44,4, REPORT—1904. 
2. Statement of abnormal features of the meteorology of that area for the 
unique period 1892-1902 illustrating the remarks in the preceding sketch. 
3. Suggestion of the co-ordination of the meteorological observations of the 
British Empire and the creation of a central office for the investigation of problems 
of general meteorology. 
India is the most typical example of monsoon conditions, that is, of opposite air 
movementsof six-monthly period which, in its case, depend on the annual temperature 
changes in the sea and land areas of the Indian Ocean and continent of Asia. The 
monsoon conditions in India are intensified by its unique position and topography. 
It projects southwards into the Indian seas over 15° of latitude, and is protected 
northwards by the vast barrier of the Himalaya Mountain range and Thibetan 
plateau. The axis of the Himalayan range is at least 2,000 miles in length and 
has an average elevation of over 20,000 feet. ‘The extent of country over 10,000 
feet in elevation to the north of India is from 300 to 500 miles in width. These 
figures will give some idea of the magnitude of India’s northern barrier. 
During one period of the year there is an outflow in the lower atmosphere from 
land to sea. The direction of the lower air drift in India is determined in part by 
the lie of the mountains and river valleys, and is from north-east over the greater 
part of the Indian seas. January is the month most typical of this air movement 
and of the accompanying weather conditions. 
During another portion of the year the lower horizontal air movement is from 
sea to land. This movement is much steadier and more powerful and influential 
in every respect than the former. July and August are the months most repre- 
sentative of the totality of the weather conditions of this period, 
Conditions similar to those of January prevail in their entirety from about the 
middle of December to the end of February or middle of March—the period known 
in India as the cold weather or cool season. The lower horizontal air movement 
in India during the period has its origin in Upper India, where it is very feeble, 
and whence it increases seawards and is of moderate force in the Bay of Bengal 
(mean force 2 to 3, Beaufort scale) and the Arabian Sea (mean, 2 to 4). It is fed to 
acertain extent by drift down the river valleys, and passes in the North-west India 
frontier hill ranges. There is, on the other hand, no general drift down the 
Himalayan river valleys or across the main ranges from Central Asia, The normal 
air movement in the Western Himalayas (and perhaps the whole range) is an 
alternating up and down, or day-and-night movement, depending upon the diurnal 
heating and cooling of the plains of Northern India, Hence India (in its lower air 
movement) is at this time completely shut off from Central Asia. 
The lower air movement is continued over the Indian seas southwards to a 
region of vertical movement over a narrow belt a little to the south of the equator. 
This belt is also the goal of the lower air movement of the south-east trades 
circulation at this time. The equatorial belt of calms is hence the termination of 
the lower air movement of the south-east trades and north-east monsoon. It 
is chiefly an area of uptake, and of outflow northwards and southwards, to 
replace the lower air in flow from the distant south and north. The influx to the 
Indian land area occurs chiefly or entirely in the upper and (perhaps) middle 
atmosphere. There is also, as indicated by the wind directions in the lower 
Assam and Burma hills, an influx from the adjacent seas in the upper portion of the 
lower atmosphere.' The diurnal land and sea breezes alternate with great regularity 
on the west coast south of Gujarat during this period, but probably do not contri- 
bute to the general upper influx compensating in part or whole the lower outflow. 
The circulation over the Indo-oceanic region hence consists at this time of two 
semi-independent circulations, with a common sink or goal for the lower air 
movement, which shifts with the season and with the relative strengths of the 
two movements. It is hence probable that they react on each other to some 
extent, and possible that general abnormal actions may affect the two similarly. 
' In India the lower atmosphere may be defined as from 0 to 5,000 feet, the 
middle atmosphere from 5,000 to 15,000 or 20,000 feet, and the upper atmosphere 
above 20,000 feet, 
