586 
ME. H. F. BLANFOED ON THE WINDS OF NOETHEEN INDIA. 
Schlagintweit’s charts in the 153rd volume of the Philosophical Transactions. But 
the Messrs. Schlagintweit’s division of the year into four equal periods does not admit 
of the phenomena being represented in sufficient detail for the present purpose ; nor does 
it accord with the natural arrangement of the seasons, which in Northern India present 
only three distinct phases. These are : — (1) the cold season , lasting from the breaking 
up of the rains in October to February or March ; (2) the hot season , characterized 
in general by a dry atmosphere and a great diurnal range of temperature ; and (3) the 
rainy season, in which the temperature is moderately high and equable and the air very 
humid. The beginning and ending of these seasons differ in period somewhat in different 
parts of the area, and the gradations of temperature which accompany them are very 
different both in period and amount. In describing these latter it will be convenient to 
take the month of October as our starting-point. Except where otherwise specified, 
the figures quoted in the following description of the horizontal distribution of tempe- 
rature are those of Table III., viz. the sea-level equivalents of the observed mean tem- 
peratures. 
At the close of the rains in the early part of October (Plate XL VII.), the temperature 
of Northern India is nearly uniform at about 81° or 82°. But changes soon set in : 
evaporation and radiation to a cloudless sky speedily reduce the temperature of the 
more elevated plains of the interior below that of the maritime belt ; and thus the 
average temperatures of the whole month, given in Table III., show an extreme varia- 
tion of 8°. In the two following months the inequalities thus arising become greatly 
intensified; and they culminate in January, when there is a difference of nearly 20° 
between Mooltan and Bombay. The distribution of temperature in this month is shown 
in the chart (Plate XLIII.), on which the isotherms are interpolated from the figures 
given in Table III., with some additions in particular cases. Without insisting on small 
differences, which may be subject to correction on the review of a longer period and 
with more accurate coefficients of the temperature correction for altitude, it is clear that 
the Punjab is in January the seat of the greatest cold, while Rajpootana on the one 
hand, and the Gangetic delta and Lower Assam on the other, are warmer than the 
regions immediately adjacent under the same latitudes. The difference of the mean 
temperature of the Punjab stations (55°) and that of Calcutta, Berhampore, and Goalpara 
(66°) is not less than 11°. The great Gangetic plain, lying between them, enjoys a 
nearly equable temperature throughout of 60° or a little under. Benares in this month 
appears to have a lower temperature (for its elevation) than Roorkee, and very much 
lower than Goalpara, both in higher latitudes. Opposite to the Gulf of Cambay and 
the Bay of Bengal, especially the latter, the isotherms advance northwards, retreating 
anticipate a somewhat higher temperature in the neighbourhood of the hills, where, as I suppose, the anti- 
monsoon current descends to a lower level than further south. It is true that the isotherm of 65°, as laid down 
on the chart, shows no corresponding loop where it might be expected to occur ; but I have no observations for 
determining this part of its course nearer than Hazareebagh, which is at an altitude of 2000 feet. 
