186 Correspondence — Mr. A. B. Wynne. 



Other smaller, rounded, erratic boulders of red granite, locally 

 numerous on or near the eastern Salt Eange, but not entirely absent 

 to the west, are supposed by me to have been mainly released by 

 denudation from a Boulder-clay of probably Cretaceous age, which 

 only occurs in the eastern part of this range. Among these latter 

 boulders one has been found (not in situ) bearing marks of glacial 

 smoothing and striation. 



With regard to both these rounded erratic boulders and the larger 

 angular blocks, it is a question of interest, but of considerable 

 difficulty, to decide by what means they were transported. The 

 largest have no re})resentatives as to size in the neighbouring Cre- 

 taceous (?) boulder bed, the fragments in which are usually rounded. 

 Mr. Theobald suggests as their source a Paleeozoic boulder zone of 

 the range, and their derivation thence by weathering in situ ; but 

 this is im2:)ossible, for the Palgeozoic boulder beds referred to never 

 existed in the eastern Salt Eange, or in the vicinity of these blocks ! 

 They may therefore have been transported, as well as the northern 

 ones, by floating-ice. 



The smaller rounded and glaciated boulder just now mentioned 

 would suggest Cretaceous glacial conditions with some probability, 

 had it been found in situ. As it occurred in a wall (though near the 

 boulder bed), its scoring and smoothing may have taken place either 

 before or after its removal from that bed, supposing that it ever was 

 included therein — a point incapable of proof, but open to conjecture. 



At whatever period this particular boulder became glaciated, tlie 

 fact suggests that any of the similar boulders about the Salt Eange 

 may have been originally glacial erratics : also that glacial condi- 

 tions may have prevailed during any period to which the deposition 

 of these boulders can be traced, from Palaeozoic to Eecent. 



Eather than admit a possibility of connexion between recent ice- 

 work and the occurrence of these smaller granite erratics, Mr. 

 Theobald prefers to assert their derivation, proximately from the 

 Cretaceous Boulder-clay, but more immediately from weathering of 

 the latest Tertiary congh)merates, because in a few instances he has 

 found blocks of red gi-anite in the last-named beds. This view I 

 consider is untenable for two reasons, first on account of the number 

 of the red granite recent erratics, next because the general paral- 

 lelism pervading the whole of the eastern Salt Eange series, from 

 the oldest beds upwards, involves the Cretaceous Boulder-clay 

 having been buried under many hundreds of feet of earlier Tertiary 

 strata at the time when the few granite boulders of the uppermost 

 Tertiary conglomerates were enclosed.^ 



From the whole of the facts regarding these red granite erratics, 

 large and small, I think the fair inference is that red granitic rocky 

 ground, lying probably to the south of the Salt Eange, was being 



* There is some indication of a break in this Tertiary series, for apparently rolled 

 fragments of Nummulitic Limestone are found in it at various scattered horizons, 

 but the beds are all parallel. And there is no evidence that any rock of the Salt 

 Eange older than Nummulitic was being eroded during Tertiary deposition. The 

 Cretaceous (?) Olive group is, however, older than the Nummulitic, and ought to 

 have been covered during deposition of any subsequent beds. 



