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 most common, the rate of illegitimacy is high, and that it is low in the more illiterate parts, e.g. Ireland and Brittany.

It has been said that one of the contributory causes of illegitimacy is the contamination of great cities; statistics, however, disprove this, there being more illegitimacy in the rural districts. Table VII. gives the rate of illegitimacy in some of the principal towns of the United Kingdom.

That poverty is a determining factor in causing illegitimacy the following figures, giving the rate of illegitimacy in the poorest parts of London and in certain well-to-do parts, clearly disprove:—

Rate of Illegitimacy per 1000 Births.

Tables VIII. and IX. give the rate of illegitimacy for the various counties of Scotland, and Table X. the rate for Ireland.

—The Annual Reports of the Registrars-General for England, Scotland and Ireland; statistical returns of foreign countries; A. Leffingwell, Illegitimacy and the Influence of the Seasons upon Conduct (1892).

 ILLER, a river of Bavaria, rising in the south-west extremity of the kingdom, among the Algäuer Alps. Taking a northerly course, it quits the mountains at Immenstadt, and, flowing by Kempten, from which point it is navigable for rafts, forms for some distance the boundary between Bavaria and Württemberg, and eventually strikes the Danube (right bank) just above Ulm. Its total length is 103 m.  ILLINOIS, a North Central state of the United States of America, situated between 37° and 42° 30′ N. lat. and 87° 35′ and 91° 40′ W. long. It is bounded N. by Wisconsin, E. by Lake Michigan and Indiana, S.E. and S. by the Ohio river, which separates it from Kentucky, and S.W. and W. by the Mississippi river, which separates it from Missouri and Iowa. The Enabling Act of Congress, which provided for the organization of Illinois Territory into a state, extended its jurisdiction to the middle of Lake Michigan and the Mississippi river; consequently the total area of the state is 58,329 sq. m., of which 2337 sq. m. are water surface, though the official figures of the United States Geological Survey, which does not take into account this extension of jurisdiction, are 56,665 sq. m.

Physiography.—Physiographically, the state (except the extreme southern point) lies wholly in the Prairie Plains region. The N.E. corner is by some placed in the “Great Lakes District.” The southern point touches the Coastal Plain Belt at its northward extension called the “Mississippi Embayment.” The surface of Illinois is an inclined plane, whose general slope is toward the S. and S.W. The average elevation above sea-level is about 600 ft.; the highest elevation is Charles Mound (1257 ft.), on the Illinois-Wisconsin boundary line, one of a chain of hills that crosses Jo Daviess, Stephenson, Winnebago, Boone and McHenry counties. An elevation from 6 to 10 m. wide crosses the southern part of the state from Grand Tower, in Jackson county, on the Mississippi to Shawneetown, in Gallatin county, on the Ohio, the highest point being 1047 ft. above the sea; from Grand Tower N. along the Mississippi to the mouth of the Illinois there is a slight elevation and there is another elevation of minor importance along the Wabash. Many of the river bluffs rise to an unusual height, Starved Rock, near Ottawa, in La Salle county, being 150 ft. above the bed of the Illinois river. Cave in Rock, on the Ohio, in Hardin county, was once the resort of river pirates. The country S. of the elevation (mentioned above) between Grand Tower and Shawneetown was originally covered with forests.

The drainage of Illinois is far better than its low elevation and comparatively level surface would suggest. There are more than 275 streams in the state, grouped in two river systems, one having the Mississippi, which receives three-fourths of the waters of Illinois, as outlet, the other being tributary to the Wabash or Ohio rivers. The most important river is the Illinois, which, formed by the junction of the Des Plaines and the Kankakee, in the N.E. part of Grundy county, crosses the N. central and W. portions of the state, draining 24,726 sq. m. At some points, notably at Lake Peoria, it broadens into vast expanses resembling lakes. The Kaskaskia, in the S., notable for its variations in volume, and the Rock, in the N., are the other important rivers emptying into the Mississippi; the Embarrass and Little Wabash, the Saline and Cache in the E., are the important tributaries of the Wabash and Ohio rivers. The Chicago river, a short stream 1 m. long, formed by the union of its N. and S. branches, naturally flowed into Lake Michigan, but by the construction of the Chicago Drainage Canal its waters were turned in 1900 so that they ultimately flow into the Mississippi.

The soil of Illinois is remarkable for its fertility. The surface soils are composed of drift deposits, varying from 10 to 200 ft. in depth; they are often overlaid with a black loam 10 to 15 in. deep, and in a large portion of the state there is a subsoil of yellow clay. The soil of the prairies is darker and coarser than that of the forests, but all differences disappear with cultivation. The soil of the river valleys is alluvial and especially fertile, the “American Bottom,” extending along the Mississippi from Alton to Chester, having been in cultivation for more than 150 years. Along the river bluffs there is a silicious deposit called loess, which is well suited to the cultivation of fruits and vegetables. In general the N. part of the state is especially suited to the cultivation of hay, the N. and central parts to Indian corn, the E. to oats, and the S.W. to wheat.

Climate.—The climate of Illinois is notable for its extremes of temperature. The warm winds which sweep up the Mississippi Valley from the Gulf of Mexico are responsible for the extremes of heat, and the Arctic winds of the north, which find no mountain range to break their strength, cause the extremes of cold. The mean annual temperature at Winnebago, near the N. border, is 47° F., and it increases to the southward at the rate of about 2° for every degree of latitude, being 52° F. at Springfield, and 58° F. in Cairo, at the S. extremity. The lowest temperature ever recorded in the state was &minus;32° F., in February 1905, at Ashton in the N.W. and the highest was 115° F., in July 1901, at Centralia, in the S., making a maximum range of 147° F. The range of extremes is considerably greater in the N. than in the S.; for example, at Winnebago extremes have ranged from &minus;26° F. to 110° F. or 136° F., but at Cairo they have ranged only from &minus;16° F. to 106° F. or 122° F. The mean annual precipitation is about 39 in. in the S. counties, but this decreases to the northward, being about 36 in. in the central counties and 34 in. along the N. border. The mean annual snowfall increases from 12 in. at the S. extremity to approximately 40 in. in the N. counties. In the N. the precipitation is 44.8% greater in spring and summer than it is in autumn and winter, but in the S. only 26.17% greater. At Cairo the prevailing winds are southerly during all months except February, and as far north as Springfield they are southerly from April to January; but throughout the N. half of the state, except along the shore of Lake Michigan, where they vary from N.E. to S.W., the winds are mostly from the W. or N.W. from October to March and very variable for the remainder of the year. The dampness and miasma, to which so many of the early settlers’ fatal “chills and fever” were due, have practically disappeared before modern methods of sanitary drainage.

Fauna and Flora.—The fauna and flora, which are similar to those of the other North Central States of North America, impressed the early explorers with their richness and variety. “We have seen nothing like this for the fertility of the land, its prairies, woods, and wild cattle,” wrote Père Jacques Marquette of the Illinois region, and later explorers also bore witness to the richness of the country. Many of the original wild animals, such as the bison, bear, beaver, deer and lynx, have disappeared; wolves, foxes and mink are rare; but rabbits, squirrels and raccoons are still common. The fish are mainly the coarser species, such as carp, buffalo-fish and white perch; of better food fish, the principal varieties are bass (black, striped and rock), crappie, pike, “jack salmon” or wall-eyed pike, and sun fish. The yield of the fisheries in 1900 was valued at $388,876. The most important fisheries on the Illinois river and its tributaries were at Havana, Pekin and Peoria, which in 1907–1908 were represented by a total catch of about 10,000,000 ℔, out of a total for this river system of 17,570,000 ℔. The flora is varied. Great numbers of grasses and flowering plants which once beautified the prairie landscape are still found on uncultivated lands, and there are about 80 species of trees, of which the oak, hickory, maple and ash are the most common. The cypress is found only in the S. and the tamarack only in the N. The forest area, estimated at 10,200 sq. m. in 1900, is almost wholly in the southern counties, and nearly all the trees which the northern half of the state had before the coming of the whites were along the banks of streams. Among wild fruits are the cherry, plum, grape, strawberry, blackberry and raspberry.

Industry and Commerce.—The fertility of the soil, the mineral wealth and the transportation facilities have given Illinois a vast economic development. In 1900 more than seven-tenths of the inhabitants in gainful occupations were engaged in agriculture (25.6%), manufactures and mechanical pursuits (26.7%), and trade and transportation (22%). 