350 CANAL toc^g. 



Improvement *^^e lock is raised to the top water-level d^ d; the tipper 

 to save water gates /w*, fc, are then readily opened, and the boat floated 

 in canal locks, j^^^^ ^j^^ j^^.j^ . ^^^j^ ^^^^^^ ^^^^ ^j^^^^ ^^^^^ gj^^^^ ^j^^, ^^^^^ 



and boat, by withdrawing the load from the caisson, is 

 lowered to the lower level of the canal. The lower gates 

 ?*, 2, are then opened, and the boat floated from the lock 

 to the lower canal. Tn this operation of lowering a boat 

 it is eyidentj that so far from there being a waste of 

 water, a weight of water equal to the boat and its load 

 is raised from the lower to the upper canal ; for when 

 tlie boat at the upper level first enters the lock, its own 

 weight of water is displaced, and forced into the upper 

 canal. And again, when it is floated into the lower ca- 

 nal, as much is again from that canal displaced, and 

 forced into the lock. 



On the same principle that water is gained by a de- 



"sccnding boat, as above described, it will be observed, 



that no waste ensues in an alternate passage ; and that in 



an ascending passage, a loSs of water equal to the boat 



and its load only takes place. 



It should be understood, that as canals are sometimes 

 wore or less full of water, locks on this principle must h^ 

 Constructed to raise and depress, to the greatest extremes 

 that ever happen, from the highest high-water, to tho 

 lowest low-water mark, and that being so constructed, 

 they will apply to any intermediate heights; the curved 

 plane rt being formed, to adjust and counterbalance the 

 inclination of the wheels on the other plane b, thereby 

 maintaining an equilibrium, at any intermediate height, 

 which the water in the canal may happen to be at. 



Having described its manner of operating, I, shall ex- 

 plain and compare cause and eflbct ; Ibr which purpose 

 it may be requisite first to state, that the load of the car- 

 riage B, A, is fifty-six pounds, which weight, when ad- 

 Tanced, presses directly over the parts (?, c, c, c, with all 

 its gravity bearing on the caisson ; but when the load is 

 drawn forward, it rests entirely on the fixed standards 

 f, e, e, Cy and by this change the whole eft'ect is pro- 

 doct'd. 



Now, if the model be set properly to work, it will be 

 found, that a two-pound weight suspended oyer the pul- 

 ley 



