PAPERS OF GExNERAL INTEREST 37 



But mere altitude above sea level is, however, often mis- 

 leading and gives little idea of either the appearance or the 

 importance of a highland. 



While it is true that the mounds of Jo Davies county do 

 have an elevation almost 200 feet higher than the highest 

 hill of the Ozarks, still the reader must keep in mind that 

 the general level of Illinois in Jo Davies county is twice as 

 great as that in the region of the Ozarks. For instance, the 

 highest hills in Jo Davies county are only from 200 to 250 

 feet above the general level of that part of Illinois,"- while 

 the highest hills in the Ozarks are from 500 to 600 feet 

 above the general level in the southern section of the state. 

 The northern base of the Ozarks at Carbondale, for example, 

 is only 415 feet above sea level, and the southern base of the 

 Ozarks is but little over 300 feet. 



It is this difference in altitude between the general level 

 of its surroundings and the tops of the higher hills in the 

 crest of the Ozarks, rather than mere height above sea level, 

 that makes the Ozarks the most conspicuous highland in 

 Illinois. This difference of 500 to 600 feet between crest 

 and base of the Ozarks gives its streams sufficient power to 

 carve this region into a complex of deep valleys and ravines 

 alternating with high narrow^ crested ridges or steep sided, 

 irregularly shaped hills. 



As a whole the Ozarks are in the mature stage of the cycle 

 of erosion; but there are several sections that should not 

 be classed any later than late youth. East of Makanda, in 

 Jackson county, there is a region of considerable size, that 

 has a number of farms on the summit of the Ozarks that are 

 comparatively level. Near the village of Ozark, in Johnson 

 county, there is another region of fiat topped hills where the 

 land is comparatively level over a considerable area. There 

 are, no doubt, other regions with similar surface features 

 which can not be regarded as maturely dissected. 



It is thus seen that the surface of this upland is by no 

 means alike over the entire highland. The chief reasons 

 for these differences of surface are: First, the amount, 



2. Ridgeway: Natural Hist, of 111., Vol. I, pp. 7. 



