64 
indicate a very advanced stage of erosion of what doubtless were 
once much higher and more important hills. Very little more and 
the hills would he cut down entirely to one great peneplain. This 
form of level surface characteristically results from long-continued 
sub-aerial erosion, and its occurrence is therefore to some extent 
prima facie evidence tliat the land has been for a very long time 
subjected to the subaerial agencies which would bring about such 
features. It may fairly be submitted, however, that if a land 
surface in such or afiproaching such a mature stage of ]danation 
were to subside below sea-level to such an extent as to bring the 
sea over the greater i)art of it. and were again to be elevated well 
above the sea level, the effects of the original merely subaerial 
planation would be greatly accentuated by marine erosion during 
the periods in which the surface was in process of being submerged 
and raised again. 
While the low hummocky type of hills surrounded by plains 
is characteristic of the lower ground, there is a very marked 
change in the type of land scul])ture when we get into some of the 
higher country. One of the best examples seen in the Frazer 
Range to the west of Rcak Hill. Here wo suddenly find ourselves 
in the t)resence of a hill-sculpture of a type quite unlike the hills 
previously described. Instead of low rounded hills there are 
rough ragged peaks with their sides deeply fui rowed into hard 
sharp-edged outstanding ridges and deep rough ravines, and giving 
jagged pointed outlines from all aspects, d'he type is that of an 
outstanding rock-mas.s deeply <lissected by storm-water erosion. 
I'kit at the foot of it, at the Mount Fraser mine, the a])proach is 
over wonderfully level plains running against the hills exactly as 
one sees sea-beaches form against a rugged hilly shore. A short 
distance out on the plain a well has been sunk to a depth ot ab'rat 
140 feet, passing through alluvial material containing much small 
gravel, fairly rounded, of river type, showing that the flat has a 
buried valley in it. The existing flat carries one of the numerous 
branches of the Murchison River, seen as a running stream only 
after heavy rains. Between the well ami the Mount Fraser mine 
the track jiasses over one of the most striking geological curiosities 
it has been the writer’s fortune to observe. The bedrock is a 
hard jirismatically jointed greenstone, the surface of which is 
often quite bare of soil for yards at a time. In one or two places 
noticed, the bare rock surface was seen to be cut to a quite even 
plane, forming a smooth floor to which the joints gave the ajiiiear- 
ance of a mosaic pavement, the prismatic columns being there 
rarely as much as an inch across. It is difficult to believe that 
wind could have ])laned such a hard rock to an even surface, 
though the occurrence is quite com])rehensible if regarded as 
formed by l)each erosion. .\t this place also the resemblance of 
the edge of the ]jlain to a beach is most marked; it is quite level 
and runs in and out among the rocky spurs meeting it in the most 
