ON THE DEAINAGE-AEEA ETC. OF THE KIVER AVON. 183 



fiting the anchorage, tends to lesson the power of the tide to keep open a 

 good deep channel in the Severn. Examination of the soundings tends to 

 conhrm this opinion ; there is an evident shoaUug of the ■water in the Severn 

 immediatelj- above the mouth of the Avon. 



The limits of this paper will not, however, permit the bringing forward all 

 that might be said on this subject, or the opportunity of showing the natural 

 as well as commercial requirements and facilities which the district afforded 

 for carrying out such a work. The scheme received, for various reasons, 

 considerable local opposition, and was ultimately left in abeyance. The 

 great outlay (about £1,000,000) which has been recently, or will very shortly 

 have been, made on dock-works connected with the Avon, and the separate 

 vested interests which have consequently arisen, have placed serious financial 

 difficulties in the way of its speedy revival. 



Within the last few years the Corporation have, through the author, as 

 their engineer, made many improvements in their existing dock-works. The 

 old lock entrances, which were not adapted to the trade of the present day, 

 have been supplemented by two new locks, of larger dimensions, laid at a 

 deeper level than the old ones, and provided with all modern appliances of 

 'hydraulic and other machinery for quick work. It would be out of place to 

 attempt to give here all the details of construction of these works. The 

 ordinary and some special diificulties were met with and overcome. These 

 chiefly arose from unsatisfactory foundations, and from having to work in 

 confined spaces surrounded by water, portions of the wall of the approach to 

 the outer entrance-lock requiring to be built in trenches on the river-bank, 

 within the line of high water, at a depth of 53 feet. In the bottom of the 

 lock excavations much trouble was experienced from springs of water from 

 the gravel bursting up through the foundation level of the lock. These were 

 overcome by building in at intervals along the lock inverts pipes reaching 

 down into the gravel, each fitted at the top with a very light gun-metal 

 valve, which, lifting easily with pressure from beneath when the tide is low, 

 permits the water to escape, and closes again when the pressure becomes 

 greater from above. These relief-valves have acted very satisfactorily. The 

 lock-gates are mostly of wrought iron, made on the arch principle, and partly 

 buoyant. In their design some special features have been adopted, which 

 may be seen in the working drawings laid before the Section for inspection 

 by any Members feeling interest in the subject. The gates work remarkably 

 well and keep practically water-tight, a somewhat unusual success in double 

 skin lock-gates. Other drawings and details of the dock-works are also open 

 for inspection. 



Improvements are also being carried on by the Corporation in the removal 

 of some of the projecting points of rock, and the deepening of the bed of the 

 river. The general line of slope to which it is proposed ultimately to re- 

 duce the bed is shown on the longitudinal section of the river (Plate YII.). 



Another important work being carried out inside of the harbour is the 

 formation of a new quay, about half a milo long, the construction of the 

 retaining- wall of which may be a matter of some interest. It is being built 

 in a trench, without a coff'er-dam, partly within and partly along the edge 

 of the water of the harbour. "With the exception of the face, which is of 

 dressed stone, and the coping, which is of granite, the whole of the wall is 

 of concrete, laid in steps and beds alternately of blue lias lime and of Portland 

 cement concrete, the object being to gain the advantage of the comparative 

 cheapness of the lime, and the more quick and certain setting of the cement. 



