Walker's Statistical Atlas of the United States. 87 
tion of a region more sparsely inhabited than that are scarcely 
permanent enough to be called settlers. He traces the line sur- 
rounding such areas, and also of each of the adopted degrees 
of density. The following table gives some of the more sim- 
ple features of this calculation. 
Total area of Average density of 
Date. settlement, Population. settlement. Persons 
in square miles. to i 
1790 239,935 3,929,214 16°4 
1800 305,708 5,308,483 17°3 
1810 407,945 7,239,881 17°7 
1820 508,717 9,633,822 18°9 
1830 632,717 12,866,020 20°3 
1840 807,292 17,069,453 Zt 
1850 979,249 23,191,876 23°7 
1860 1,194,754 31,443,521 26°5 
1870 1,272,239 38,558,371 30°2 
It is noticed here that in the 40 years following 1790, the 
area of settlements increased 168 per cent, and the density 24 
per cent, while in the next 40 years the area increased 101 
per cent and the density 44 per cent. While this increased 
ratio of density is in part due to the denser settlement of rura 
districts, it is mostly due to an increase in the city and village 
populations. We find that in 1800 there were but six cities of 
over 8,000 inhabitants, and in 1840 but 44; the number had 
icreased to 226 in 1870. He says: “Speaking roundly, it 
may be said that in 1790 one-thirtieth of the population was 
found in cities; in 1800 one twenty-fifth; in 1810 and also in 
1820 one-twentieth ; in 1830 one-sixteenth ; in 1840 one-twelfth ; 
prise one-eighth ; in 1860 one-sixth; in 1870 more than one- 
That popular subject of so many writers, “the center of 
population,” is also fully discussed. In 1790 it was “about 23 
mules east of Baltimore.” It has traveled westward, keeping 
curiously near the 39th degree of latitude, never getting more 
than 20 miles north nor two miles south of it. In the 80 years 
it has traveled only 400 miles and is still found nearly 50 miles 
eastward of Cincinnati. : 
The intimate and varied relations between the density and 
spread of population as shown by the maps of the second part, 
and the physical features of the country as shown by the maps 
of the first part, are intensely interesting and varied, but the 
subject is too fertile to be entered on here. 
Part 3d consists of two memoirs and eighteen plates, six of 
which are maps. They may be said to cover three classes of © 
. 
subjects, one relating to age, sex and birth, the next to mortal- 
ity, the third to the “ afflicted classes.” The relative distribution 
