Clarke — Geoloyy of Western Australia. 553 



have often been noticed by explorers. In some cases tbere appears 

 a close relationship between them and igneous rocks, with which 

 silicates of alumina are connected ; but in the cases now nnder 

 notice the origin seems to be of a distinct kind. 



Whether these deposits are Recent or Tertiary, they appear to owe 

 their origin to the decomposition of felspathic granite, or such slates 

 as No. 13 ; nor is the occurrence of felspathic clays, such as haolin, 

 unknown elsewhere in Australia, for the latter exists in abundance 

 in connection with the granite of the You Yangs, near Gleelong, in 

 Victoria, from tbe decomposition of which it has resulted. Never- 

 theless, some of the Lake Lefroy beds in Mr. Hunt's list have been 

 altered by the action of some more recent igneous agent, but of 

 this no external evidence exists except in a minute fragment of some 

 dioritic rocks entangled in No. 5, though "of the fact of metamorphism 

 there is distinct evidence in Nos. 16, 28, 29, 32, 33, 34, 35, 36. 



Mr. Lefroy has positively declared, that no basalt or greenstone 

 exists in all the extensive region described by him ; we can, there- 

 fore, only regard the indications referred to as belonging to some 

 other locality from which they have been drifted, and as pointing to 

 a further succession of geological formations to the eastward or 

 north-eastward of the 122nd meridian, and a gradual approach to the 

 features and phenomena of the lower portions of the South Australian 

 territory. 



The frequency of the salt-lakes and samphire-lagoons, mentioned 

 as occupying much of the country, as well as in similar tracts of 

 Australia where flats occur in a hilly region, and the presence of 

 lime in No. o, favour the notion that the marine Tertiary beds of the 

 G-reat Bight and South Australia are not far distant to the eastward 

 of "Hunt's furthest," and of these I shall find something more 

 to say. 



I may now remark, that the quartz specimens, Nos. 14 and 31, and 

 the mention of quartz hills on the map, about eighty miles to the 

 westward, and again fifty miles south-west of that locality, as well as 

 traces of a vein in No. 1 imply, that the granites and slates are in 

 the same condition as those of auriferous tracts in Australia, whilst 

 the presence of iron pyrites in No. 4 and of the iron in Nos, 5 and 

 15 serve to establish a similar inference as to the age of granite. 



But the only economic value of the production here discussed 

 seems to belong to the iron and to the clays, of which latter deposits 

 some certainly belong to the fire-brick and porcelain species. 



The thinness of the coating of slates, clays, etc., would imply, 

 probably, a very limited supply of these products, which in many 

 cases only serve to fill in the gullies and hollows formed by erosion 

 on the granite, as in 31° 29' S., 120° 11' E., where that rock is pot- 

 holed and supports a mass not more than 100 feet thick. The 

 superficial red clay, the ferruginous red gravel, the sandy patches, the 

 rotten soft schists, the deposits of fine white sandstone, the frag- 

 ments of soft slates, all mentioned by Mr. Lefroy, are so many addi- 

 tional reasons for concluding that the region traversed by the 122nd 

 meridian is covered by a capping of the upper beds that along the 



