358 MR. S. A. HILL ON THE WINDS OF NORTHERN INDIA, AND THEIR 
The pressures given in Table XI. do not need any special correction for daily range, 
because in every part of India the mean height of the barometer between 10 and 16 
hours does not differ by more than a few thousandths of an inch from the mean of the 
twenty-four hours, and it will be seen immediately that, with the unavoidable uncer¬ 
tainty there is as to temperature, it is unnecessary to take such small differences 
into account. 
It has already been pointed out, in discussing the probable height to which con¬ 
vection currents extend at the hottest time of the day, that nothing accurate is 
known regarding the decrease of the day temperatures with height above the sea in 
the free atmosphere. But, by taking the differences between the day temperatures 
given in Table XII. for stations in North-Western and Central India and the sea- 
level values of the mean temperatures of the same places, published in vol. 2 of the 
‘Indian Meteorological Memoirs,’ pages 137-141, and combining the results into 
groups for stations below 2000 feet, between 2000 and 5000 feet, between 5000 
and 8000 feet, and above 8000 feet, we can construct a set of curves giving the 
variations of temperature on mountain slopes, unaffected by changes of latitude or 
longitude. By graphic interpolation we can, then, get from these the rates of decre¬ 
ment. The results for the four months in the Table are shown in Table XIII. They 
exhibit a considerable diversity of character, and a tendency in the summer to an 
increase of temperature with height at the greatest elevations, owing to the greater 
diurnal range of the thermometer at Leh than at the stations on the outer ranges 
about 7000 feet elevation, whilst it is practically certain that there is no such 
tendency in the free atmosphere. 
Table XIII.—Vertical Decrement of Day Temperature on the Mountains of Central 
and North-Western India. 
Height. 
January. 
May. 
July. 
October. 
O 
O 
O 
O 
0 to 
1,000 feet . . 
4'4 
7-3 
60 
4-6 
1,000 „ 
2,000 „ ... 
3-4 
6 1 
5'3 
47 
2,000 „ 
3,000 „ ... 
27 
57 
4-6 
38 
3,000 „ 
4,000 „ ... 
2-2 
47 
4-0 
28 
4,000 „ 
5,000 „ ... 
1-8 
3-2 
3'4 
2-4 
5,000 „ 
6,000 „ ... 
1-6 
2-3 
2-8 
17 
6,000 ,, 
7,000 „ ... 
1-6 
1-5 
2-3 
1*5 
7,000 „ 
8,000 „ ... 
17 
0-8 
1-9 
1-4 
8,000 „ 
9,000 „ ... 
1-9 
07 
1-5 
1-5 
9,000 „ 
10,000 „ ... 
27 
0-5 
17 
1-6 
0 to 10,000 feet 
23-4 
30-0 
32-9 
25-4 
The total decrement between sea-level and 10,000 feet is less in every month than 
that found by Glaisheb in the free atmosphere over England and France, as was to 
