1894.] Atmospheric Temperature, especially during Fohn. 117 



The result of the few observations here quoted is to show that the 

 air, which over land has a temperature of 15 to 20 or higher, in pass- 

 ing over a glacier is cooled to a comparatively slight degree. 

 Although the air appears to be thoroughly- mixed by its own motion, 

 very sharp gradients of temperature are produced and maintained. 

 The great and abnormal temperature of the air of the valley is kept 

 up by the heat liberated by the compression accompanying the 

 descent of local streams or striae of air from high levels. These keep 

 up an extra supply of heat over and above what is supplied by the 

 direct radiation of the sun. The result is that the melting of the 

 glacier in Fohn weather greatly exceeds that of even the hottest 

 day of ordinary weather. 



In order to convey a general idea of the climate in the neighbour- 

 hood during the period when my observations were made, I subjoin a 

 table of the air temperatures observed at the Pfarrhaus in Pontresina 

 three times daily, and obligingly supplied to me by Herrn Pfarrer 

 Falliopi. 



Table II. Temperature of the Air at Pontresina. 



In this table the very high temperature on the 18th, 19th, 20th, 

 id 21st is very apparent. The Fohn prevailed during all these days. 



On the 23rd August, which was a very warm day, I made a series 

 :>f observations between Pontresina and the top of the Piz Languard, 

 rhich is the highest peak on the ridge immediately behind Pontre- 



