ON THE DKAINAGE-AREA ETC. OF THE RIVER AVON. 175 



EXPLANATION OF THE PLATES. 



Plate V. 



Victoria Cave, No. 1. Tliis gives a general view of the Cave and the cliffs above. Above 

 the workmen is a cavo boarded up and used as a tool-house. To the right of that 

 is a niche in the Cliff, the old entrance to tho'^Cave first discovered by Mr. Jackson. 

 The present entrance, before the excavations, was completely covered up with screes. 

 Mr. Jackson, the figure on the right, is sitting close to the arched niches mentioned at 

 p. 167. The flat in the fore ground is not a natural feature, but produced by the 

 levelling of the tip and talus. The bottom of the valley is at a far lower level. A 

 level cutting through the flat is seen going from the left-hand lower corner up to 

 the boulders. 



Plate VI. 



Victoria Cave, No. 2, gives a nearer view of the boulders near the entrance, of the rock- 

 pinnacies forming the floor, and of the arched niches described at p. 167. The 

 human relics were found near the crowbar, which is seen in the background be- 

 yond the workmen, but at a lower level. Mr. Jackson is standing between the 

 boulders and the talus, and the marked dilTerence between the two deposits is well 

 seen. The boulders before being photographed were marked S for Silurian, L for 

 Carboniferous Limestone, and Gr for Carboniferous Gritstone. The marks C°" and 

 S'* should have been C" and S'« for Conglomerate and Stalactite, and denote respec- 

 tively a piece of the conglomerate from the base of the Carboniferous Limestone, 

 and two large pieces of Stalactite, which have apparently fallen on the boulders 

 from the roof of the Cave before it had been worn as far back as it now is. 



On the River Avon {Bristol) : its Drainage- Area, Tidal Phenomena, 

 and Dock Works. By Thomas Howard, M.Inst. C.E. 



[A communication ordered by the General Committee to be printed in extenso.] 



[Plate VII.] 



The heacT-waters of the Bristol Avon may be considered to take their rise 

 in the eastern slopes of the lower CotsM'olds, to the north of Tetbury in 

 Gloucestershire, the stream gathering in from the west, in its course south- 

 ward through Malmesbury, the drainage of the oolitic district about Bad- 

 minton ; while the watershed on the east is only parted by a shght ridge 

 from the coiintry draining into the r;ppermost branches of the Thames. 

 Below this the Avon drains the Wootton-Bassett district, together with the 

 country bounded by the western outcrop of the chalk hills of Marlborough, 

 Avebury, and Beckhampton Downs, and the north-western part of Salisbiuy 

 Plain, including the towns of Calne, Devizes, Melksham, Westbury, Trow- 

 bridge, and Bradford-on-Avon. An important tributary, the Frome (Somer- 

 setshire), which brings the most southerly part of the drainage of the Avon, 

 jises near Brutou, and, embracing the watershed of the easternmost part of 

 the Mendip Hills, drains the town of Frome and several important manu- 

 facturing villages, joining the Avon at about three miles below Bradford. 

 Below this the Avon receives on the left the Midford Brook, and on the 

 right the Box and other streams ; and flowing on through Bath, receives 

 several small affluents, and at Keynsham the Chew, which springs from the 

 northern slope of the Mendips. In this district the springs from which 

 Bristol is supplied with water take their rise, at Chewton Mendip. Con- 

 tinuing its course towards Bristol, the river falls into the tideway over a weir 

 at Netham, a point about 3| miles above the entrance to the docks at 



