ENCLOSING DAMS. 



47 



mark, a sluice, formed of elm planks, and having an internal 

 section of 8 inches square, was fixed through the river side 

 of the dam, and rested on the lower waling. This sluice was 

 closed at the outer end by a hanging flap, to which a ring and 

 chain were attached, to lift it when required. 



The transverse struts or shores, of which there was a tier at 

 each waling, were whole timbers, and were 8 feet apart in the 

 length of the dam. Those in the upper tier were secured by 

 angle-plates and bolts reaching through the piles and walings. 

 The shores abutting against the middle and lower walings were 

 kept in place by wooden cleats bolted to the walings. To pre- 

 serve the vertical position of the dam, backstays were fixed 

 which had angle-plates attached to them, bolted through the 



T.H.W. 



Lt 



FIG. 32. 



thickness of the dam to the corresponding plates of the upper 

 row of shores. 



In the dams shown by Figs. 82 to 35, the material above 

 the clay was dredged away before the piles were driven. As 

 soon as the puddle within the dam was raised to low-water 

 level, the spaces at the front and rear were filled in with a 

 mixture of gravel and clay, to prevent the pressure of the 

 puddle from breaking the piles between the lower walings and 

 the solid ground. These sections also show the different methods 

 adopted for shoring across wide spaces. In Figs. 32, 33, the 

 width of the work was about 69 feet, and in order to avoid the 

 necessity of having so many shores of this length, the dam was 

 supported by means of buttresses, which were placed at intervals 

 of 20 feet. These buttresses were 11 feet in width, constructed 





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RONTO 



1 



