Again the barometer showed considerable fluctuations, the highest readings 
being 25°27 inches, and the lowest 24°72 inches. The average of all readings 
was 25°00 inches. 
The highest temperature during the month was 83°0° F. on the 25th, 
and the lowest was 30°0° F. on the 7th. The averages were 68°6° F. for the 
maxima and 41'2° F. for the minima. The temperature steadily 
increased throughout the month, though one or two cold days were 
experienced towards the end. 
May, 1909. Lan-chou Fu. Alt. 5106 ft. 
With the exception of six days, which were spent in the mountains to the 
south of Lan-chou, a very complete set of observations was made during the 
month of May. 
The observations differed but little from those made in April. 
The temperature was increasingly warmer, the barometer averaged a 
little higher, but was perhaps a trifle more unsteady; whilst there was more 
rain, more strong winds, and slightly greater variety in cloud formation, 
stratus clouds appearing more frequently. 
The prevailing wind was again in the east, though winds from the north- 
east and north-west were recorded with some frequency. 
Rain fell on eight occasions; the rainfall, which was recorded on four days 
only, being 00g of an inch. Late in the afternoon of the 11th a remarkable 
phenomenon was noticed. Two strong winds, blowing from the west and 
east respectively met over Lan-chou, when hail and rain fell for about an hour. 
This was followed by rain during the night, fog next day, and snow upon the 
surrounding hills, and it may be noted that a wind from the west was largely 
responsible for the latter. Most of the rain that was recorded fell during these 
few days of atmospheric disturbance. The temperature fell to considerably 
below the average, whilst the barometer ran up to the highest level recorded 
during the three and a half months’ stay in Lan-chou. It may 
here be noted that whenever the temperature was unusally low the barometer 
was high, and vice-versd. 
The average maximum temperature was 75'5° F., and the average 
minimum was 48°7° F., the highest and lowest temperatures being respectively 
880° F. on the 30th and 350° F. on the 13th. 
The barometrical readings averaged 25°07 inches, a slight increase on 
that of the April readings, while the highest point reached was 25°30 on the 
13th and the lowest, 24°78 inches, on the 28th. 
148 
