ME. H. F. BLANFOED ON THE WINDS OF NOETHEEN INDIA. 
581 
as at its minimum in October or November. At the former period it is less than at 
Dacca, at the latter nearly three times as great. At these two' stations the periods of 
maximum and minimum are approximately the same, and about a month later than at 
most stations to the westward. Calms are not very common at any time of the year, 
and occur chiefly at the close of the south-west monsoon. 
The wind-system of Akyab differs from that of Chittagong in much the same way as 
this latter diflers from that of Dacca, i. e. the corresponding phases of the wind’s rota- 
tion occur about six weeks or two months later at the more southerly station ; and 
while the average direction of the summer monsoon is less easterly, that of the winter 
monsoon is less westerly. Thus at Akyab northerly elements preponderate over southerly 
in April, and southerly over northerly in October, the reverse of the case at Chittagong ; 
in other words, both monsoons continue to be felt on the coast of Akyab one or two 
months after the change has occurred at Chittagong. This accords completely with the 
results of Captain Maury’s discussion of ship observations in the Bay of Bengal*, and 
is also what might be anticipated from the character of the barometric changes pre- 
sently to be" discussed f. The result is of high importance to the theory of the forma- 
tion of cyclonic storms, respecting which I shall say a few words in the sequel. One 
other point of interest to be noticed in the Akyab wind Table is the interruption of the 
otherwise regular retrograde movement of the winds by a sudden westing in August 
through one point of the compass, followed by a return to eastward in September. 
This reminds us of the similar phenomenon already noticed in the wind Tables of the 
North-western Provinces and Bengal. 
Summary . — From the foregoing discussion of wind-registers it appears that the wind- 
system of Northern India is very different from that of the adjacent seas. Instead of 
two monsoons from north-east and south-west prevailing alternately during about equal 
periods of the year, we find a great diversity of prevalent wind-currents, depending on 
the directions of the mountain-ranges and great valley plains ; and, with respect to 
period, to be classified under three rather than two distinct seasons — excepting, indeed, 
in Upper Assam, where the normal monsoons prevail. Thus in the cold- weather months 
(November to January) the winds are light or completely calm, and the air flows in a 
gentle current from the plains of Upper India and the Punjab down the valleys of the 
Indus and the Ganges, or across the hilly watershed of Central India to join the north- 
east or east monsoon of the peninsula proper. This appears to have a distinct source 
in the hill-region of Chota Nagpore and the country south of the Satpooras. It is 
possible that in Upper Assam and in the Upper Punjab, at the tw T o extremities of the 
Himalaya, some portion of the cool air from the transmontane region may find egress 
to the southward ; but if so, the amount must be small, and the mountain-barrier of the 
Himalaya, which throughout the interval of 1500 miles extends unbroken along the 
northern margin of our area, completely secludes India from the influence of more 
* Physical Geography of the Sea, 12th edition, p. 368. 
t See post, Part II., pp. 603, 604. 
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