Professor Moll on Mr Blanken's Fan-Gate Sluices. 97 



by the drawing, but when the gate opens, D C moves back- 

 wards in its semicircular case of masonry. 



The same takes place with the other gate E F G, which 

 equally turns on the same axis. The parts, F G and C D, are 

 of greater length, but of the same depth, than the parts D E 

 and F E. In this sluice, F G and C D are each twenty- 

 two English feet in length, whilst D E and F E are seven- 

 teen feet only. This difference in length of 'the two con- 

 nected parts of the gate, contains the principle on which its 

 action depends. The figures show, further, how the differ- 

 ent parts of the gate are braced together by framing of iron 

 and timber. 



The dotted lines, I K and L M, indicate canals or con- 

 duits through the masonry of the walls. Their apertures are 

 seen in Fig. 2 and 3, at L and I. They open a communication 

 between the exterior river- water, and the simicircular spaces in 

 which F G and C D turn. This communication may be shut 

 or opened at pleasure, by means of slides at N, O, P, Q, and 

 which are lowered or raised by iron windlasses. 



There is another similar conduit in each part of the sluice, 

 communicating from the semicircular spaces behind the fans, 

 with the water of the interior canal; they are shown by the 

 dotted lines at V W and X Y, and this communication can 

 also be shut up by slides, at Z and Z. 



It is thus that a communication may be opened or shut, 

 first, between the exterior or river-water, with the semicircular 

 spaces in which the fan-gates turn ; and, secondly, between 

 these semicircular spaces and the water of the interior canal. 



The following two cases may occur in the use of these 

 locks: the exterior water in the river Linge may be higher 

 than that in the canal, or the water in the canal may be high- 

 er than that in the Linge. In the first case, when the exterior 

 water is highest, supposing the flood gate A B to be open, it 

 is required to resist the superior force of the river-water by 

 the fan-gates alone. Let the slides N, O, P, Q, be raised, 

 and those at Z and Z' be shut or lowered ; the communication 

 between the external or river-water, and the water behind the 

 fan-gates, rises to the same level as in the river ; and as the 

 VOL. III. NO. I. JULY 1825. G 



