30 
Estuarine Deposits . —These deposits are met with at the mouths of the large 
Northern rivers, where there are periodical tropical and semi-tropical floods. The 
rivers bring down large quantities of mud, which they deposit near their mouths, 
forming (excepting where coastal currents interfere) a kind of swampy delta, for the 
most part salt and overgrown with mangroves, composed of a black greasy 
mud, full in many places of recent petrifactions of craytish, wood, and worm tubes 
The Estuarine deposits of the South are of very slight account, for the rivers 
are comparatively small, having but short courses, and immediately on emerging 
from the gorges they have cut through the ranges discharge themselves into the 
arms of the sea, which run from the coast to the foot of the ranges. Moreover: 
they are but seldom flooded by excessive rainfall, and so bring down very little 
detritus. * ® 
Salt and Gypsum Deposits .— These belong to the Lake Basins : it is, however, 
worth noting that gypsum occurs in the form of beautiful crystals (selenite) on 
some of the elaypans in the interior. 
Sand Dimes. These occur almost everywhere along the coast by the river 
mouths, or w Here the land is low. They sometimes, as at Geraldton, reach a 
considerable height and are a source of trouble, as they are constantly travelling 
nn ess ’op carefully bushed or planted. Yerv often excellent water can be 
obtained beneath them, although that under the neighbouring flats may be bad. 
Piawis.—Tho sand plains follow tlie coast in the Southern portion of 
n. o ony, ex eiu up to the ranges, and cover most of the lower ground. The 
18 much loo f r than in the interior, and is often of considerable thick- 
orSu 1 Is Eohln rGd C ° l0U1 ' aild showiu S a falsa bedding, which proves that its 
25 mile, intad, „d i, f,™ 12 A"“S.'Sfe “ ^^£“3 
salt grass and samphire. Recent 0 i 10 n« sunace is coveieu 
Hinkincr n well » •+ 1 w fa&M are found here and there, and m 
Sinking a well a shelly deposit, several feet m thickness, containing suecimens of 
existing forms, was passed through. raining s P ecime 
Shen Marls and Gravels .-These are of frequent occurrence along the coast. 
Pleistocene. 
» szzw 1 1 *r, m r- -r: 
Colonies. They contain tnbe-clav ‘lml fWvn • L eac s °f the Eastern 
is reported that Diproiodim bones have been fmmd - Sailds ’ g ^ av ® 1, and ela y> a “ d 1 ' 
but A,fcrt °» 
sinking wells near “ 1 “ ittl ? nd “ Penl1 - wher0 ' 
with, which proves, beyond a doubt n, 4 +1 oyster and other shells are rad 
arm of the sea than it is now. The oy sirs T* tormQsA 7 a much Uv f] 
silting up of the mouth of the river „!kT llaTe exterminated by th< 
keeping it fresh or brackish for a largo V, V0V0 ' Ilts th ® iufiux of salt water 
Swan, to the West of Perth, are probaldy due^ to 7 holes in ^ 
water supply has dissolved lar»e cavern «« in +1 v fact .that a large subterranean 
river, which has caused subsidence in these placL^ 8 * 0116 beneath tke bcd of tb 
Shelly Limestones and Sandstones .—These occur .,11 1 xi 
coast, and contain fossils very similar to the W ?l al ° ng South-Wester 
preserve the nacre of the shells lug orms > ln many cases eve 
