remaining, situated principally in the Iron Mountain district in northeastern Missouri, rise from 1,400 to 1,800 feet above the neighbouring plains, and from 1,800 to 2,100 feet above the sea. The greater intensity with which the rocks in the southwestern portion of the Ozark uplift have been folded than in the more northern portion and the varying degrees to which the beds have yielded to denudation have resulted in giving to its various parts different types of topography. This diversity has led to the recognition of several distinct divisions, such as the Shawnee Hills, at the extreme northeastern end of the uplift, where the rocks have been folded and the ridges cut across by the Mississippi; the St. Francois Mountains, in southeastern Missouri, composed of a large number of isolated hills and rising from 500 to 800 feet above the adjacent valleys; the Ozark plateau, in southwestern Missouri and northwestern Arkansas, the central part of which has a general elevation of 1,500 feet above the sea, and to one travelling over it seems a boundless and featureless plain underlaid by apparently horizontal but in reality gently westward dipping sheets of stratified rocks; the Boston Mountains, in central and western Arkansas, consisting of rugged irregular ridges and truncated summits with a general crest-line elevation of 1,000 feet above the sea; and the Ouachita (pronounced _Wichitaw_) Mountains, formed of numerous rudely parallel upward folds of hard rock, which rise from 500 to 1,000 feet above the adjacent valleys and form a belt of unusually picturesque, forest-crowned hills, extending from Little Rock, Arkansas, westward into Indian Territory.