132 MR. W. B. HEMSLEY ON THE 
quickly disappears. At the end of November the Hoangho was 
frozen; the ice, however, was not permanent and was already 
melted in February. The temperature at 1 p.m. in February was 
54°°9, March and April 77°°5. During the night in February it 
fell to —11%2, in April to 19°4. 
The dryness of the air, the violent winds, and the cold nights 
much retard the growth of herbs and trees. In Amdo, in the 
valley of the stream Rako Gol, flowing into the Sining, the first 
herb, the dwarf Gentiana squarrosa, opened its flowers at the 
begiuning of April, and the leaves of trees and shrubs began to 
unfold about the same time. In the highest gorge of the River 
Yedsin so late as June Ist only ten species of flowering plants 
were collected ; and in elevated exposed places at that date not 
even traces of vegetation were visible. In the zone of alpine 
meadows flowers were produced from the end of June to the end 
of August. On the Nan Schan Mountains the thickets and, by 
the middle of August, the meadows have an autumnal appearance. 
In the desert of Odontala, North-east Tibet, the first flowers 
opened in tbe beginning of June, but in a cautious manner, as 
they scarcely appear above ground ; indeed, up to this time they 
have been covered by their leaves. In the Mur-ussu valley 
flowering herbs are found in the middle of June, but shrubs are 
still naked, and only in the beginning of July do they begin to 
put forth leaves. 
Tsaidam, situated 3000-4000 ft. lower, has a much less severe 
climate; the temperature is warmer, the snow and rain less abun- 
dant, the sky usually clear and storms less frequent, but the 
air is often full of dust asin Mongolia. In the summer clouds 
of obnoxious insects appear, and to such an extent that the 
whole region becomes a desert and the inhabitants, with their 
flocks and herds, go up into the mountains. 
Maximowicz, to whom we are indebted for the greater part of 
the foregoing remarks on the topography and climate of Tibet, 
refers, as already mentioned, more particularly to the north- 
eastern part—the part from which we have the least material. 
For the west we have Strachey and Schlagintweit’s observations 
and data, besides the results obtained by the more recent 
travellers. We may here quote a few sentences from General 
Sir R. Strachey (Journ. Linn. Soc.,Bot. xxx. (1894) p. 101) :-— 
“The climate of these parts of Tibet is very extreme. The air 
