PHYSIOGRAPHY OF THE BEAVERDELL MAP-AREA, 
3 
gressed in the geographic cycle, the greatest stress was laid upon 
regional slopes within the upland. Other criteria were used in 
a supplementary way but were not given as much weight. 
The measurements of slopes and detailed study over all the 
upland in the Beaverdell area gave an opportunity for testing the 
value of certain criteria commonly used in determining the stage 
to which a land form had progressed in the geographic cycle. 
Characteristic forms commonly used as criteria of the peneplana- 
tion of a land surface were found developed in places on the 
Beaverdell upland, a surface with regional slopes of from 100 to 
300 feet per mile. By depending on these criteria, therefore, and 
neglecting the regional slopes, one would class a surface with 
that degree of slope with existing peneplain surfaces on which 
the slope is not over 10 feet to the mile. The danger of the ap- 
plication of such criteria to isolated remnants of an old surface, 
in cases where there are no means of measuring the average 
regional slopes, lies in the fact that these remnants are in some 
cases assumed to be the remains of a land form at one time nearly 
flat and, on that assumption, are used to measure earth warping 
by. The criterion of regional slopes is, therefore, suggested 
as a quantitative method for subdividing old land forms. 
This investigation has shown that the uplands have the same 
topographical forms over the southern part of the Interior 
plateaus and that their physiographic development has been 
along the same lines; that there are no true peneplain remnants 
in them and that the present upland surface is that of late matur- 
ity. The development of the deep valleys and the terraces on 
their bottoms, as well as the effects of glaciation, are also dis- 
cussed, but are of minor interest. 
Arrangement. 
This bulletin consists of four parts exclusive of the intro- 
ductory section. The first contains a short description of the 
Canadian Cordillera and the second a more extended description 
of the Interior plateaus. In the third the topography of the 
Beaverdell map-area is described in detail. It begins with a 
summary description of the area, and in reading this section the 
