66 
^Marble Bar and Lalla Rookh stands out like a rugged island from 
the smoothly-worn plains surrounding it, and the edges of the 
plains lying against the high land all round maintain a strong- 
general likeness to beaches. d'he hills themselves are peaked, 
furrowed, and jagged, the peaks often being cap])cd with nearly 
horizontal strata of the Nullagine beds, showing the mass to be a 
deeply dissected old ])lateau, 'I'he Wodgina range also stands out 
from the plains as a similar rough high hill, deeply furrowed. 
The high rough range at VVarravvoona presents quite a similar 
contrast to the ])lain country on each side of it, the latter being in 
the last stages of peneplanation, while in the ridges storm-water 
erosion is still very active. 
In the south of the State, the Stirling and Eyre Ranges show 
the same feature, rising in rugged rocky ])eaks from surrounding 
country in an advanced stage of ])lanation, quite similarly a.s the 
rocky islets on the south coast rise out of the surrounding sea. 
Jt is clear that there must be some physiographical explanation of 
the marked difference in the character of the rugged i)eaks as com- 
pared with the well-rounded hummocky country and plains round 
about them. Petrological differences have no doubt had a great 
deal to do with the tiuestion, the outstanding island-like heights of 
Wodgina, Lalla Rookh, and Warrawooiia being mostly com])osed 
of very old nietamor])hic and igneous schistose rocks, while the sur- 
rounding plains arc mostly granite, and the Stirling and Eyre 
Ranges are likewise composed of old sedimentary rocks surrounded 
by granite. In both the Pilbara and Stirling regions however, the 
rocks which form the high hills are themselves often cut down 
round the skirts of these hills quite equally with the granite, and 
are thus found extending some distance into the surrounding plains, 
as is also the case at the Rolnnson Range. It would seem most 
I)robable therefore that though these high lands stand out princi- 
Ijally through their resistance to weathering in the first instance 
l)eing greater than that of the granites round them, they have 
suffered erosi(jii round their l)ases to the same a])]-)roximate level 
as the granite round about them owing to the action of an erosive 
force acting on both without discrimination. 'Fhc only such force 
comi)etent to produce the effect as we now find it seems to the 
writer to be marine erosion, and it is therefore believed that these 
island-like hills were really islands with the waves acting round 
them to reduce the lower country to one approximate level. 
'I'he toi)ography of the country crossed over in travelling from 
Port Medland to .Marble Par is very instructive. After crossing a 
small strip of superficial limestone right at the coast, the road 
runs almost level for tniles over sandy ])lains. which gradually are 
found to have a coating of soil — usually very shallow — upon a 
I)laned-down surface of granite bed-rock. After a time occasional 
low ridges of granite and small hills of granite are encountered, 
hut the i)lain is seen to run round these and to go on inland con- 
