692 REPORT— 1895. 



whicli present every sign of having been water-rolled and worn smooth by attrition. 

 The pebbles consist of white or smoky quartz, and lie imbedded in a sandy or 

 quartzitic matrix. The older rocks, from the waste of which these conglomerates 

 are derived, were probably members of the Primary Formation, on which the Wit- 

 watersrand beds lie. That these older rocks were largely veined with quartz is 

 evident from the nature of the pebbles, and that they were not the source of the 

 gold is evident from the fact that the quartz pebbles do not carry gold, the metallic 

 contents being confined to the matrix. 



There is little doubt that the gold was introduced subsequently to the deposition 

 of the beds by means of mineralising solutions, which ascended the planes of dis- 

 ruption and fissuring which resulted from the disturbance of the beds during their 

 upheaval. A considerable amount of basic igneous matter was also introduced, 

 and now appears in the beds in the form of dykes and intrusive sheets. 



The angle of dip of the auriferous beds at their outcrop is generally high 

 (50°-80°), but the lowest workings of the mines evidence a considerable flattening 

 of the deposits, the average dip in the lowest levels being at present not more than 

 30°. It is probable that the flattening will continue, and that the dip in the deep 

 level workings will be found to be not more than 25°. As these deep levels will 

 probably be worked to'a vertical depth of 4,000 to 5,000 feet, the zone of workable 

 auriferous deposit must be at least li mile wide. 



11. Report on the ' Stonesfield Slate.' — See Reports, p. ■414. 



12. On the Strata of the Shaft sunk at Stonesjield, Oxon, in 1895. 

 Jhj Edwin A. Walford, F.G.S. 



Since 1860 no continuous section of tlie upper beds of the Inferior Oolite, and 

 of the limestones intervening between them and the Stonesfield Slate, has been 

 exposed in Oxfordshire. In 1860 but brief record seems to have been made of the 

 character of the beds pierced. 



The lower part of the section made by the aid of the British Association in 

 1894-95 resolves itself readily into three divisions: — 



1. Compact buff-coloured limestones. 



2. Sandstone and sandy limestones with vertical markings and borings. 



3. Rubbly coarse-grained oolitic limestone ((/lypeus Grit) zone Ammonites 



Parkinsoni. 



Series 1 extends to the north-west as far as Long Compton, in Warwickshire, 

 and on the north to Sibford in Oxfordshire. Around Chipping Norton it is best 

 developed, but its vertical boundaries are hardly determinable. I take it to repre- 

 sent the Fullonian clays and limestones of the South and South-west of England. 

 Just as at Port-en-Bessiu and Caen, in Normandy, we see at one place the argil- 

 laceous and argillaceo-calcareous series, and at the other the calcareous and siliceo- 

 calcareous series, so also from west to east in England the deposits change from 

 argillaceous to calcareous, and with a poorer fauna. 



Series 2, generally underlying the limestones, may be traced as far as Banbury, 

 and has a wide range over Northamptonshire. A bed of Trigonia ( T. signata) marks 

 is found around Hook Norton, Chipping Norton, and Long Compton, the lower 

 part of the sandy series, with Ammonites Parkinsoni and remains of marsh plants. 

 The higher sandy limestones are recognised by the presence of long annulated 

 stems of Algae (?), extending also through the Northamptonshire deposits, and 

 characterising the higher beds there. The blue and white sandy limestone of 

 Stonesfield is full of vertical markings of plants — markings which are prominent 

 in every section of the ' Estuariue ' sands of Northamptonshire. The succession 

 of these to the bed with Trigonia signata may be seen in a quarry at Sharpshill, 

 between Brailes and Hook Norton, where a well-marked band of siliceous limestone 



