XVII. The winds of Northern India, in relation to the temperature and vapour-constituent of the atmosphere

It is my object in this paper to describe the normal wind-currents of Northern India and their annual variation, and to trace out their origin and causes, in so far as these can be discovered in the local physical changes of the atmosphere. For this kind of inquiry India offers many peculiar advantages. At opposite seasons of the year it exhibits an almost complete reversal of the wind-system and of the meteorological conditions depending on it or on which it depends; its almost complete seclusion, in a meteorological point of view, from the remainder of the Asiatic Continent, by the great mountain-chain along its northern border, simplifies, to a degree almost unexampled elsewhere, the conditions to be contrasted by limiting them to those of the region itself and of the seas around; while it presents in its different parts extreme modifications of climate and geographical feature. In its hill-stations it affords the means of gauging the condition of the atmosphere at permanent observatories up to a height of more than 8000 feet, and in the loftier peaks and ridges of the Himalaya, at temporary observing-stations, up to the greatest elevations to which man can ascend when unaided by the balloon. The periodical variations of temperature, vapour-tension, pressure, &c., both annual and diurnal, are strongly marked and regular; and their changes proceed so gradually, that the concurrence and interdependence of their several phases can be traced out with much precision, even in the unanalyzed registers. These numerous and great advantages indicate this country as preeminently a field for the future study of meteorology. Most of the great problems of the science are here presented in the form of instantiœ ostensivœ; and comprehensive systematic observation, intelligently conducted, is all that is wanting to place them at the command of European science.