624 
MR. H. F. BLANFORD ON THE WINDS OF NORTHERN INDIA. 
normal state of the winds and atmospheric pressure at these two periods of the year, 
and how far they help to throw light on the conditions which favour the formation of 
these storms. 
It has been shown, in the summary of Part I. of the foregoing discussion, that southerly 
winds set in on the coast of Bengal in February, at first as mere local sea-breezes, and 
that as the sun ascends in declination they come from further out at sea and extend 
further inland. The change from north to south takes place on the Indian coast earlier 
than on that of Arakan ; but in May southerly winds prevail over the whole of the 
Bay*, and indeed, according to Maury and Cornelissen, down to the line. But gene- 
rally the winds are light except near the coast, and the south-west monsoon has not yet 
set in. The mean pressure at Port Blair, reduced to sea-level, is 29*788 inches; at 
Akyab 29*774; at Madras 29*747 ; at Calcutta 29*685; so that the mean barometric 
gradient is about 0*1 inch in 800 miles, or half as great as in July. There can then be 
no question of conflicting currents being the cause of cyclones in this month, unless it 
be assumed that (as Sir John Herschel has suggested in the case of the West-Indian 
storms) an upper return current strikes down with a high velocity into the southerly 
surface current. But there is no evidence of this in any case that I have investigated ; 
and were this the determining cause, it would remain unexplained why cyclones are not 
more frequent during the south-west monsoon, when the lower current evidently at sea’, 
and the upper therefore inferentially, have a higher velocity than in May. It would 
still remain to ascertain what brings the upper current down. 
In October the circumstances are very different. Unsteady north-east winds do then 
blow on the coast of Orissa, while south-west or more frequently south-east winds prevail 
* The Port Blair observations of four years give the following result 
, in May 
North. North-east. East. 
South-east, 
South. South-west. 
West. North-west. 
8 
13 
4 
26 
27 
146 
7 
17 
The following Table 
is taken from a 
notice of Cornelissen’s work, 
“ Route • 
voor Stoomschepen &c.,” i 
Zeitschrift d. osterr. met. Gesellschaft ; 
I have not seen 
the original work : — 
Winds in 
the Indian Ocean, north of 1C 
*° south latitude, in the month of May. 
80° to 90° East Longitude. 
15°-20° N. 
10°-15° N. 
5°-10° N. 
0-5° N. 
0-5° S. 
6-10° S. 
North-east . 
. . 5 
7 
4 
3 
12 
10 
East-south 
. . 20 
20 
14 
16 
33 
72 - 
South-west . 
. . 68 
59 
64 
49 
26 
8 
West-north . 
. . 5 
9 
16 
25 
16 
5 
Calms . . . 
. . 1 
5 
2 
7 
13 
5 
90° to 100° East Longitude. 
North-east . 
. . 1 
7 
4 
5 
19 
10 
East-south 
. . 10 
6 
12 
18 
29 
68 
South-west . 
. . 65 
63 
67 
51 
21 
10 
West-north . 
. . 17 
16 
11 
20 
16 
7 
Calms . . . 
. . 7 
8 
6 
6 
15 
5 
