THE COMPOSITE FAMILY 



69 



The diminished atmospheric pressure is always accompanied 

 by a decrease of the temperature in the shade and an increase 

 of the heat of the radiant sun. It also gives rise to great changes 

 of temperature at day and at night. On the Kudremukh, a 

 mountain of the Western Ghats, 6215 feet high, the thermometer 

 stands in the month of April often at more than 40° C in the 

 sunshine and falls to 14° C. before sunrise. Another effect of the 

 rarefied air is the intensity of the sunlight. 



Owing to its low temperature the air cannot hold so much 

 water-vapour as the hot air in the plains. The vapour rising 

 with the hot air from the plains is condensed when it reaches 

 higher altitudes, giving rise to increased rainfall on the moun- 

 tains. On the other hand, the thinner atmosphere contains less 

 vapour and is often 

 exceedingly dry. The 

 result is rapid changes 

 in the humidity of the 

 air. 



The daily changes 

 of the upward and 

 downward currents of 

 air cause a continual 

 movement of the atmo- 

 sphere. 



The rarefication of 

 the air, the intense 

 radiation, the occasion- 

 al dryness of the air, 

 and the constant wind, 

 all tend to produce 

 intense evaporation, 

 which every tourist will 

 experience : everything 

 dries up rapidly, the 

 sweat on the skin eva- 

 porates, the skin becomes dry and brittle, and the sense of thirst 

 is intensified. 



Fig. 71. — Leaf-rosettes of Anaphalis oblonga. 



