546 



REPOET 1882. 



supply of Dover town and castle, and moreover, as the water is abstracted from 

 the chalk, the latter will come into the condition in which it can absorb the waters 

 of the sea ; the amount so absorbed is limited by the degree of porosity of the 

 chalk, but even if the amount be only one million gallons per day, for each mile of 

 tunnel driven, it must inevitably very seriously afl'ect the construction of a tumiel 

 in this part of the chalk. 



Their areas and absorption may be taken at : — 



The height of the springs and the consequent probable height at Southampton 

 are given in the previous table. 



On the Synclinal Structure of the Straits of Dover. 

 F.O.S., Assoc. Inst. G.E. 



By W. ToPLET, 



The author briefly described the physical structure of the border of the Wealden 

 district, and showed that most of the great transverse valleys — those which drain 

 the Wealden district — lie in gentle synclinal troughs. This is the case with the 

 transverse valleys intersecting the chalk and lower greensand escarpments. The 

 Darent intersects the chalk only, and in this instance the transverse synclinal 

 aifects the chalk area only ; it does not extend so far south as the lower gi-een- 

 sand. 



The researches carried out by the French engineers over the bed of the Straits 

 of Dover, have made known the exact outcrop of the gault over the sea-bed. 

 From this it appears that the Straits coincide with a synclinal having its lowest 

 point about one-third of the way from the English shore. This represents the 

 old river valley which drained northwards through the chalk ; the higher tribu- 

 taries of this old river were the Rother and its branches, which now enter the 

 English Channel at Rye. 



It is probable that there were originally six rivers on the south side of the 

 Weald corresponding with those on the north. Only four of them now remain. 

 The fifth is represented by the Ashburn ; this now enters the sea near Pevensey, 

 but it once traversed the chalk about two miles east of Beachy Head. The sixth was 

 the Liane ; this now enters the sea at Boulogne, but it once traversed the chalk, 

 and entered the English Channel a few miles west of the French shore.' 



4. Report on the Exploration of Caves of Carboniferous Limestone in the 

 Soiith of Ireland. — See Reports, p. 240. 



' The synclinal structure of the transverse Wealden Valley was noticed by Mr. 

 A. Taylor in Geol. Mag., dec. 2, vol. i. p. 456. Further details will be found in the 

 Geological Survey Memoir on 'The Weald,' 1875, p. 276. 



I 



