very nearly so, after they 
have been subjected to pressures, both considerably above and 
below the mean density of the air ; a property by which they 
are enabled to recover any temporary derangement they 
may undergo. The following instances are selected from 
the time keepers placed under the receiver of the air pump. 
The detached rates are those obtained under the ordinary 
circumstances of the atmosphere. The pressure to which the 
chronometers were subjected, are denoted by the several 
inches of quicksilver. 
Examples of Chronometers having nearly regained their ori- 
ginal rates, after being subjected to different Pressures 
under the Receiver. 
Detached 4 4.9 
3 in. —23.8 
Detached -f 2.5 
Detached — '6.3 
5 in - + 4-3 
Detached — 5.9 
// 
Detached + 7.5 
5 in. + 26.9 
Detached -J- 8.7 
Detached -}- 4.4 
5 in. -f 21.2 
Detached -f 3.4 
Detached -j- 7.9 
12 in. -f- 19.Z 
Detached + 8.2 
Detached — 1 .9 
15 in. + 4.2 
Detached — 2.6 
Detached — ■ 5.9 
20 in. — 4.0 
Detached — 6.4 
Detached -j- 6.5 
26 in. + 9.5 
Detached -j- 7.3 
1 
