EXTREME HEAT AND TORNADOES. 267,. 



appear above the horizon than it scorched us merci- 

 lessly. In the daytime the heat enveloped us on all 

 sides, above from the sun, below from the burning- 

 ground ; the wind, instead of cooling the atmosphere, 

 stirred the lower strata and made it even more 

 intolerable. On these days the cloudless sky was of 

 a dirty hue, the soil heated to 145° Fahr., and even 

 higher where the sands were entirely bare, whilst at 

 a depth of two feet from the surface it was 79°. 



Our tent was no protection, for it was hotter 

 within than without, although the sides were raised. 

 We tried pouring water on it, and on the ground 

 inside, but this was useless, in half an hour every- 

 thing was as dry as before, and we knew not whither 

 to turn for relief. 



The air, too, was terribly dry ; ^ no dew fell, and 

 rain-clouds dispersed without sending more than a 

 few drops to earth. We observed this interesting 

 phenomenon several times, particularly in Southern ^ 

 Ala-shan near the Kan-su mountains, where the 

 rain, as it fell, met the lower heated atmosphere and 

 passed off in steam '"^ before reaching the earth. 

 Thunderstorms rarely occurred,^ but the wind was 

 incessant night and day, and sometimes blew with 

 great violence, chiefly from the south-east and south- 

 west. On calm days tornadoes were frequent about 

 the middle of the day or a little later. To avoid the 



^ The difference between the wet and dry bulbs of the thermometer 

 Avas sometimes as great as 39°, with the temperature at 1 1 3°. 



- This phenomenon only occurred when the clouds were too small 

 to cool the atmosphere sufticiently. 



' Only three times in July. 



