ON SOME POINTS IN THE METEOROLOGY OF BOMBAY. 77 
The double progression is exhibited both in the clouded and in the clear 
seasons, with a slight difference only in the hours of maxima; the principal 
maximum in the cloudy season being at 205 instead of 29%, and the inferior 
maximum in the clear season being at 12" instead of 10%. 
diurnal variation, like that of the temperature, is more than twice as great in 
the clear as in the clouded season, marking distinctly the connexion subsist- 
ing between the phenomena of the temperature and of the gaseous pressure. 
TABLE II. 
The range of the 
Bombay, 1843.—Comparison of the Temperature and of the Gaseous Pres- 
sure in the months of May, June, July and August, when the sky is usually 
covered with clouds; and in November, December, January and February, 
when the sky is usually clear. 
Hours PE Mean Time at __-‘Temperaturen 
ombay. 
Astronomical Reckoning. Peers Eg eae bay te oly 
18 741 81-9 
20 75°3 83:1 
22 781 84:3 
0 80°8 85°1 
2 81:9 85°6 
4 81:7 85°4 
6 79°6 84:3 
8 78-4 83-4 
10 76:9 83:0 
12 76-2 82:7 
14 75°7 82-6 
16 74:9 82:2 
Means .......0. 2.5 778 83°7 
Gaseous Pressure. 
\November, December, |May, June, July 
January and February.| and August. 
in. 
29-344 
29-368 
29°391 
29-353 
29-230 
29-195 
29-199 
29-248 
29308 
29°316 
29-295 
29-285 
29-298 
in. 
28-782 
28-806 
28-798 
28°782 
28-746 
28-724 
28-740 
28-754 
28-800 
28-775 
28-754 
28°753 
28°763 
If we now turn our attention to the phenomena of the direction and force 
of the wind, we find by Dr. Buist’s report, that for 200 days in the year there 
is a regular alternation of land and sea breezes. 
usually about 104, or between 10” and 14", blows strongest and freshest towards 
daybreak, and gradually declines until about 994, at which time the direction 
of the aérial currents changes, and there is generally a lull of an hour or an 
The sea breeze then sets in, the ripple on the 
surface of the water indicating its commencement being first observed close 
hour and a half’s duration. 
in shore, and extending itself gradually out to sea. 
The land breeze springs up 
The sea breeze is freshest 
from 2" to 44, and progressively declines in the evening hours. 
The diurnal variation in the force of the wind during these 200 days is 
therefore obviously a double progression, having two maxima and two mi- 
nima; one maximum at or near the hottest, and the other at or near the cold- 
est hour of the day,—being the hours when the difference of temperature is 
greatest between the columns of air which rest respectively on the surfaces 
of land and sea; and two minima coinciding with the hours, when the surface 
temperature over the land and over the sea approaches nearly to an equality. 
In the remaining portion of the year the diurnal range of the temperature 
is most frequently insufficient to produce that alternation in the direction of 
the wind, which prevails uninterruptedly during the larger portion. There 
appears however to have been only one month, viz. July, in the year 1843, in 
which there were not some days in which the alternation of land and sea 
breezes was perceptible. The causes which produce the alternation are not 
