Dropwall

Once the surface slope was reduced by adding great walls to the original falls, the chief source of damage was stopped. The increased height of fall thus created has been met by building cross walls 4 ft. to 5 ft. high at distances of 30 ft. to 40 ft below original sills or ogees, now converted into dropwalls, and by laying deep stone pavements over the brickwork in places of greatest action.

In the new mood of economy, it received a dropwall tripling rather than the thorough makeover of Leeds, Glasgow and Manchester.

Beyond the stage is a sunken orchestra, faced by a dropwall adorned with bas-reliefs, showing the chorus in their masks and cothurni, and the players resting in their dressing room, and backed by a dividing wall which curls in a semicircle around the priests' seats, and ends in two carved dolphins.

The entire work, with the exception of the upper six feet of the weir dropwall and the superstructure of the head-lock, has been completed

All openings of and under 20 feet span have deep dropwalls built from abutment to abutment, both up and down stream, with flooring between (laid in mortar) 4 or more feet below the natural level of stream-beds, at inclinations varying between 1 in 5 and 1 in 10, according to the locality; and it is expected these precautions will prevent back-scouring from the down-stream sides.

At either end were heavy floodgates, dropwalls of thickly forged iron. At different points in the day, according to no particular rhythm that anyone on the Fifth ever managed to figure, those gates would close, and the chamber would be flooded.

A dropwall took a direct hit and shuddered.