294 THE POPULAR SCIENCE MONTHLY.
than in much less cold air which impinges with considerable velocity upon the surface of the body. The effect of motion through the air upon the sensation of warmth and cold at Davos is very striking. Sit- ting perfectly still in the sunshine, the heat in midwinter is sometimes almost unbearable ; on rising and walking about briskly, a delicious feeling of coolness is experienced ; but, on driving in a sledge, the cold soon becomes painful to the unprotected face and hands.
Such are the conditions prevailing at Davos, and producing the delightful climate of this winter resort. They may be thus briefly summarized : 1. Great elevation above sea-level ; 2. A continuous, and, during winter, permanent covering of snow ; 3. A minimum of watery vapor in the air ; 4. A clear sun ; 5. A clean atmosphere, free from zymotic germs, dust, and fog ; 6. A sheltered position, favorable for receiving both the direct and reflected solar rays.
I have been thus particular in describing these conditions in order to make clear the capability of the Yellowstone plateau to provide a similar beneficent winter climate for invalids.
From my own observations, and from inquiries made on the spot, I am of opinion that the Yellowstone National Park possesses, in a high degree, all these essential conditions. In elevation above the sea it surpasses Davos ; the great plateau of the park is between 7,000 and 8,000 feet above sea-level, while it is stated that not one of the narrow valleys dips below 6,000 feet. The mountain-ranges, partly surround- ing and partly within the park, rise to heights of from 10,000 to 12,000 feet. I should anticipate, therefore, that all the advantages which, as a winter resort for invalids, Davos possesses from its elevated position, would be enjoyed even in a greater degree in the Yellowstone Park. The period of permanent snow is longer, so that invalids could remain there probably until the end of April, whereas the melting of the snow generally compels them to leave Davos early in March, when the climate of the valleys is peculiarly unfavorable for chest-com- plaints. It is to be expected, from its greater elevation, that a still clearer sky and a larger proportion of sunny days would be experienced in the Yellowstone Park, while the wholesomeness of the air would be still more marked, owing to its comparatively greater freedom from zymotic matter.
The latitude of Davos is 47, and the Yellowstone Park lies almost entirely between the forty-fourth and forty-fifth parallels. The winter temperature at Davos varies from 32 Fahr. down to 22 Fahr., and that of the park would probably observe nearly the same extremes. The selection of suitable sites for hotels and sanitary dwellings is, of course, of the highest importance. The only hotel at present existing the Mammoth Hot Springs Hotel is not favorably situated, but, even in my comparatively limited excursions in the park, I saw numerous most eligible sites for such establishments sites sheltered from north- erly winds, either by abruptly elevated ground or pine-forest, with a