180 
The result of the 89 days of December, January, and Feb- 
ruary (during this time the ground was more or less covered 
with snow when I went to my instrument at 1 p.m.), shows 
that the mean rate from 9 — 1 was 0'608 miles per hour, 
while from 1 to 3 p.m. it was 1-384 miles per hour; that is 
to say that about one-fifth of the wind which blew in the 24 
hours was between 1 to 3 p.m., and nearly all of this will be 
a valley wind* ; and to return to what I before said, this 
will mean that the same air may be blown backwards and 
forwards two or three times over Davos, and thus there are 
great dangers from any drainage carried into the river 
within a few miles of the principal village. 
Smoke. 
There is another thing which I must mention, though not 
belonging to any series of observations, but when here 
before I frequently had occasion to examine the snow and 
smoke microscopically, and at that time the snow really re- 
mained white, and when filtered, hardly gave any deposit, 
as the combustion from the stoves was very perfect and 
nearly all the smoke was microscopic, consisting of small 
particles, in which wood structure could often be seen, but 
now all is changed, for when I filtered snow water to use it 
for evaporation, the filter soon became quite black, and so 
far choked up the filter as to allow the water to pass through 
but very slowly. 
The large amount of smoke which falls upon the snow is 
to a large extent masked, because in our fine weather the 
snow entirely recrystallises down to the ground, within a 
* This winter has been generally still in this district of Switzerland, 
that possibly there is usually more wind than this winter, but we can see 
that it is as a rule but little. The ground was free of snow most of 
March, and therefore the valley wind was stronger. 
Out of 293 times that I went to the anemometer during the three 
winter months, there was no movement at all on 208 occasions (71 per cent). 
At 9 a.m. it was 16 times moving and 74 still. 
At 1 p.m. do. 20 do. 59 do. 
At 3 p.m. do. 44 do. 45 do. 
