Notes on tlie Geology of the Country around Goulbum. 71 



(suggesting the name of Stonewall Point applied to one spot), 

 attest that they are only fragments, while the lest has been 

 swept away. The Lake instead of occupying a curvature in the 

 rocks, rests here upon the very edges of the strata ; and it is 

 difficult to conceive what has become of the rocks which must 

 have formerly filled its basin. Since the excavation of the lake, 

 the drainage of the surrounding hills has formed alluvial deposits 

 in many parts. The Lake is reported to have been dry for some 

 -time previous to 1852 ; though now full, its water is shallow and 

 brackish. Accumulations of deep alluvium stretch northwards 

 from the lake through Collector, Kose Lagoon, Lake Wologorong, 

 the Dairy Flats, and the Breadalbane Plains. 



The G-oulburn Plains, which lie along the course of the 

 Mulwaree Ponds are remarkable alluvial accumulations ; in some 

 parts they appear to the eye perfectly level for several miles, and 

 in other parts their surface is undulating. Being clothed with 

 grass, and. naturally bare of trees, they form a pleasing landscape 

 when viewed from any commanding point. Quartz is strewn 

 abundartly over some parts, as already mentioned. The only 

 apparent origin which one can assign to these plains is the 

 former action of the Mulwaree during its occasional inundations 

 in times past, before its waters had cut their way down to the 

 present levels. At present the Mulwaree consists rf a chain of 

 deep ponds, between which the water flows only after heavy 

 rs>ins. The ponds occupy mere hollows in the alluvial mud, and 

 in flood time they are liable to become filled up, whilst new ones 

 are excavated elsewhere. The deep alluvial accumulation which 

 the Mulwaree, like many other streams throughout this country, 

 now cuts through, testify a long protracted period of accumula- 

 tion at levels higher than those which now suffer inundation. 



The river terraces of the Wollondilly and Shoalhaven are 

 other instances of aqueous action. The railway cutting at the 

 Wollondilly Bridge nearest Martilan shows a section of clay and 

 gravel more than fifty feet above the river's bed ; evidently 

 deposited there when the river flowed at a level considerably 

 higher than at present; and to my mind there are proofs 

 sufficiently clear that the river once flowed even some hundred 

 feet higher above that. 



Along the Shoalhaven basin, at a distance of a few miles from 

 the river, the whole country in some parts is covered with com- 

 paratively lecent deposits ; these consist of oxides of iron, either 

 pure or mixed with clay ; also sand, grit, and gravel ; ferruginous 

 slate-breccia ; and loose waterworn pebbles and boulders. 



The deposits of oxide of iron are principally local ; the most 

 remarkable variety is a concretionary reddish hydrated oxide, 

 or pisolitic iron ore ; this occurs in several localities, as near 

 Bungonia and on Windellama Creek, and is generally found in 



