98 Professor Moll on Mr Blanken's Fan-Gate Sluices. 



length of the gates, D C and F G, is superior by about l-5th 

 to the length of the gates, D E and F E, it is clear, that the 

 hydrostatical pressure against the former must be superior to 

 that against D E and F E. The consequence is, that this 

 superior pressure against D C and F G, keeps the gate 

 shut, and precludes the exterior water from running through 

 the sluice in the canal. In locks of the common construction 

 the gates must open, as often as the water is highest, on the 

 concave side of the gates. In Mr Blanken's sluices, the gates 

 may be kept shut at whatever side of them the water stands 

 highest. 



Now, things being in this state, let it be required to open 

 the fan-gates, and thus give free access to the water of the 

 river. Nothing more is wanted for this purpose, but to open 

 the slides Z and Z', and shut those at O and P ; thus, the level 

 in the semicircular cases will descend to that of the canal. The 

 hydrostatic pressure will be the strongest against the parts 

 D E and E F ; of course, they will yield to that superior 

 pressure, open and admit the water of the river into the canal. 



Supposing now the water to run in from the river into the 

 canal, with a difference of level of seven or eight feet, nothing 

 is more easy than to prevent any further supply of water into 

 the canal, and to shut the fan-gates against the current, which 

 seems to run through it with unbounded strength. Let down 

 the slides Z and Z', and raise those at O and P. The pres- 

 sure of the water runnina- through the conduits L M and 

 I K, against the greater surface of the gates D C and F G, is 

 more powerful than that against the smaller surface of D E 

 and F E, consequently, the stronger pressure will prevail, and 

 shut the gates leisurely against the current. The column of 

 water, which rushes through the sluice, is gradually contract- 

 ed by the shutting of the gates, and, finally, on their coming 

 together is reduced to nothing. 



If our supposition is reversed, and the water in the canal 

 stands higher than in the river, Mr Blanken's sluice may be 

 equally well managed. Let the gates A and B again be open, 

 and the fan-gates shut against the higher water of the canal. 

 It is well known, that it would be impossible to open the gates 



