A GREAT AMERICAN WINTER SANITARIUM. 291 



It is obvious that this action of extensive reflecting surfaces of 

 snow must exert a powerful influence upon the maximum temperature 

 of places favorably situated for receiving the reflected rays ; and, 

 moreover, where the proportion of heat reflected varies (as it has been 

 proved to do in the case of water, and as it doubtless also does in the 

 case of snow) inversely as the angle formed by the incident rays and 

 the reflecting surface, this action must materially contribute, espe- 

 cially in winter, to the maintenance of an approximately uniform sun- 

 tempei-ature throughout the day. At Davos, and similar elevated 

 stations, however, the comparative freedom of the air from suspended 

 particles must, to a great extent, contribute to such a result ; for, as 

 pure and dry air is transcalent and reflects heat but very slightly, the 

 horizontal sunbeams, passing through such air, would be nearly as 

 powerful as vertical rays. 



The peculiar winter climate of Davos depends, therefore, upon the 

 following: conditions : 



1. Elevation above the Sea. This single condition favors a ge- 

 nial and wholesome winter climate in several ways. In the first place, 

 by reducing the weight of cold air in contact with the body, whereby, 

 even with a much lower thermometer, the air, if still, feels warmer at 

 an elevated station than in the lower and denser regions of the at- 

 mosphere, in consequence of the slower abstraction of heat from the 

 body. In the second place, the air at great altitudes is more permeable 

 to the heating rays of the sun, owing both to its dryness and to its 

 freedom from dust and suspended particles generally. In illustration 

 of this I have made many experiments, chiefly in England and Switzer- 

 land, and an abstract of the results obtained is given in the following 

 table : 



PLACE OF OBSERVATION. 



Oatlands Park, Surrey 



Biffelberg, Zermatt 



Hiirali, Zermatt 



Gornergrat, Zermatt 



"Whitby, Yorkshire 



Pontresina, Engadine 



Bernina Hospitz, Engadine 

 Diavolezza, Engadine 



Air- 

 temperature. 



Degs. Fahr. 

 86-0 



76-1 

 68 2 

 576 



90-0 

 79-7 

 66-4 

 42-8 



It is thus evident that, although the air-temperature continually de- 

 creases as we ascend, the sun-temperature as regularly augments. The 

 horizontal line in the table divides the observations into two groups, 

 in each of which the sun's altitude was approximately the same. In 

 these, and similar observations described further on, the air-tempera- 

 ture was found by placing an ordinary mercurial thermometer upon a 



