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THE POPULAR SCIENCE MONTHLY. 



lation in accordance with mean relative humidity becomes appar- 

 ent, 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 Appa- 

 lachian, 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 Cali- 

 fornia the minimum amount is reached. Of course the atmos- 

 phere 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 num- 



