_Physiography._--Topographically, Indiana is similar to Ohio and Illinois, the greater part of its surface being undulating prairie land, with a range of sand-hills in the N. and a chain of picturesque and rocky hills, known as "Knobs," some of which rise to a height of 500 ft., in the southern counties along the Ohio river. This southern border of hills is the edge of the "Cumberland Plateau" physiographic province. In the northern portion of the state there are a number of lakes, of glacial origin, of which the largest are English Lake in Stark county, James Lake and Crooked Lake in Steuben county, Turkey Lake and Tippecanoe Lake in Kosciusko county and Lake Maxinkuckee in Marshall county. In the limestone region of the south there are numerous caves, the most notable being Wyandotte Cave in Crawford county, next to Mammoth Cave the largest in the United States. In the southern and south-central part of the state, particularly in Orange county, there are many mineral springs, of which the best known are those at French Lick and West Baden. The larger streams flow in a general south-westerly direction, and the greater part of the state is drained into the Ohio through the Wabash river and its tributaries. The Wabash, which has a total length of more than 500 m., has its headwaters in the western part of Ohio, and flows in a north-west, south-west, and south direction across the state, emptying into the Ohio river and forming for a considerable distance the boundary between Indiana and Illinois. It is navigable for river steamboats at high water for about 350 m. of its course. Its principal tributaries are the Salamanie, Mississinewa, Wild Cat, Tippecanoe and White rivers. Of these the White river is by far the most important, being second only to the Wabash itself in extent of territory drained. It is formed by the confluence of its East and West Forks, almost 50 m. above its entrance into the Wabash, which it joins about 100 m. above the Ohio. Other portions of the state are drained by the Kankakee, a tributary of the Illinois, the St Joseph and its principal branch, the Elkhart, which flow north through the south-west corner of Michigan and empty into Lake Michigan; the St Mary's and another St Joseph, whose confluence forms the Maumee, which empties into Lake Erie; and the White Water, which drains a considerable portion of the south-west part of the state into the Ohio.