March the oth when an east wind was blowing, the difference between the bulbs 
was 34°2° F. 
Snow was recorded eleven times and rain three times during the journey. 
As already stated, both were proportionately more frequent when the wind was 
in the west, in which direction lies Kokonor, the great lake of Eastern Thibet. 
It may be that the snow clouds originate in this district. Hoar-frost was 
recorded from time to time. 
April, 1909. Lan-chou Fu. Alt. 5106 ft. 
When the expedition reached Lan-chou Fu on April 5th, that city, and 
the district generally were suffering from a protracted period of drought. 
According to native reports there had been no rain to speak of for three years. 
Judging from the extreme bareness of the country with its parched sun-baked 
hills and valleys this might well be the case. 
It seems as if the desert were slowly creeping in from the north and 
north-west. It was stated by more than one of the Europeans, long resident 
in the district, that ten years ago the country immediately north and north- 
west of the city for ten or more miles was fertile. Year by year this fertile 
area has decreased till the whole of the country north of the Yellow River, 
which flows under the northern wall of Lan-chou, has become a howling 
wilderness, without a vestige of green anywhere. The expedition found the 
country south of the river for some twelve miles in a condition scarcely better 
than that of the country to the north and north-west. 
During the months that the expedition spent at Lan-chou the drought 
broke up, and towards the end of June and in the beginning of July rain fell in 
great quantities. 
Thus the season cannot be considered as a normal one, its commencement 
being towards the end of a three years’ drought and its termination coinciding 
with that of the drought, and with general atmospheric disturbances. 
During April the weather was dry, and generally speaking fine. Wind 
was recorded daily, whilst clouds were noted most of the time. The prevailing 
wind was from the east, which blew with more or less strength on fourteen 
days. Once it shifted to the south-east but at other times it was either from 
the west or north-west. 
Cumulus and cirro-cumulus clouds prevailed throughout the whole month, 
cirrus and stratus clouds being recorded but once each. Dust hazes were 
frequent and on the 13th a dust-storm was recorded. 
Towards the end of the month a little rain fell. 
147 
