on the rates of chronometers. 401 
estimate the exact value of such minute inequalities. Indeed, 
the mean of the hourly observations from noon to midnight 
presented the same result as the mean from midnight to 
noon, the former being -|- i".i2, and the latter i".io. 
The entire rate for the twenty-four hours amounted to 
+ 2 6". 6, being an increase on its detached rate of 17 ". 6 . In 
like manner, the mean of three comparisons for the first of 
the horary observations with the box chronometer presented 
a rate of + 6". 7 6 ; whereas the detached rate during the 
same time would have been -f o".o8, exhibiting an increment 
of o".68 due to the diminished density of the air. By con- 
tinuing the horary observations during the twenty-four 
hours, it was found that the mean of the horary rates for the 
first twelve hours was + o" .92, and of the last -f- o".72. The 
entire rate for the whole period was -|- 2o".4, being an incre- 
ment to its detached rate of 18". 5. 
The succeeding day the two chronometers were restored 
to the full pressure of the atmosphere ; and the first hour 
after their restoration, an attempt was made to discover the 
same increment in the rate of the pocket chronometer as that 
which it possessed under the receiver, but without effect ; 
the mean of four comparisons giving only a rate of -j- o".45, 
an increment bearing evidently a relation to the primitive 
detached rate of the time-keeper . At the end of three hours 
the mean rate per hour was found to be 4- o".4o ; at the end 
of six hours 4“ ; at the expiration of nine hours 
.41 ; at the end of eighteen hours 4- o".39 ; and at the 
end of twenty-four hours 4- o". 44 ; the mean of the whole 
being 4- o".42, and producing a rate for the entire twenty- 
four hours of 4- 10". 08. Similar observations with the box 
mdcccxxiv. 3 F 
