ME. H. F. BLANFOED ON THE WINDS OE NOETHEEN INDIA. 
609 
2. Shillong and Goalpara. 
Goalpara, 
K 
Shillong, 
K 
Difference, 
h i~K 
Mean 
density 
of air, 
d 1 . 
^1+^2 
*l + *2 
2 ’ 
Mean 
density 
of air, 
d 2 . 
January 
29-603 
25-262 
4-341 
0-863 
27*432 
57-8 
0-352 
0-863 
February 
•322 
•238 
•284 
•852 
•380 
60-6 
•354 
•854 
March 
•442 
•211 
•231 
•842 
•326 
67-2 
•404 
•846 
April 
•380 
-195 
•185 
•832 ' 
•287 
70-8 
•513 
•839 
May 
•286 
•098 
•188 
•833 
•192 
73-3 
•662 
•830 
June 
•206 
•060 
•146 
•824 
•133 
74-6 
•747 
•823 
July 
•195 
•058 
•137 
•823 
•126 
75-2 
•774 
•817 
August 
•247 
•100 
•147 
•825 
•173 
75-2 
•789 
•825 
September 
•328 
•172 
■156 
•826 
•250 
73-6 
•744 
•831 
October 
•426 
•247 
•173 
•830 
•333 
70-9 
•642 
•838 
November 
•56 7 
•320 
•247 
•844 
•443 
63-5 
•467 
•856 
December 
•621 
•324 
•297 
•854 
•472 
57-4 
•365 
•868 
Year ,. 
29-402 
25-190 
4-211 
0*837 
27-296 
68-3 
•568 
•841 
Eange 
0-426 
0-266 
0-204 
0-040 
0-346 
17-8 
•437 
•051 
3. Simla and Roorkee. 
Roorkee, 
Simla, 
K 
Difference, 
b~K 
Mean 
density 
of air, 
d v 
Roorkee, 
b v 
Simla, 
b r 
Difference, 
b ± -b 2 . 
Mean 
density 
of air, 
d v 
January 
February ... 
March 
April 
May 
June 
July 
August 
29-126 
•048 
28-985 
•878 „ 
•747 
•632 
•638 
•695 
23-225 
•198 
•197 
. -207 
•142 
•061 
•069 
•101 
5-900 
•850 
•788 
•671 
•605 
•571 
•569 
•594 
0-835 
•828 
•819 
•803 
•793 
•789 
•788 
•792 
September ... 
October 
November ... 
December ... 
Year 
Eange 
•792 
•960 
29-104 
•154 
28-895 
0-522 
•194 
•277 
•293 
•254 
23-185 
0-232 
*598 
•683 
•811 
•900 
5-712 
0-331 
•793 
•804 
•823 
•835 
0-808 
0-047 
From these Tables we learn a fact of high importance, viz. that of the whole annual 
oscillation of the atmospheric pressure over the Gangetic plain, which may be taken as 
the measure of the forces that produce the alternating monsoons of India (up to the 
equator, where the pressure is nearly invariable), nearly one half is due to an alteration 
of the density of that stratum of the atmosphere which lies between 400 and 5000 feet 
(Goalpara and Shillong), more than two thirds to that of the stratum between 400 and 
7000 feet (Goalpara and Darjeeling), and nearly two thirds to that between 800 and 
7000 feet in the North-western Provinces (Roorkee and Simla). If for the actual 
annual barometric range at Goalpara and Roorkee we substitute their equivalents at 
sea-level, as given in Table VIII., viz. 0'445 inch at Goalpara and 0-595 at Roorkee, and 
increase the range of the values of b x — b 2 by a corresponding amount, then the oscillation 
below Shillong becomes more than one half, and that below Darjeeling and Simla nearly 
seven tenths of the whole. 
Further, it is to be noticed that the change of density in the North-western Provinces 
considerably exceeds that in Bengal, and affects the atmosphere to a greater height, 
