Separating this valley from the Pacific is a succession of ranges trending parallel with the coast and known as the Coast ranges. In southern California the valleys among these ranges are of the highest degree of fertility and produce grapes and tropical fruits in profusion. Farther north the country is but little settled or even explored.

DISTRIBUTION OF POPULATION WITH REFerence to MEAN ANNUAL RAINFALL.

In 1890 Mr. Gannett obtained (from reports furnished chiefly through the Weather Bureau from nearly 2,000 stations) data from which he platted upon a map of the United States the curves of mean annual rainfall, at intervals of ten inches, sketched in accordance with their indications, and supplemented by his knowledge of the relief of the country and its known influence upon rainfall. From the map thus prepared the counties falling between the different curves of mean annual rainfall were drawn off in lists. In cases where the county was cut in parts by a curve, due weight was given in the partition of the county to any inequality in distribution of population. The population was then distributed by counties in accordance with the lists. The result is shown in the table below.

In this table the first column shows the grades, expressed in inches of rainfall; the second, third, and fourth columns, the number of inhabitants found in each grade in 1890, 1880, and 1870, assuming that the total population at each of the above periods was one hundred thousand, or, in other words, the percentage of the population in each of these grades at the periods under consideration, carrying the figures out to the thousandth of 1 per cent; the fifth and sixth columns show the increase or decrease in number; the seventh, eighth, and ninth columns show the number of inhabitants in each one hundred thousand above each grade, and therefore are cumulative columns; the tenth, eleventh, and twelfth columns show the density of population in each grade in 1890, 1880, and 1870, and the last two columns show the increase in population per square mile.

It will be noticed that the main body of the population of the country inhabits the region in which the annual rainfall is between 30 and 50 inches, three-fourths of the inhabitants or thereabouts being found there. On either side, as the rainfall increases or diminishes, the population diminishes rapidly. It will be seen further that the arid region of the west, where the rainfall is less than 20 inches-a region which comprises two-fifths of the entire area of the country-contains at present less than 3 per cent of the population.

The greatest density of population is in the area enjoying from 40 to 50 inches of annual rainfall, the average of this region being 59 inhabitants to the square mile. Next to that is the area having from 30 to 40 inches, where the density is 43.1. The density of population has increased rapidly in these regions. It is apparent, however, that the most rapid increase, as expressed by density of population, is where the rainfall ranges from 20 to 30 inches; that is in the eastern portion of the Great Plains ranging from Texas to the Dakotas, where the density has increased in twenty years from 1.6 to 8.1.

The average annual rainfall upon the surface of the United States, as deduced from the map previously mentioned, is 29.6 inches. The average annual rainfall with relation to the population, deduced by giving weight to each area of country in proportion to the number of its inhabitants, was, in 1870, 42.5 inches; in 1880 it had diminished to 42 inches, and in 1890 to 41.4 inches, the diminution being caused mainly by the settlement of the Great Plains and the arid regions of the west. DISTRIBUTION OF POPULATION IN ACCORDANCE WITH

MEAN RELATIVE HUMIDITY OF ATMOSPHERE. On the coast of Oregon and Washington, the atmosphere is more highly charged with moisture than elsewhere within our territory. The high mountain regions of the Appalachian and to a considerable extent those of the Rocky mountain ranges also have a moist atmosphere. The moisture is less in the Piedmont region east of the Appalachians and in the upper Mississippi valley. Passing across the prairie and the great plains, the amount of moisture in the atmosphere diminishes still more, while the minimum is reached in the Great Basin, in Utah, Nevada, southern Arizona, and southeastern California. In a general way, the amount of moisture in the atmosphere increases and decreases with the rainfall, but this is not always the case. The upper lake region, with an atmosphere as moist as that of Washington city, has a much smaller rainfall. The coast of

Southern California, with a deficient rainfall, has as moist an atmosphere as the Atlantic coast.

In the following table the first column defines the classes of population grouped by percentages of saturation of the atmosphere in the sections in which the people reside; the second gives the number of inhabitants in each class expressed in round thousands; the third, the percentage of increase during the last decade; the fourth, the percentage of total population; the fifth, the density of population, or the population per square mile in each class.

nett, Geographer and Special Agent of the Census Department.

Naturally the greater density of population in a square degree is governed by the location of the larger cities. Thus the two square degrees between latitudes 40 and 41° and longitudes 73° and 75°, comprising New York, Brooklyn, Jersey City, and other large cities, contain 3,653,000 inhabitants. The square degree between latitudes 420 and 430 and longitudes 710 and 720, comprising Boston and its suburbs, has 1,233,000 inhabitants;

A glance at this table shows that nearly all the population breathe an atmosphere containing 65 to 75 per cent. of its full capacity of moisture; that is, the atmosphere is from two-thirds to threefourths saturated. In 1890, 57,036,000 out of 62,622,250 were found in this region. The number of inhabitants living in a drier atmosphere was at the date of the census comparatively trifling, numbering in 1890 less than two millions. In the moister atmosphere were found larger numbers scattered along the Gulf coast and the shores of Washington and Oregon.

DISTRIBUTION OF POPULATION IN RESPECT OF LATITUDE AND LONGITUDE.

The following diagrams show the distribution of population of the United States with respect of latitude and longitude at the dates severally of the last three censuses. They were prepared for the report of the census of 1890 by Henry Gan

32,148

38,119

1.2

225,049

208,643

0.9

Klamath river.

Columbia river.

Willamette river.

Census Years.

Population of the United States.

The areas of the respective drainage basins were determined with care, and adjusted to suit the total area of the United States, exclusive of Alaska.

URBAN POPULATION OF THE UNITED STATES.

In the census reports of the United States the urban population has been understood as that included in cities which have each 8,000 inhabitants and over. While this limit is now recognized as too high (the 4,000 limit being generally regarded as the better one), it has been continued for the convenience of comparisons with the figures of the previous census reports.

The urban population returned in 1890 is 29.12 per cent. of the total population of the whole country. The following are the corresponding figures for the several censuses:

population.

It will be seen that the proportion of urban population has increased gradually during the past century from 3.35 up to 29.12 per cent. or from onethirtieth up to nearly one-third of the total population. The increase had been quite regular from the beginning up to 1880, while from 1880 to 1890 it made a leap from 22.57 up to 29.12 per cent. thus illustrating in a forcible manner the accelerated tendency of our population toward urban life. The number of cities having each a population of more than 8,000 increased from 6 in 1790 to 286 in 1880, whence it leaped to 443 in 1890.

In 1870 there were only 14 cities reporting each a population of 100,000 or over; in 1880 there were 20; and in 1890 the number had increased to 28. In 1880 New York was the only city whose population had reached a million; now there are three, namely: New York, Chicago, and Philadelphia. The list and relative rank of the cities having each a population of 100,000 in the census years of 1870, 1880, and 1890 are shown as follows: