112 Pr^of. Hughes, Criticism of the Geological [Oct. 80, 



maimer rounded masses of what looks like conglomerate are formed. 

 When the original mass happens to be a boulder clay, the included 

 striated stones are thus handed on without further wear of the 

 surface, and in this way mauy curious associations occur of rocks 

 and shells that we should not have expected to find together : 

 73, 74, 75 are examples of this. 



But in such cases as we have now under consideration we must 

 bear in mind that, in a genuine boulder clay, such as any one 

 may examine for himself on the top of Maclingley Hill, scratched 

 stones are abundant. Why then should we be expected to take 

 on trust, as evidence of glacial action in ancient times, a few 

 isolated fragments with the "ghosts of scratches" on them, when 

 good observers visiting the same spot afterwards cannot find a 

 trace ? 



xiii. Evidence of ice agency in Talchir, Karoo, and Bacchus 



Marsh beds. 



We will consider the Talchir, Karoo and North Australian 

 beds together because geographically they occur on the margin of 

 one basin, and geologically are referred to approximately the 

 same horizon. 



The Talchir beds as described by the officers of the Geological 

 Survey of India ^ consist in part of great masses of clayey silt 

 with boulders somewhat irregularly scattered through it. Gries- 

 bach suggests that they were dropped on the sea hottotn and sunk 

 in the soft mud. Beds of the same character and believed to be 

 of the same age occur in the Salt Range, in Cashmeer, and in 

 Afghanistan. They are said to rest upon a polished and striated 

 rock surface, and polished and striated boulders are recorded 

 from them, but those who have seen the beds in situ say that 

 they rely more on their similarity to boulder clays in general 

 appearance than on the occurrence of a few striated blocks here 

 and there. 



The evidence is not altogether satisfactory, as we might expect 

 a larger proportion of scratched stones in such far-transported 

 material if it were of similar origin to the boulder clay of this 

 country, and the sketches of striated blocks given do not recall 

 the commoner forms, but as I have noticed it is not easy to 

 reproduce such characters. 



1 Blanford, W. T., Blanford, H. F. and Theobald, W. Jun., Mem. Gcol. Surv. 

 Ind. 1859, Vol. i. p. 33. Record Geol. Surv. Ind., Vol. xx. Pt. i. p. 49, 1887. 

 Fedden, Becord G. Surv. Ind., Vol. viii. Pt. i. p. 16, 1875. Record Geol. Surv. 

 Ind., XIII. ii. 83. Record G. Surv. Ind., Vol. ix. Pt. iii. p. 79. Vol. xxi. Pt. i. p. 34, 

 PI. i. Vol. XXII. Pt. ii. p. 69, PI. p. 130. Vol. xix. Pt. ii. p. 133. Cf. also 

 Blanford and Medlicott. A Manual of the Geology of India, 1879. See also a good 

 resume of views in Seward, Sedgwick Prize Essay, Cambridge, 1892. 



