Page:Popular Science Monthly Volume 40.djvu/392

376 in accordance with mean relative humidity becomes apparent, and the Census Office is doing a great service in this census, as it did in 1880, in ascertaining the density of population under different degrees of humidity. A condensation of the report by Mr. Gannett on this point will perhaps give as much valuable information to those seeking healthful locations as can be gained from any side of census statistics. It is well known that the atmosphere is heavily charged with moisture in those regions which lie along our coast, whether ocean, gulf, or lake. This is markedly so on the coast of Oregon and Washington, where the atmosphere is more highly charged with moisture than anywhere else within our territory. The Appalachian Mountain regions, and largely those of the Rocky Mountains, have an atmosphere heavily charged; but in the Piedmont region, east of the Appalachian, and in the upper Mississippi Valley, the moisture is less, while it diminishes still more on the prairies and the Great Plains; and in Utah, Nevada, southern Arizona, and southeastern California the minimum amount is reached. Of course the atmosphere is charged with moisture relative to the increase and decrease of the rainfall, as a rule; but throughout the upper lake region, while the atmosphere is as moist as that of the State of Washington, the rainfall is much less, and the coast of southern California has as moist an atmosphere as the Atlantic coast but a deficient rainfall.

The following table shows the percentage of humidity, in classified order, the percentage of the total population of the United States in 1870, 1880, and 1890, living according to the classification of humidity, and the density of population under the same conditions for the same years:

A glance at this table shows that nearly all the population breathe an atmosphere containing sixty-five to seventy-five per cent of its full capacity of moisture; that is, the atmosphere is from two thirds to three fourths saturated. In 1890, 57,036,000 out of 62,622,250 were found in this region; in 1880, 46,559,000 out of 50,155,783; and in 1870, 36,273,000 out of 38,558,371. The