38 LEOPOLD REINECKE 



near the ocean at the time of their formation. If the geographic 

 unit be large, parts of it must lie far from the ocean and may be at 

 a considerable elevation above it. 1 The "Almost plains" are char- 

 acterized as presenting absolute discordance between topography 

 and structure, graded streams and hill slopes, that is, practically 

 a lack of cliff and local flat surfaces, and by deep soil covering. 

 These are the commonly accepted criteria for determining pene- 

 planation. In addition, we suggest that the term be restricted 

 to surfaces with average slopes of less than 2 per cent, 105 feet to 

 the mile. For examples of peneplains one may cite the Laurentian 

 peneplain 2 of Canada, and a peneplain in the Mississippi Valley 

 illustrated by the Caldwell, Kansas, topographic map sheet. 3 

 The Laurentian peneplain has an area of about two million square 

 miles, with average slopes of about one-tenth of 1 per cent. It 

 differs from an ideal type in that it has been modified by the 

 accident of glaciation in removing the residual soil, in substituting 

 an irregular drift mantle, and in slightly altering the form of the 

 original surface. Upon the Caldwell area, average slopes vary from 

 10 to 50 feet to the mile, that is from one-fifth of 1 per cent to 

 1 per cent. 



"Beveled hills'' are characterized as geographic units worn 

 down to moderate relief by subaerial processes alone. Their 

 "essential" characters are discordance of topography and structure, 

 graded slopes, smooth sky lines and contours, and a deep soil cover- 

 ing. Their "accessory" characters are local accordance between 

 topography and structure, and the local occurrence of cliff faces 

 and flat areas, that is, of ungraded slopes. In this instance the 

 terms "essential" and "accessory" are used in the same way as 

 they are in petrography, essential characters being those which 

 predominate within the land form, accessory those of which but 

 few examples can be found and which may be entirely absent. 



"Peneplains" and "beveled hills" are distinguished therefore 

 by their degree of slope and also by the occasional finding in the 



1 W. M. Davis, "The Colorado Front Range," Ann. Assoc. Am. Geog., I, 42. 



2 A. W. G. Wilson, "The Laurentian Peneplain," Jour. Geol., XI (1903), 628-29. 

 ^ Henry Gannett, "Topographic Atlas of the United States. Physiographic 



Types," U.S.G.S., Folio 1, Caldwell, Kansas, sheet, 189S. 



