622 
ME. H. F. STANFORD ON THE WINDS OF NORTHERN INDTA. 
the winds on peaks and ridges are always much influenced by the direction of the 
valleys. I am not prepared to deny the possibility of a return current being occasion- 
ally felt at 8600 feet (the height of Dodabetta) ; but the evidence is at least inconclusive, 
and the superior velocity and steadiness of the south-west monsoon render it probable 
that it is a current of greater depth and volume than the north-east monsoon. As to 
the north-west monsoon of Australia, and the evidence of the Merapi volcano, I do not 
think the case has much bearing on the question of the monsoons of India. It is clear 
that the monsoon is not a single great current, proceeding to or from Central Asia, but 
consists of several currents, to some extent independent of each other, flowing to or from 
more than one centre on the Asiatic continent ; and there may be a deep north-easterly 
current flowing from India to the south and south-west of that region, and a very shallow 
one opposite the Malay peninsula. I certainly could not accept, without much stronger 
evidence than has yet been adduced, the complicated system of winds during the south- 
west monsoon, supposed by Dr. Muhry, viz. a south-west current up to about 9000 or 
10,000 feet, which is a retroversion of the lowest stratum of the trade-wind; above this 
“ the remainder of the trade-wind, moving undisturbed from the north-east ; and over 
this the returning anti-trade moving from south-west at a still greater elevation.” With 
much of what Dr. Muhry has written on the subject I should, however, add that I 
cordially agree. 
The annual range of atmospheric pressure, which at Roorkee, when reduced to sea- 
level, amounts to 0-6 inch on the means of the months, is due principally to a change 
of density in the lower 7000 or 8000 feet. The proportion below Simla and Darjeeling 
is nearly seven tenths of the whole. Six sevenths of this in the case of the latter are 
probably due to the expansion of the atmosphere by increase of temperature, and only 
one seventh to the substitution of water-vapour for dry air. But water-vapour, though 
of subordinate importance in this respect, plays an important part in communicating 
heat to the higher strata of the atmosphere, carrying it upwards by its diffusion in the 
form of latent heat which is emitted by its condensation, and also by arresting and 
absorbing the solar and terrestrial radiation. The temperature-difference of Daijeeling 
and Goalpara varies nearly inversely as the humidity of the lower station. 
To conclude : I have in this paper sketched out the general system of normal wind- 
currents of Northern India, and have shown in general terms their relations to heat and 
moisture, as far as they are to be gathered from existing observations. This work is 
almost an essential preliminary to any more detailed inquiry ; but it is to be regarded 
as only a first rough sketch of a very important and characteristic wind-system. In 
many, I may say in all , respects it requires detailed verification. In the first place, the 
relations of the winds to temperature, moisture, and pressure have to be verified by the 
reduction of the original data in the form of wind-roses of these several elements ; the 
progressive diffusion of heat and vapour vertically in the hot weather has to be followed 
out in detail, if possible, at a well-selected series of stations at heights intermediate 
between the present observatories and the plains ; and the physical analysis which I have 
