49 



and right before the sluice, on the bank, a solid square frame 

 should be constructed fitted with a wheel and axle to hold 

 the chain that is hooked on the tankard-lid door to open and 

 shut it. 



It is advisable never to leave this door half open, or to let 

 it open of itself by the pressure of the water inside, as on 

 such occasions the water rushes out from the half-opened lid 

 on both sides, and remains whirling, causing eddies and thus 

 undermining the fencings, by which they will gradually sink 

 and tumble down. 



Before the mouth of the sluice, the bottom should be pro- 

 tected as much as possible by fragments of stone, boulders, 

 etc. , for the outstreaming water not to hollow out a depth 

 there, which might gradually extend under and below the 

 sluice, thus underming it, and causing it to plunge forward,, or 

 swerve from its position, which might entail incalculable 

 damage. 



Instead of the above, a still better way is to secure the 

 sluice fore and aft by a fence made of sheating-piles of 

 boards firmly driven vertically into the ground, which must 

 close quite tight to prevent crabs, etc. from piercing them. 



All that precedes relates to iron cylinder sluices. If it is 

 desired to lay down a wooden gutter sluice, then only the 

 bottom should be nailed together on the ground, and then 

 laid or dragged into the bed dug for its reception, then the 

 uprights are fixed and crossed by transverse beams, 

 and the three sides be tightly planked. The seams must be 

 faced well with laths on the outside of the gutter against 



