74 



different parts of the vallej'-, and consequently I have found 

 it best only to note whether the wind blows up or down the 

 valley. The most frequent wind here has a direction from 

 the lake to the lower part of the valley and on one house 

 will show itself as a north wind, while a few houses further 

 on it will, according to the position, be north-east or north- 

 west. 



Besides this, the valley wind is really a surface wind, so 

 that very frequently the smoke shows the direction to be 

 from the north at the height of the roof, whereas at about 

 double or three times this height it is blowing from the 

 south. This occurs so often that it may almost be considered 

 a rule when a true valley wind is blowing. Also it is often 

 the case that in the middle of the valley the wind is from 

 the north while at the two sides it is from the south. There 

 must therefore on these occasions be a neutral zone, and the 

 force must vary very greatly at different heights. This I 

 have been able to see clearly, for on one or two days when 

 there was a strong unpleasant wind by the ground, a vane 

 on a pole about the height of a house showed no movement. 

 In the two lateral valleys, Dischma and Fluela, it very often 

 happens tliat the wind is blowing in opposite directions, 

 probably in these cases the wind may either be caused in 

 these side valleys, or be drawn by the main valley. 



The direction of the prevailing valley wind depends upon 

 various circumstances, and it has been a matter of scientific 

 surprise to some people that the direction in Davos should 

 be down the valley, and the cause has often been sought in 

 the wrong place, but it seems to me that the explanation is 

 a simple one, for although the direction is from N.E. to 

 S.W. the main mountain masses lie to the south, so that the 

 air being more warmed over these mountain masses the 

 current is thus drawn to the south although the valley falls 

 in this direction. That this is the probable explanation 

 receives the strongest support from the lower part of the 



