288 NOTES ON DOCKS AND DOCK CONSTRUCTION. 



" At the first opening of the sluices, the chief attention was 

 directed to the working of the machinery ; the paddles were 

 slowly lifted and lowered sometimes singly, at other times in 

 sets of a few only, and then altogether. 



" The condition of the water on first leaving the sluices was 

 that of a rushing torrent of white foam, through which and 

 between the central sluice apertures occasional glimpses were 

 caught of the stone apron below. Commencing on one side of 

 the basin, the lines of direction of the current tended with a 

 boiling tumbling motion towards the opposite side from whence 

 they set out. In their course towards the river the tendency 

 was to oscillate from side to side, forming for the most part a 

 series of long curved lines, much broken into and disturbed by 

 an irregular action constantly going on in the central space 

 between them. While the main current, increasing in breadth 

 as it approached the river, would be running in a series of bends 

 at the rate of 8 miles and upwards an hour, the intervening 

 portions would be moving slowly and irregularly in various 

 directions. Sometimes at the close of the operations the 

 current would gradually reverse itself, and finally set into the 

 basin for a short distance, at an estimated rate of from half a 

 knot to two knots an hour. 



" Soon after the sluicing commenced, the colour of the water 

 would be seen to change. A dark brown cloud would rise, and 

 moving slowly with the rolling mass, would gradually extend 

 itself to the mouth of the basin, and out into the river. It was 

 also observed that, at a distance of about 150 feet from the head 

 of the basin, a cross mound of water would rise from 12 inches 

 to 18 inches higher than the natural level, and would fall off 

 with a long slope on the opposite side, caused apparently by the 

 impetus of the out-flowing water driving on, and heaping up the 

 comparatively still water with which it had come in sudden 

 contact. 



" The disturbance of the water was very great, and nothing 

 afloat could live in the basin while the sluices were in operation. 



"During the fourth trial of the sluices, the gates of the 

 north channel were torn from their fastenings and swept into 

 the chamber. The paddles were immediately lowered, and all 

 further sluicing operations suspended until an ex ami nation of 

 the channel and chamber had been made. It was found on 

 investigation that no damage had been sustained beyond the 



