40 Geological Relations of the 



conglomerate, and grits of various kinds, together with flinty 

 and cherty nodules, which were one of the supposed data 

 on which I based my idea of a cretaceous formation. Having 

 ground down their sections and examined them micro- 

 scopically, I have not been able to detect any organic remains ; 

 they have, therefore, had another origin. Similar pebbles 

 occur to the eastward along the Condamine creeks, and in 

 the bed of the Balonne far to the westward. 



Now, between the head of the Cogoon and the Maranoa 

 River, a small tributary to the latter, called the Umby, 

 collects from the trappean hills of Tagundo. The course of 

 the main channel is to S.W., and the waters collect from 

 elevations between 1,200 and 1,600 feet. Sandstones, partly 

 what Mitchell called black (which consist, so far as I have 

 seen them, of white pebbles of quartz held by a black 

 ferruginous cement), and partly red, as well as greyish white, 

 strike at the head of the Umby S.W. and N.E., which is 

 parallel to the strike of the Grafton Range. The dip at the 

 head of the Umby is S.E. Red gravel occurs in the Maranoa ; 

 and various red rocks distinguish the Cogoon and the sand- 

 stone formation beyond the Maranoa, at the head of which, 

 yellow sandstone, much rippled, and like those in the 

 Wianamata basin, near Paramatta, occur. 



The N.E. strike of the coarser sandstones on the Umby 

 agrees very well with the main strike of the Hawkesbury 

 rocks in New South Wales ; and the horizontal deposit of 

 the Psammite is like that of similar rocks in the Wianamata 

 region, where also the ground is frequently red. The occur- 

 rence of red rocks in all this region and far away to the 

 westward, the desert interior exhibiting masses of such 

 detritus and red sand as found by Kennedy, Sturt, and 

 Gregory, has a significance which cannot be overlooked. 



Having traced myself the beds of Hawkesbury rock into 

 the low interior along the Groyder and other western rivers 

 belonging to the basin of the Darling, and having found 

 many of them becoming red (far more so than in the coast 

 region of New South Wales), I cannot doubt that those red 

 deposits belong to some part of the Hawkesbury division of 

 the rocks above the coal ; but it is also possible that some 

 of the conglomerates of that division have been recomposed 

 in a later epoch, as seems to have been the case at Jerrawa, 

 near Yass, where a recomposed conglomerate of the kind is 

 capped by a sandstone very hard and silicified, full of leaves 

 of deciduous plants, probably of the Miocene epoch. The 



