Page:Popular Science Monthly Volume 28.djvu/689

Rh highly esteemed by the advocates of elevated and cool resorts, we find in Colorado that, so far as elevation is concerned, the range in the towns is from that of Denver, at 5,280 feet, to that of Leadville, which is somewhat over 10,000 feet above sea-level. Intermediate are Colorado Springs, 6,000 feet; Manitou Springs, between 6,000 and 7,000 feet; Cañon City, about the same; Salida, 7,000 feet; Poncha Springs, Idaho Springs, Boulder, and Longmont, about 7,500 feet; Gunnison, Georgetown, and Alamosa, in the neighborhood of 8,000 feet, and so on. So that all the arguments derived from elevation above sea-level are applicable to Colorado as well as to Davos.

If at Davos it is found that there is diminished atmospheric pressure; that, as a consequence, there is a slower abstraction of heat from the body, so that low temperatures do not feel so cold as they would in a lower and denser region; that there is greater heating power in the direct rays of the sun, and that there is a freedom from germ-life (a supposition based on the experiments of Pasteur and Tyndall), all due to simple elevation, the same has been found to be true in Colorado.

As regards the humidity of the air, on which condition writers on climate lay so much stress, and among them the author to whom we have already referred, the data are full and satisfactory.

Colorado is situated in the zone of greatest atmospheric dryness, both relative and absolute, of any inhabited portion of the United States.

A compilation of the statistics of the Signal-Service Bureau, United States Army, shows that the mean relative humidity of Denver for four years was only 45·8. That is, taking the saturation-point, or the point at which the atmosphere is holding all the moisture that it can, as 100, then the air at Denver is only 45·8 per cent of saturation, and it is capable of holding 54·2 per cent more moisture than it does. The same table shows that the air of New York is 70·2 per cent of saturation; that of Jacksonville, Florida, 69 per cent, and that of Los Angeles 65·8 per cent.

It must be understood, in this connection, that the saturation-point is not at all a fixed one, nor is it a constant quantity at any given place, as it varies both with the barometric pressure and with the temperature; so that, as a consequence of this, many writers prefer to speak of the absolute rather than of the relative humidity, in making comparisons of the atmospheric dryness of places.

Several years ago we had occasion to point out, in this connection, that, while a mean for four years showed that the Denver air contained only 1·81 grain of vapor (by weight) to the cubic foot, the air of Jacksonville contains 5·38 grains, and that of Los Angeles 3·77 grains, to the foot; or, as we then remarked, an "amount which, as between Denver and Jacksonville, is as 1 to 3, and, as between Denver and Los Angeles, is as 1 to 2."