44 LEOPOLD REINECKE 



not detract from the usefulness of the quantitative definition of the 

 family, but rather adds to the necessity of such a definition. In 

 the same way the term "beveled hills" proposed here represents 

 a land form which actually occurs over the known portion of a large 

 geographic unit, the Interior Plateaus of British Columbia, and the 

 quantitative limits proposed for the type are those measured upon 

 the land form in question. The value of the establishment of a 

 subdivision centering about a quantitatively defined physiographic 

 type should also not be seriously impaired by the occurrence of 

 numerous intermediate forms. 



b) The slopes on a land form vary widely, and an accurate 

 average is not easily obtained. Variation in slope will cause 

 trouble only in old surfaces of fairly high relief, that is, in the 

 "beveled hills" type. In the work in the Interior Plateaus, it was 

 found that the greater part of the surface within areas of about 

 200 square miles lay between 3 and 6 per cent, and where slopes of 

 a mile or more in length varied greatly from the general average 

 they occurred over small areas. By estimating the relation of the 

 size of these areas to the whole, irregularities of slope were cal- 

 culated into the whole, and found to change the general average 

 very slightly. If care is taken first carefully to separate forms due 

 to different cycles, and then to note the frequency of the occurrence 

 of irregularities varying from the average, the final results will be 

 found to be fairly consistent. 



In land of lower relief, that is, in the peneplain division, the 

 results will be found to agree much more closely for the variation 

 in slope is very much less. 



c) The amount of field work is greater than is necessary when 

 slopes are not measured. 



This is true even when the measurements are made on topo- 

 graphic maps, for in order to appreciate the meaning of the forms 

 shown on a topographic map it is necessary that one examine them 

 closely at first hand. The extra time and energy which physi- 

 ographers will of necessity have to spend in traversing old land 

 surfaces before they can obtain data upon the nature and extent 

 of their slopes is one of the best arguments for the adoption of this 

 classification instead of an objection to it. The geologist knows 



