42 Reports and Proceedings — Geological Society of London. 



author, beyond doubt. The striae are often as distinct and fresh- 

 looking as those occurring in a Pleistocene boulder-clay. Up to the 

 present eighty definitely glaciated boulders have been secured, besides 

 the known occurrence of other erratics too large for removal. Under 

 strong pressure and movement in their bed, some of the boulders 

 exhibit evidences of abrasion ; but this produces features which cannot 

 well be confounded with those due to glaciation. The pressure that 

 has induced cleavage has caused the elongated boulders to revolve 

 partly in their bed and place their long axes parallel to the cleavage- 

 planes. In this movement some of the stones have become slightly 

 distorted, and many show the effect of fracture in the form of pseudo- 

 striation on exposed surfaces. The lines, however, are of equal size 

 and depth, and parallel to each other over wide surfaces ; while the 

 glacial strife are generallj' patchy in their occurrence, of varying 

 intensity, and divergent in direction. A series of illustrative sections 

 are described. It is considered that Mr. H. P. Woodward's suggestion, 

 that the ' boulder- clay ' had its origin from 'floating ice,' appears to 

 be most in accordance with facts. The interbedded slates and lime- 

 stones may possibly indicate the occurrence of interglacial conditions. 



2. " On a Formation known as ' Glacial Beds of Cambrian Age ' in 

 South Australia." By H. Basedow and J. D. Iliffe. (Communicated 

 by Dr. J. Malcolm Maclaren, F.G.S.) 



Some 8 miles south of Adelaide a typical exposure of the con- 

 glomerate is bounded to the east by a series of alternating quai'tzitic 

 and argillaceous bands of rock, comprising the central and westeru 

 portions of a fan-fold, partly cut off by a fault. Further evidence of 

 stress in this margin is given in the lissility, pseudo-ripplemarks, 

 contortion and fracture, and obliteration of bedding in the quartzite 

 bands, and in the pinching-out of them into lenticles and false pebbles. 

 On the west side the conglomerate is bounded by the " Tapley's Hill 

 Clay-Slates," and there is evidence from the nature of the junction 

 beds that the conglomerate itself is isoclinally folded. In that portion 

 of the conglomerate which is adjacent to its confines, ' boulders ' of 

 quartzite are apparently disrupted portions of quartzite bands, since 

 these are in alignment with the truncated portions of bands still 

 existing, and are of similar composition. The authors are not at 

 present in a position to account for the presence in the conglomerate 

 of boulders of rocks foreign to the beds that border the conglomerate, 

 or of such as possess markings comparable to glacial strife, by their 

 theory of differential earth-movements ; but they consider that 

 a boulder-bed subjected to lateral pressure would probably lend itself 

 to the production of 'false pebbles,' through the disruption of inter- 

 calated haid bands within itself or on its boundaries. 



11.— December Uh, 1907.— Sir Archibald Geikie, K.C.B., D.C.L., Sc.D., 

 Sec. R.S., President, in the Chair. 



The following communications were read : — 



1. " The Fauna! Succession in the Carboniferous Limestone (Upper 

 Avonian) of the Midland Area (North Derbyshire and North Stafford- 

 shire)." By Thomas Franklin Siblj^ B.Sc, F.G.S. 



