CHEMICAL AND PHYSICAL NOTES. 166 
“It has been most observed in the valleys stretching in a northerly 
direction from the main summit line of the chain of the Alps and takes 
the form of an abnormally warm wind blowing from the mountains 
towards the plain. It has largely occupied the attention of continental 
meteorologists, and more particularly it has been the subject of exhaus- 
tive investigations by Hann, who has shown by very strong evidence 
that its high temperature must be due to its compression in descend- 
ing from a great altitude. In the descriptions of the Féhn, attention 
is almost exclusively directed to the high average temperature of 
the air, and no mention is made of its extraordinary variations, 
although every observer must have noticed them. They are so great 
as to be recognised at once by the sensations and at the same time so 
rapid as to elude almost every other method of estimation or measure- 
ment. It has also, I believe, not been before remarked that the true 
Foéhn occurs in our own country and with its characteristics quite 
as well marked as in Switzerland. It is sometimes supposed 
that a great absolute height of mountain chain is required for its 
production; but this is not so. A relative height of 1000 to 
1200 metres is quite sufficient for its production; and this is 
equally available on the west coast of Scotland and on the northern 
slopes of the Alps. 
“Some observations were made in the summer of 1893, which was 
abnormally warm all over the north of Europe. In the beginning of 
July I observed the Féin at Fort William, and in the latter part of 
August in the upper Engadine, and more particularly in the valley 
occupied by the Morteratsch glacier. Besides the observation of the 
varying temperature of the air itself, the investigation of the tem- 
perature gradient set up between the melting ice surface of the 
glacier and the hot winds blowing over it presented considerable 
interest. The curious fact was observed that while the hot wind 
was blowing over the glacier and melting the surface in abundance, 
the temperature of the air, as close to the ice as a thermometer 
could be applied without touching the ice, was never lower than 
5°°5 C. 
“In the beginning of July at Fort William the weather was very 
warm, and in the midst of very warm air still hotter blasts made 
themselves felt from time to time. The sensation was much the 
same as is produced when, on the deck of a steamer, the air passing 
the funnel strikes the face. These hot blasts lasted only for one or 
two seconds, and repeated themselves every minute or two. Their 
effect on a thermometer, freely exposed in the shade, was to keep the 
mercury in a constant state of motion, the temperature rising often 
