630 Mr. James Mansergh [March 18, 



all been done, the wall having been carried up to 730 O.D., or 30 feet 

 above the bed of the river, the water passing meanwhile along the 

 left side of its old course. We have now completed a similar stank 

 on the Radnor side, and are getting out the foundation inside of it, and 

 the building of the wall and the Radnor culvert will follow in due 

 course. Then a stank of concrete will be erected up to the level of 

 730, abutting against the wall at the upper and ihner end of each 

 culvert. This stank being finished, we shall be in a position to 

 impound water behind it to the extent of 240 million gallons, and to 

 charge the two culverts (which are 16 feet in diameter) under a head 

 over the centre of 22 feet, and this combined storage and power of 

 discharge through the culverts will enable us to pass a maximum flood 

 without interfering with the conduct of the works. The excavation 

 for the foundation of the central part of the wall can then be got out, 

 and the wall be built between the two ends (which are being finished 

 with vertical joints, dovetailed in plan) up to 730, after which the 

 remaining 92 feet in height of the wall can be erected without further 

 trouble. 



"When the wall has been finished to its full height the inlet ends 

 of the two culverts will be closed. Whi st they are performing 

 their function of passing the river in its normal state, and during 

 floods, they are fitted with cast-iron trumpets or bell -mouthed inlets 

 to facilitate the entrance of the water. At the proper time these 

 castings will be removed, and the face-plate to which they are attached 

 will then become the seating of a steel caisson, which will be lowered 

 into its place by means of guides previously fixed and drawn home 

 so as to form a watertight junction by bolts inside. These doors or 

 caissons are competent to bear the pressure due to a full reservoir, viz. 

 about 560 tons, and under their protection the pipes with their valves 

 will be laid in the culverts for conveying the compensation water to 

 the measuring chambers outside. Afterwards each of the caissons 

 will be reinforced by a mass of concrete and brickwork inside the 

 culvert, so that there may be no risk of the perfect and permanent 

 soundness and watertightness of the " stop.'' In connection with the 

 measuring apparatus there will be self-recording gauges and testing 

 chambers, and turbines driven by the compensation water actuating 

 accumulator pumps for working the hydraulic valves and dynamos 

 for electric lighting. With a full reservoir the passing of the 27 

 million gallons a day of compensation water will give about 650 horse- 

 power, gross. When the reservoir is full the water will overflow the 

 whole 600-foot length of the wall, unimpeded in any way, and at the 

 time of a high flood the depth will be about 3 feet on the crest. This 

 will be a magnificent sight, which I hope some of us may live to see. 

 On each side of the valley a channel lined with masonry and concrete 

 will be constructed in front of the ends of the main wall to conduct 

 the water harmlessly down and train it into the main channel of the 

 river, which will be enclosed within masonry side walls 150 feet 

 apart. 



