614 
ME. H. E. BLANEOED ON THE WINDS OF NOETHEEN INDIA. 
that the temperature-difference is least , and that it is greatest at the change of the 
monsoons. We have also seen that where the anti-monsoon current descends in greatest 
volume, viz. the plains of Upper India, is the coldest part of India at that time of year ; 
and the temperature-difference between Chuckrata and Roorkee is then not only at its 
annual minimum, but it is also less than between Darjeeling and Goalpara, where the 
descent of the anti-monsoon is but little felt. The conclusion is obvious. Any change 
of temperature that may arise from dynamic causes is completely neutralized by other 
causes operating in a reverse direction, and the residual excess of the opposite effects 
are at their maximum when these dynamic causes are most active. This is in entire 
accordance with the conclusions of a 'priori reasoning, and consistent also with the view 
that differences of temperature are the principal cause of wind. 
Dr. Muhry, in a recent work on the winds (Untersuchungen fiber die Theorie und 
allgemeine Geographische System der Winde, page 99), attributes the heat and 
dryness of the westerly winds of the Gangetic plains between March and June in a 
great measure to dynamic heating ; but his view of the origin of these winds is 
certainly erroneous. He adduces them as an example, on a great scale, of an air -cascade 
flowing from Tibet over the ridge of the Himalaya, and a retroversion of the current in 
the hollow of the fall ( Windschatten). I transcribe the passage in a footnote *. Of the 
existence of a north-east current across the crest of the Himalaya, I can find no evidence 
in the account of any traveller in high Himalayan regions. From the accounts of Dr. 
Hooker, General Strachey, M. Schlagintweit, Mr. Shaw, and others, it appears that 
amid all the local irregularities due to the varying direction of the valleys, the prevalent 
winds are southerly up to the principal range, and that day winds of great force, attri- 
buted by General Strachey to the heating of the elevated plains, blow in the same 
direction through the passes. Only in Turkistan does the prevalent wind appear to be 
northerly up to the Mustakh or Karakoram range. The hot westerly winds of the 
Gangetic plain and an extensive region to the south, in April and May, are, as Dr. Hooker 
long ago pointed out, essentially day winds, and due to the heating of the soilf . Were 
* “ In Asien gibt zunachst der Himalaya, Gelegenheit zu Entstehung eines grossen Beispiels unserer Erschei- 
nung auf dem Continente ; so scheint wenigstens ein gewisser endemischer Wind im nordlichen Ostindien seine 
Erklarung zu finden. Langs der siidliclien Seite dieses machtigsten Gebirges, welches ja ebenfalls nach Nordwest 
hin streieht, etwa yon 27 ° bis 35° N., ist wohl bekannt, dass in der heissesten Zeit, im trockenenEriihjahr, von 
Marz bis Mai, zur Zeit, wenn in iibrigen Ostindien, und man kann sagen in iibrigen Siid-Asien, der Nordost- 
monsun herrscht, das ist der Polarstrom, noch ungestort in seiner untersten Schicht durch den sommerlichen 
Seewind, den S.W. Monsun, dass dann das ganze Gangesthal hinunter ein N. W. anhaltend weht, warm und von 
excessiver Trockenheit. Es darf uns kaum Zweifelhaft erscheinen, dass dieser Wind gleichfalls einen Windfall 
und Betroversion des N.O. Passats darstellt.” It is doubtless owing to the dearth of information hitherto 
accessible on the subject of the normal winds of India, that Dr. Muhey has been misled into the belief that N.E. 
winds are generally prevalent in India between March and May. The idea that a polar stream flows from 
Central Asia across the Himalaya is an error of old standing. 
t These winds form a very interesting subject for investigation, but I cannot attempt it at present. They 
must be considered in connexion with the diurnal variation of temperature and pressure. In connexion with 
the latter, I may mention that they generally set in at the time of the morning maximum, and I expect their 
explanation is to be found in a study of the barometric tides. 
