322 
MR. J. WELSH’S ACCOUNT OF METEOROLOGICAL 
October 21, 2 stations, viz.—Greenwich and Lewisham. 
Temperature of the Air. 
Barometer. 
Time. 
f 
Mean. 
.A , 
Half-hourly Change. 
c 
Mean Height. 
— ^ 
Half-hourly Change. 
h m 
2 30 p.M. 
5°87 
P 
0-0 
in. 
29-900 
in. 
- 0-001 
3 0 
587 
— 1-0 
•899 
- -004 
3 30 
577 
- 0-8 
•895 
- -007 
4 0 
56-9 
- 0-8 
•888 
•000 
4 30 
56 T 
•888 
November 10, 2 stations, — Greenwich and Lewisham. 
Temperature of the Air. 
Barometer. 
( 
( 
Half-hourly Change. 
Time. 
Greenwich. 
Lewisham. 
Mean. 
Mean Height. 
h m 
O 
O 
0 
in. 
in. 
2 30 P.M. 
48-6 
50-7 
49-7 
29-978 
-0-003 
3 0 
48-0 
49-3 
48-7 
•975 
- -004 
3 30 
49-0 
49-6 
49-3 
•971 
Mean 

49-2 
As the progress of the temperature at these two 
stations has been very irregular 
and indefinite. 
a mean 
result has been adopted, and 
no allowance 
made for hourly 
change. 
The height, above the mean sea level, of Greenwich =159 feet. 
The height, above the mean sea level, of Lewisham = 80 feet. 
Mean of both stations =120 feet. 
Columns 5-10 contain the results of observations with the aspirated dry and wet 
thermometers; the tension of vapour, relative humidity (100 being complete satura- 
tion), and the calculated temperature of the dew-point having been deduced by 
Dr. Apjohn’s formula and Dalton’s Tables of the elasticity of vapour. Column 1 1 
contains the readings of the dry thermometer, corrected for hourly change by means 
of the numbers deduced above from observations at different stations. The numbers 
in this column have been employed in the subsequent discussions and in the pro- 
jected results. 
Columns 12-17 contain the observations of the free dry and wet thermometers 
similarly reduced. Columns 18 and 19 contain the results of the direct dew-point 
observations with Regnault’s Hygrometer, and the corresponding tension of vapour 
derived from Dalton’s Table. When numbers are entered in column 18 with the 
sign — after them, it is meant that the temperature in the hygrometer had been 
lowered to the degree stated, but that no dew was deposited. 
All the readings of both pairs of dry and wet thermometers have been corrected 
for index error ; the corrections to the dew-point thermometer were very small, and 
have been neglected. 
