Geological Society of London. 571 



equal value for those of New South Wales, there -would he lying on the surface 

 something like twenty-five times the whole amount of tin annually produced in 

 Cornwall. In addition to this, there were lodes of immense length and richness. 

 At the same time there were large tracts of similar granite to that containing the 

 stanniferous veins still unexplored in other parts of Queensland. What amount^ also 

 of tin-bearing drift might exist under the tracts of basalt was still unascertained. 

 The tin and other minerals were, he observed, limited to the palaeozoic and metamor- 

 phic districts traversed by dykes, such as those mentioned in Mr. Ulrich's paper ; and 

 although very large areas of granite similar to that of the Severn river were to be 

 found in other parts of Queensland and Australia, the stanniferous portions would be 

 confined to the areas traversed by such dykes. 



3. " On tlie included Eock -fragments of the Cambridge Upper 

 Greensand." By W. Johnson Sollas and A. J. Jukes-Browne. 

 Communicated by Prof. Eamsay, F.E.S., P.G.S. 



The occurrence of numerous subangular fragments in the Upper 

 Greensand formation was so far remarkable that it had already 

 attracted the notice of two previous observers (Mr. Bonney and 

 Mr. Seeley), who bad both briefly hinted at the agency of ice. While 

 ignorant of the suggestions of these gentlemen, the authors of this 

 paper had been forced to the same conclusion. A descriptive list 

 had been prepared of the most remarkable of the included fragments. 

 The infallible signs of the Upper Greensand origin consisted in 

 incrustations of Plicaiula sigillum, Ostrea vesiculosa, and " Copro- 

 lite," without which, it was stated, the boulders would be- undistin- 

 guishable from those of the overlying drift. The following gene- 

 ralizations were then put forward : — 



1. The stones are mostly subangular ; some consist of friable 

 sandstones and shales, which could not have borne even a brief 

 journey over the ocean-bed. 



2. Many are of large size, especially when compared with the 

 fine silt in which they were embedded; the stones and silt could 

 not have been borne along by the same marine current. 



3. The stones are of various lithological characters, and might be 

 referred to granitic schistose, volcanic and sedimentary rocks, pro- 

 bably of Silurian, Old Eed Sandstone, and Carboniferous age. 



Such strata are not found in situ in the neighbourhood, and the 

 blocks must have come from Scotland or Wales. Numerous argu- 

 ments were adduced in favour of their Scottish derivation. 



The above considerations, that numerous rock-fragments, some of 

 which are very friable, have been brought from various localities 

 and yet retain their angularity, were thought sufficient evidence for 

 their transportation by ice ; the majority showed no ice-scratches, 

 but the small projDortion of scratched stones in the moraine matter 

 borne away on an iceberg, and the small percentage of ice-scratched 

 boulders in many deposits of glacial drift, show that the absence 

 of these strise is not inconsistent with the glacial origin of the in- 

 cluded fragments. Besides this the stones of the Greensand con- 

 sisted of rock, from which ice-marks would readily have been re- 

 moved by the action of water. The authors stated, however, that 

 they had found more positive evidence in a stone which was unmis- 

 takably ice-scratched, consisting of a siliceous limestone, and pre- 

 served in the Woodwardian Museum. The fauna, so far as it proved 



