THE DARLING PENEPLAIN OF WESTERN AUSTRALIA. 387 
on a land surface of low altitude has not been insisted on 
previously. 
If this view is correct it follows that the original laterite 
formation of Western Australia may be taken as an indica- 
tion of the peneplain surface. The question is suggested, 
why are not all peneplains indicated by laterite cappings ? 
The answer is that several conditions, other than ordinary 
{and therefore in general partial) peneplanation, are neces- 
sary. So long as normal and effective drainage exists, the 
ferruginous and aluminous solutions are largely carried 
away seawards. It is only when practical stagnation is 
attained, that is, when the peneplain stands for long ages 
at base level, that the necessary concentration of solutions 
takes place. In the second place the alternation of seasona! 
desiccation and saturation is also necessary. This coincid- 
ence of circumstances is rarely attained. .This view of the 
case bears out Jutson’s main contention with regard to the 
origin of the Western Australian Uplands. To the South 
Western section of these Uplands he applies the term 
Darling Peneplain, and it is to this portion of the area that 
the author wishes to draw attention chiefly. Thealtitude 
of the laterite ‘“‘level’’ rises gradually from about 800 feet 
above sea level at the Darling Scarp overlooking the coastal 
plains, to 1,400 feet’ at Coolgardie, and 1,700 feet at 
Meekatharra. 
The surface of the Darling Range is remarkably level 
(neglecting the obviously recently-denuded valleys of the 
existing streams) and the skyline is very even. When 
examined in closer detail, however, quite considerable 
differences in altitude of different parts of the laterite cap 
. are noticeable. These are, in part, and probably principally, 
due to the sagging of the outer edges of ‘‘Mesa”’ cappings 
through the removal of the very decomposed granitic 
material on which the laterite universally rests. 
