A GREAT AMERICAN WINTER SANITARIUM. 293 



White paper 116-6 Fahr. 



White linen 116-1 " 



Snow lll'O " 



Metallic minor 9r5 



Common mirror 9 < '5 



Light-colored soil 96-3 



Parched grass ^5'3 



Gray rock 884 



Green grass 88 - 2 



Clack silk 84-0 " 



Black caoutchouc 82"2 



Black merino 80 - 4 



White paper and white linen were therefore the most perfect re- 

 flectors of solar heat ; but the efficiency of snow was but slightly infe- 

 rior, while it greatly surpassed that of even polished metal. 



The relative proportions of direct and reflected solar heat, falling 

 upon a body in sunshine surrounded with snow, has not been deter- 

 mined, although it has been ascertained where water is the reflecting 

 surface. Thus, M. Dufour has measured the proportions of direct and 

 reflected solar heat incident at five different stations on the northern 

 shore of the Lake of Geneva. He found that the proportion of reflected 

 heat was as much as sixty-eight per cent of the heat directly incident 

 from the sun, when the sun's altitude was between 4 38" and 3 34". 

 At about 70 altitude, the proportion was between 40 and 50 of re- 

 flected to 100 of direct heat ; and, even at an altitude of 16, the pro- 

 portion was between 20 and 30 of reflected to 100 of direct heat ; but 

 when the sun was higher than 30 the reflected heat was hardly appre- 

 ciable. My own observations confirm these results, for I found at 

 Alum Bay, Isle of Wight, that the reflection from a ruffled sea, at 6.45 

 p. m., in May, added no less than forty-four per cent to the direct solar 

 heat. 



It is obvious, therefore, that the Davos sanitarium is much indebted 

 to its snow-covered valley for a winter day-climate which is so genial 

 as to allow the patients to spend nearly the whole of every sunny day 

 in the open air, although the temperature of the air may be 15 or 20 

 below the freezing-point. Five minutes after sunrise, many of the 

 patients walk in the open air without any special wraps, and some of 

 them even without overcoats. In the brilliant sunshine, one feels 

 comfortably warm sitting in front of the hotel in a light morning coat. 



3. Freedom from Air-Currents. Davos is well sheltered from 

 general atmospheric movements, and, as the surrounding snow can not 

 be warmed above the freezing-point, no local currents or valley- winds 

 can be set up. An almost uniform calm, therefore, prevails during the 

 continuance of snow. This immunity from air-currents is of the high- 

 est importance to the patients, for, without it, they would not be able 

 to sit out-of-doors and enjoy the free and comparatively germless air 

 as already described. In still though cold air the skin is less chilled 



