74 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



[March, 



Fig. 1, Plan. 



Fig. 2, Section. 



.W-Ii. 



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Refekences. 

 A, Upper leaf of sluice. B, C, D, Water chambers. E, F, 'Wickets. G, Cribwork. H, Pool of dam. I, Plank floor. J, Finders of timber. W L, Water line. 



The Btar Trap Sluice Gale, vphich is exhibited in plan and section 

 in the annexed diagrams, consists of two leaves or shutters, reclining 

 against each other so as to present a triangular vertical section, and 

 contain beneath them a space capable of being filled with water from 

 the superior level, and emptied thereof at will ; the contained angle at 

 the vertex, when the gates are up, being rather more than 100°, in 

 order that the leaves may slide easily, one over the other, which they 

 evidently would not do if the vertical angle of the uplifted gate were 

 either a right or an acute angle ; this sluice gate is raised and depressed 

 by liydrostatic pressure, applied and removed upon the principle of 

 that well known philosophical instrument called the Hydrostatic Bel- 

 lows ; in its usual form, as applied upon the Lehigh, it will not work in 

 dead water, but requires the action of a head more than sufficient to 

 «vercome the weight and friction of the gates, to enable it to be 

 manoeuvred with facility.* 



By an inspection of the diagrams it will be perceived that the leaves 



* Mr. English, formerly a contractor upon some of the works of the 

 Lehigh navigation, having for many years observed the action of the Bear 

 Trap .Sluice Gates, has conceived the idea of rendering them applicable as the 

 upper gates of Lift Locks, by placing a large air vessel under the lower leaf, 

 ■«hich bv its buoyancy enables the gates to rise m dead water : and he has 

 exhibited at the Franklin Institute a working model of a lock having the 

 Bear Trap Gates, with his attached air vessel applied as upper gates ; and. 

 though liable to some objections, there is reason to believe that tor the upper, 

 if not for both, gates of Ljft Locks only, they will prove to be a valuable 

 improvement, though it is evident that the same object may be attained by 

 the application of counter weights, but not perhaps as well as by an air vessel 



of the gate are hinged horizontally with hollow quoin joints, at some 

 distance above the floor: the hinge of the upper leaf being higher than 

 that of the lower, by something more than its thickness, so that even 

 when the gate is down there is a vacant space into which the aper- 

 ture opens from the well C, because the height of the hinge of the 

 lower leaf is fixed at about the same level as the tops of the openings 

 communicating with the well. 



Catch blocks on the under side of the upper leaf A determine the 

 height to which the rise of the gate is limited ; the well C is con- 

 stantly in communication with the vacancy beneath the gate ; the 

 water chamber B, is constantly open to the water from the upper level, 

 whilst that of the lower level flows freely into the chamber D ; it will 

 be observed that both these chambers communicate by suitable wickets 

 E, F, with the well C; now it will be evident from inspection that if the 

 wickets F, between C and D are shut, whilst the wickets E between 

 C and B are opened, the water from the upper level will enter beneath 

 the leaves with the upward hydrostatic pressure due to the head, and 

 the gate will consequently rise. Now, on the other hand, if the wickets 

 E are closed, whilst those at F are opened, the downward and lateral 

 hydrostatic pressure of the water in the upper level, acting then upon 

 the top surface A of the upper leaf, will force down the gate ; and thus 

 by simply putting the vacancy beneath the leaves of the sluice gate, 

 in communication separately with the upper and lower levels alter' 

 nately, the gate is elevated, depressed, or arrested at any stage of its 

 movement, by hydrostatic pressure alone ; the only manual labour or 



