Geology of Castleniaine^ &c., ivitJi List of Minerals. 79 



The total amount of westerly clip shown is 2376 yards. 

 ,, ,, easterly „ 1364 „ 



excess of westerly ,, 1012 



The mean of sixty-seven observations of dip is a trifle over 70°. 

 Tf we assume this excess to be constant as far as Selwyn's 

 syncline, and assuming the dip to be, as I believe it is, at the 

 same rate, we eet in live and a half miles an excess of 7858 feet 

 of westerly dip exposed, which is equal to a thickness of 7500 

 feet. If we add 500 feet for the probable thickness exposed below 

 the Wattle Gully beds, we may put down the total thickness 

 of the lower silurian rocks exposed in this district as 8000 feet. 

 As yet we have no means of even guessing the total thickness of 

 our lower silurian rocks, and of the thickness of our upper 

 silurian we know nothing. 



Newer Rocks. 



The only other sedimentary rocks of t!ie district are the old and 

 recent river gravels. Castlemaine itself is a little over 900 feet 

 above the level of the sea, and none of the older gravels are more 

 than 1 100 feet. The latter usually occur here as cappings to minor 

 lulls, which they have protected from denudation. The linear 

 arrangement of these hills, and frequently their relation to the 

 present drainage system, shows them to be of fluviatile origin, 

 and Selwynf did not intend the general remarks he made in 

 reference to some marine tertiary gravels to apply to this 

 distinct, or to Bendigo, though it is often stated that he did so. 

 Even when the relation of the old gravels to any drainage 

 system sufficiently large for their accumulation is not apjDarent 

 at first sight, the effects of denudation must be borne in mind. 

 On this head Colonel (then Captain) Couchman, formerly Chief 

 Mining Surveyor, makes some able and interesting remarks.* 

 Taking most of his illustrations from this district, he shows how 

 changes in the courses of rivers may be made, by tributary 

 streams cutting back, and by main streams working towards 

 the dip, till another water-shed is tapped, and the old river-bed 



» Ex. Ess., 1866, p. 22. t Smyth's Goldf. and Min. Dist. of Vic, pp. 158-CO. 



