RELATION TO THE DISTRIBUTION OF BAROMETRIC PRESSURE. 
349 
In Northern Bengal and Assam, at this season, the decrease of maximum tempera¬ 
ture with height is so slow in the first three or four thousand feet, that no rapid 
convective action during sunshine can take place. The observations at Goalpara, 
286 feet, and Darbhanga, 166 feet; at Shillong, 4794 feet, and Kathmandu, 4388 feet; 
and at Darjiling, 7421 feet,* give a combination from which variations in latitude 
and longitude are almost completely eliminated, and from the maximum temperatures 
of these places in May we get the following rates of decrement :— 
o 
Sea-level to 1000 feet.3'0 
1000 „ 2000 „.3-3 
2000 „ 3000 „.3-6 
3000 „ 4000 „.3-9 
4000 „ 5000 „.4-2 
5000 „ 6000 „.4-5 
These are so much slower than those for North-Western and Central India, that 
there is, comparatively speaking, no disturbance of the kind above discussed, and 
accordingly we find that the anomalous hot winds do not usually penetrate into 
Bengal, or become greatly modified in character by mixing with the lower atmospheric 
strata, if thev do. 
During the earlier part of October, south-west monsoon conditions prevail over 
Bengal, and the wind directions are those given by the local pressure gradients ; but, 
towards the end of the month, convection currents, induced by the high range of 
temperature, become active, the day winds at the same time backing from east to 
north and north-west, thus causing the resultant for the month to be almost due 
north. In Central and North-Western India, where this month is characterised by 
clear skies and a large temperature range, there is probably a good deal of convective 
action, as may also be inferred from the afternoon fall of vapour-pressure in this 
month (see Table III.). 
In this region, the mean temperature in October decreases with height above sea- 
level at the following rates :— 
o 
Sea-level to 1000 feet.391 
1000 „ 2000 „.3-69 
2000 „ 3000 „.3-47 
3000 „ 4000 „.3-25 
When these are corrected for the diminution of daily range, which is extremely 
rapid—the decrease, for example, between 1500 feet (the Bajputana plain) and 
4000 feet (Mount Abu) being from about 30° to 15‘—the figures become for the daily 
maxima 
Formerly 6941 feet, but tbe observatory was removed to a new site in 1882. 
