Chemical and Physical Notes 

 TABLE XXIV. 



129 



and of the wet bulb 6'45, whence we have the vapour tension 4-5 mm. and 

 the relative humidity 47. The weather was of the same kind as in the 

 valley, abnormally warm, and the air very dry." 



NOTE. The Fohn dealt with in this paper is fine-weather Fohn, with 

 cloudless sky and strong sun. The Fohn occurring with overcast sky 

 and rain is not treated. It is this Fohn particularly that wastes glaciers, 

 because it persists through the twenty-four hours, while the melting by 

 the fine-weather Fohn is limited to the four or five hours before and after 

 noon. I have only once witnessed the overcast Fohn and it is a most 

 powerful melting agent, but I am not prepared to furnish a satisfactory 

 mechanical explanation of it. 



Conclusion. It will be observed that in this paper no 

 attempt is made to give instructions to the Chemist and 

 Physicist of the Expedition. Here and there a lead in one 

 direction or another is suggested. He must rely on his own 

 knowledge and experimental ability. Questions or problems 

 which excite his curiosity should be worked out in his own 

 way. If, in this way, he answers or solves them to his own 

 satisfaction, it is probable that he has made a genuine addition 

 to knowledge. In all his work it will be useful for him to 

 remember that, primarily, Physics and Chemistry are branches 

 of Natural History, 



