OBSERVATIONS IN FOUR BALLOON ASCENTS. 
321 
reeled for temperature, and the temperature of the air, at the lower and upper 
stations respectively ; L, the latitude. The temperature of the air for the position of 
the balloon has been derived from the readings of the aspirated dry thermometer 
(column 5), except on August 17, when the free thermometer only was observed. The 
temperature and barometric height at the earth’s surface have been taken by inter- 
polation from the comparative observations at different stations ; the mean height 
above the sea, of the stations referred to, having been included. The numbers, it will 
be seen, have been given only to the nearest 10 feet. 
Many observers in different parts of the country made corresponding meteoro- 
logical observations, generally at hourly intervals, on the days of the several ascents. 
These have been arranged in compact tabular order by Colonel Sykes, Chairman 
of the Kew Committee, and are appended to this report. The stations selected for 
comparison with the different days’ observations have been those which lay nearest 
to the course of the balloon. The temperature of the air at the surface of the earth, 
has been derived from the mean of the observations at all the selected stations, both 
as regards its absolute value and hourly change. The hourly change of the barometer 
has been taken from the observations at all the selected stations ; but its absolute 
height has always been derived from the mean of the observations at the Royal 
Observatory, Greenwich, and at the residence of Jambs Glaisher, Esq., Lewisham. 
The error likely to result from adopting the height at these two stations as the 
standard of reference will be in any case very small, and can only affect the absolute 
and not the relative heights of the balloon by a few feet ; while any uncertainty with 
regard to the index errors of other barometers is obviated. The quantity -h 0*028 
has been added to the readings of the terrestrial barometers, on account of the index 
errors of the balloon barometers. 
The following are the stations whose observations have been employed, and the 
resulting mean values for each day of ascent. 
August \7, 5 stations, viz. — Greenwich; Lewisham; Enfield; St.John’s Wood; 
Cambridge. 
Mean temperature of the air at 4'’ p.m. = 71°*2 ; hourly change = — 1°*1. 
Mean height of the barometer at 4^^ p.m. =29*740 in. ; hourly change = —0*036 in. 
August 26, 5 stations, viz. : — Greenwich ; Lewisham ; St. John’s W’ood ; Kew 
Observatory; Stone Rectory, Bucks. 
Time. 
h 
4 P.M. 
5 
6 
7 
Temperature of the Air. Barometer. 
( 
, 
r 
_A. ^ 
Mean. 
Hourly Change. 
Mean Height. 
Hourly Change. 
69*7 
67*5 
65*2 
62*7 
O 
-2*2 
— 2*3 
— 2*5 
in. 
29*949 
*959 
*964 
*985 
in. 
-l-OOlO 
4-0*005 
-1-0-021 
2 u 2 
