The relative humidity of the atmosphere was usually very small, the 
difference between the wet and dry bulbs generally exceeding ten degrees, and 
not infrequently exceeding fifteen degrees. 
June. 1909. Lan-chou Fu. Alt. 5106 ft. 
June was decidedly hotter than May, and the rainfall was greater. The 
prevailing wind was no longer in the east, but blew from the north-east. 
On the gth, at 3.30 p.m., a fierce gale swept up from the west, tearing 
branches off the trees and carrying them for considerable distances. No 
serious damage was done, however. A strong wind and a dust storm were 
recorded on the roth; a strong wind on the 11th; and another on the 12th. 
During these three days of disturbance the barometer fell from 24°90 inches 
to 24°68 inches, rising once more to 25.06 inches. On the rath rain fell, and 
continued intermittently till the 17th. Heavy rain was also reported by two 
members of the party at work in the mountains to the south of Lan-chou on 
the 12th and 13th; whilst a heavy deluge, preceded by a violent wind, was 
recorded by one of them on the 14th. Rain was again recorded on the 15th 
in the same district, while a little to the east of this position heavy rain was 
recorded on the zoth. On the 22nd a west wind was noted, followed by 
rain, and again on the 26th a west wind brought up rain clouds, when ‘72 of 
an inch of rain was recorded in sixteen hours. The wind continued to blow 
from the west for two days, then, shifting right round to the east, seemed to 
bring back the rain clouds. 
It must here be noted that rain was frequently brought up by a north- 
easterly wind. The fact that the Yellow River flows in a north-easterly direction 
from Lan-chou Fu may account for this. It cannot be doubted that the 
Kokonor has some effect upon this district, but it is equally certain that it is 
not the only agency at work, and an analysis of the wind direction and 
corresponding periods of rain leads to the idea that the large volume of water 
flowing down the bed of the Yellow River is another powerful element in the 
meteorology of the district. Only on very rare occasions (in April) was rain 
recorded from any quarter but north-east and west. The total rainfall for the 
month was 1°14 inches, notwithstanding the fact that on five occasions 
the fall was not measured. 
Clouds appeared every day of the month. Cumulus formations pre- 
dominated, though stratus clouds were not infrequent, cirrus clouds occurred 
more often than in May. 
The maximum temperature was go’o° F. on the 26th and 2oth. The 
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