1872.] S0LLAS AND JUKES-BROWNE INCLUDED ROCK-FRAGMENTS. 11 



ore at this part of Australia will reach, if not surpass, that of all the 

 old tin-mining countries combined. 



Discussion. 



Mr. Daintree commented on the enormous value of the 170 

 miles of frontage for stream-tin works exposed in Queensland. The 

 value of these alone would, according to Mr. Gregory's calculation, be 

 some =£13,000,000 ; taking an equal value for those of New South 

 Wales, there would be 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 large tracts of similar granite to that containing 

 the stanniferous veins were 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 meta- 

 morphic 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 wauld be con- 

 fined to the areas traversed by such dykes. 



3. On the Included Rock-fragments of the Cambridge Upper Green- 

 sand. By W. Johnson Sollas, Esq., and A. J. Jukes-Browne, Esq. 



(Communicated by Prof. Eamsay, F.E.S., F.G.S.) 



[Abridged.] 



From time to time fragments of various rocks have been noticed 

 in the formation of such size and angularity as to have suggested 

 the idea to two preceding observers (Mr. Bonney and Mr. Seeley) 

 that they might have been brought to their present position by the 

 agency of ice. While ignorant of the suggestions of these gentle- 

 men, we were forced independently to the same conclusion, and 

 commenced, together, an examination of the subject. Our first step 

 was to make an examination of all the erratics from the formation 

 which had been preserved in the various local collections. The fol- 

 lowing is a descriptive list of the most important of these fragments. 



Descriptive List of Rock- fragments. 



No. 1. A large cuboidal block of coarse yellowish felspathic grit, 

 very hard and compact, measuring 10 x 7 x 7 inches, subangular, 

 not much decomposed ; incrusted with coprolite, Exogyra, Spondylus 

 truncctttdus, Plicatula sigillum, and Ostrea vesiculosa. Derived pro- 

 bably from the Millstone-grit of the north of England. Collection, 

 Woodwardian Museum, signified after this by the initials W. M. 



No. 2. A very angular, roughly rhombohedral prism of purplish- 

 red indurated shale, moderately hard, measuring 9x5x5, not 



