Edward Frankland

“ I allude to that most interesting tract of territory—the Yellowstone National Park.
The beneficial effects of a winter climate like that of Davos depend upon the concurrence of several conditions which are difficult to secure at a lower elevation than that just indicated. In the first place, the sun's rays are far more powerful at great than at low elevations, and their intensity is much more equable throughout the day; thus the temperature in sunshine observed by me at Davos on the 26th of December was 89·2° Fahr. ”

“ Sitting 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 ”

“ An almost uniform calm, therefore, prevails during the continuance of snow. This immunity from air-currents is of the highest 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 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. ”

“ The very high sun-temperature observed on the Diavolezza was recorded at a station surrounded by snow-fields in brilliant sunshine, and the thermometer was placed upon snow.
Not only is solar radiation much more intense at great altitudes, but it is also more equable during the whole day, inasmuch as the comparative absence of suspended matters in the air renders the thermal power of the rising and setting sun more nearly equal to that of the meridional sun. Thus it has been observed that, at or near the sea-level, the sun-temperature increases about 15° Fahr. ”

“ The most important influence upon the sun-temperature, however, is the reflection of solar rays from the snow. The valley of Davos has precipitous sides and a flat sole, and the hotels are situated on the northwest slope of the valley; consequently they receive, in winter, the scattered solar rays reflected from a large area of snow. A considerable proportion of the thermal rays of the sun falling at an acute angle upon a surface of snow is known to be reflected. ”

“ 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-complaints. 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. ”

“ At present, the park, so generously set apart by Congress for the enjoyment of the American people, is utilized only by a very limited number of tourists, in the few months of a very short summer, and it seems a pity that such a magnificent possession should not be much more extensively used. ”

“ On the other hand, the absence of suspended watery particles in the air has, no doubt, very considerable influence in preventing the chilling of the skin. Not only are such liquid particles present when there is visible fog, but they often exist in great numbers when the air presents a perfectly transparent appearance. ”

“ The excessive dryness of the air at Davos has probably but little special influence upon the sensation of heat and cold, because the maximum proportion of aqueous vapor present in air near the freezing-point is everywhere small, and the specific heats of equal volumes of air and aqueous vapor are not widely different. ”

“ Moreover, an elevation of 5,000 or 6,000 feet places us, especially in winter, to a great extent above the region of cloud, and thus enables us to enjoy a bright sun at time when clouds effectually cut off his rays from lower altitudes. ”