122 
Clarke. — Xafural Ki(/ioiis in Wtsfcrn Auttfralia. 
The most valuaMe forojits of the State oec-ur in thi?^ legion, 
Jarrali aii'l Karri being of greatest iniportant.-e. 
Climate aiul topogiaphy eombine to make the Jarrah Kegion 
abnojit immune from the water supply problem. The streams travers- 
ing the line of the Darling fault, in beep, steep-sided valleys, are 
admirably suited for the eonstriu-tion of dams wliieh will furnish 
water to the region described next. Many of these streams are 
peruinial. Well water of fair quality, but limited quantity, is also 
available in many phu-es. In this region, however, as also in the 
main Wheat Belt, edearing and eiiltivation lead to an inerease in soil 
salinity (Wood. 1924). 
4. Pi rf]t JU'(/ion. Geologieally, this region consists of practic- 
ally undisturbed sands, clays and liniestoiies. of Becent and Tertiary 
age, overdying Mesozoic and Palaeozoic sediments, which are thought 
to di]> gtuitly S.W.. but are not known to outcrop in the region- The 
most im})ortant water carriers of the artesian province which is 
roughly ct)terniinous with the Pi rth Kegion. are thought to be the 
Jurassic sandstones (Maitland. 1919 uO. p. d). 
The country is undulating, with inconsequently scattered sand- 
hills now fixed by vegetation or cemented by carbonate of lime, 
except along the actual sea margin. The limestones formed by this 
cementation resist rain-wash better than the sands and stand up as 
low hills. Many ponds and. small lakes occur in chance hollows 
among the sand dunes, and some of these have advanced to the stage 
of peat sAvamps. which form rich soil when drained. 
The sub-recent elevation which was responsible for the emer- 
gence of the coastal })lain has b. en followed by a slight depression 
giving shallow estuaries at many of the river mouths. 
\'ery few of the rivers carry any fresh water to the sea during 
the summer- As a result of this in lennittent iiow. sea-built sand 
l»ars ol.»struct the estuaries, whoso value as harbours is thus much 
lessened. ^Moreover, the consequent ponding back of the river water 
causes rise of the water table and water-logging of the neighbouring 
hiw-lying country (Shields, p. 2). Water for use in the more 
densely settled ])arts is Ijeing increasingly drawn from reservoirs in 
the Darling Bange (Jarrah Begioii). The Perth region is however 
an artesian water basin (as already noted), and, moreover, has an 
:il,)undant supply of ground Avater at shallow depths. 
The eastern margin of this region, wliere the soil is partly de- 
rived from acid and itartly from basic rocks, is fertile (Woolnough, 
p. 16). being the chief vine-groAviug belt in the State. The outer 
