II. Note on some winter thermometric observations in the Alps
During the past winter, I spent a. fortnight at the village of Davos, Canton Graubünden, Switzerland, and had thus an opportunity of experiencing some of the remarkable peculiarities of the climate of the elevated valley (the Prättigau) in which Davos is situated. The village has of late acquired considerable repute as a climatic sanitarium for persons suffering from diseases of the chest. So rapidly has its reputation grown, that while in the winter of 1865—66 only eight patients resided there, during the past season upwards of three hundred have wintered in the valley. The summer climate of Davos is very similar to that of Pontresina and St. Moritz, in the neighbouring high valley of the Engadin—cool and rather windy; but so soon as the Prättigau and surrounding mountains become thickly and, for the winter, permanently covered with snow, which usually happens in November, a new set of conditions come into play and the winter climate becomes exceedingly remarkable. The sky is, as a-rule, cloudless or nearly so; and, as the solar rays, though very powerful, are incompetent to melt the snow, they have little effect upon the temperature, either of the valley or its enclosing mountains ; consequently there are no currents of heated air; and, as the valley is well sheltered from more general atmospheric movements, an almost uniform calm prevails until the snow melts in spring.
