FLOATING. 



365 



Fig. 237 represents another mode of opening sluice-gates, 

 where the bar (m) is fastened back by an iron pin which fits 

 through a projecting stone at P, and can be easily withdrawn. 



[In the case of all the above sluice-gates, there is danger 

 of the gate swinging violently against the wall of the dam, 

 and being broken or injured. This is avoided by having the 



Fig. 238. Earthen dam with sluice-valve. 



hinge at a short distance from the wall, so that when the gate 

 is opened, there may be a passage for the water between the 

 hinge and the wall of the dam ; the intervening water then 

 breaks the force with which the sluice-gate swings, and 

 prevents its striking the wall. Tr.] 



It is evident that when the confined water of the reservoir 

 presses with all its weight on the whole sluice-gate, on 



