394 Geological Society, 



Bagshot age. Similar shore-conditions probably extended into the 

 London basin ; and the beds mapped by the Survey as Lower Bagshot 

 are probably of the same age as those at Boscombe, in which case 

 nothing more than the Bracklesham is to be met with in the London 

 basin. The similarity of the leaves, &c, from Bovey Tracy to those 

 obtained by the author leads him to infer that the former also are of 

 Eocene, and not of Miocene age. The author increases the thick- 

 ness of the London Clay at Alum Bay at the expense of the Bagshot 

 beds, and diminishes that of the Bracklesham beds at Whitecliff Bay 

 by transferring part of them to the Lower Bagshot. 



3. " Notes on certain Modes of Occurrence of Gold in Australia." 

 By Richard Daintree, Esq., E.G.S. 



The author stated that he had in a previous paper (Q. J. G. S. 

 vol. xxviii. p. 271) proved the occurrence of gold in the Devonian 

 rocks of Queensland, and, further, that the auriferous tracts were 

 certainly confined to those districts in which the Devonian rocks 

 were penetrated by certain plutonic rocks, principally pyritous 

 diorites. These conclusions had since been confirmed by Mr. W. C. 

 Wilkinson and Dr. G. H. F. Ulrich ; and the facts thus established 

 are of the greatest practical importance to miners. With regard to 

 the epoch when the auriferous pyrites was deposited in the rocks, 

 the author expresses the opinion that most of the pyrites is contem- 

 poraneous with the consolidation of the rocks in which it occurs, 

 although some may have been subsequently introduced by infil- 

 tration ; but this is not common in Australia. A more common case 

 is the separation of gold generally diffused through a rock into local 

 fissures, forming strings and veins. The author thinks that all the 

 evidence goes to show that the Australian auriferous veins were 

 chiefly formed during the earliest era of great volcanic agitation 

 indicated by the condition of the stratified rocks, namely the 

 Devonian, but that they were enriched during a subsequent Tertiary 

 (probably Miocene) period of intense activity. No traces of auri- 

 ferous veins have yet been found in any Mesozoic or Cainozoic 

 deposits in Australia. 



4. " Notes on the Geology of the Island of Mauritius and the 

 adjacent Islets." By W. H. T. Power, Esq., B.A. 



The author stated that the island of Mauritius consists of an 

 elevated central plateau, bounded by an incomplete wall of volcanic 

 rock, round part of which there is a coral reef and coral sand-rock, 

 and also rocks of various colours produced by the decomposition of 

 volcanic rocks. Outside is a living coral reef. In the middle of the 

 island the old crater- wall can be distinguished, although broken ; 

 two secondary craters are also noticed. On the north slope of the 

 island there is a flow of columnar basalt to the sea. There is an 

 opening in the old coral-reef, as in the existing one opposite the 

 mouth of the Black River. Gabriel Island consists of a coral reef 

 and detrital coral rock upon a foundation of basalt, the section 

 showing in descending order : — 1. Coral stone ; 2. Conglomerate of 



