Page:Popular Science Monthly Volume 28.djvu/690

672 Since the above was written, the subject has been very graphically presented by means of colored maps, published in the "Report of the Chief Signal-Officer" for 1884, which maps were compiled at the suggestion and earnest solicitation of the Colorado State Medical Society.

They show plainly that, in the spring and autumn of 1882, the portion of the United States which contained the fewest grains of vapor to the cubic foot of air (viz., 1·5 grain) was the portion of the Rocky Mountain range reaching from near the northern boundary of Wyoming to about the center of New Mexico and Arizona; and that, while during the winter months the Northwest, owing to the extreme cold, contained only from 0·5 to 1·0 grain of vapor, that section which we are considering contained the same amount throughout its northern half, while its southern half ranged from 1 to 1·5 grain. During the same winter months the vapor along the California coast is marked as having been 2·5 grains to the foot, and in Florida it was 4 grains in the north and 7 grains at Key West.

We wish to emphasize this matter of extreme atmospheric dryness, as it not only plays a most important part in a consideration of the climatic cure of consumption, but it is also a prime factor in making, what to an Eastern mind may appear as low temperatures, not only bearable but even comfortable.

Says Professor Frankland, "The absence of suspended watery particles in the air has, no doubt, very considerable influence in preventing the chilling of the skin"; and this, together with diminished atmospheric pressure—which, the same writer says, makes the air, if still, feel warmer at an elevated station than in lower and denser regions of the atmosphere, "in consequence of the slower abstraction of heat from the body"—these conditions, we say, are the reasons why low temperatures with us do not feel so cold—and, so far as being out of doors is concerned, really are not so cold—as the corresponding temperatures at sea-level.

The next favorable atmospheric condition mentioned as existing at Davos is the fact that there is a "clear sun," by which, we presume, is meant an absence of clouds and a large amount of sunshine.

In this connection we have previously called attention to the fact that there are in this climate, on the average, three hundred and twenty sunny days per annum, when the invalid can be out of doors. In other words, our cloudy days, as interpreted by the Signal Service—i. e., days when the heavens are from seven tenths to ten tenths obscured by clouds at 7, 3 and 11 , Washington time—our cloudy days average only forty-six, while in New York they average one hundred and nine, at Jacksonville eighty-seven, and at St. Paul one hundred and four per annum.

This fact also has been graphically portrayed by another series of