MARQUIS OF C ALIGN Y. 455 



is to be filled ; and also by making part of the water in the lock-chamber 

 ascend to the fore-bay when the lock-chamber is to be emptied. The 

 system is founded on the known properties of oscillating liquids. 



The work consists (omitting the details): — 



First. Of an aqueduct connecting the lower gate-chamber with two 

 separate reservoirs, U (upper) and L (lower), situated behind the upper 

 gate-chamber. 



Second. Of a discharging-channel or saving-basin, connecting the 

 reservoir L with the lower bay by a sluice; the other reservoir, U, com- 

 municates with the upper bay. 



Third. Of two vertical movable pipes, u, I, open at both ends, and 

 resting upon two circular openings made in the walls of the aqueduct. 

 One of these pipes, u, is placed in the reservoir communicating with the 

 upper bay, and the other, /, in the one communicating with the lower bay. 

 When these pipes are lowered upon their seats, the upper extremity of 

 the aqueduct is shut. If we raise the upper pipe, u, the water from the 

 upper bay enters the aqueduct ; if, on the contrary, we raise the lower 

 pipe, /, the water from the lock goes into the saving-basin, or vice versa, 

 according to their respective levels. 



The manner of working is as follows. Suppose the full lock is to be 

 emptied; we raise the pipe /, the water from the lock-chamber passes 

 through the acqueduct under the pipe, and enters the saving-basin, which 

 is supposed to be on a level with the lower bay. After having held the 

 pipe / raised during a few seconds for the water to acquire its velocity, 

 we drop it back upon its seat; the water in the aqueduct, having no 

 issue under the pipe /, rises in the interior of both I and u, and pours 

 over their tops into the reservoir U, connected with the upper bay. Thus, 

 on account of the living force of the moving liquid mass in the aqueduct, 

 a part of the water is carried into the upper bay. When this first oscil- 

 lation has ceased to cause the water to overflow from the pipes u and Z, 

 we recommence the same operation by raising again the pipe / ; a new 

 column of water issues from the lock ; we interrupt again its flow under 

 I, and a new oscillation produces a new overflow into the upper bay. As 

 this operation is repeated the lock is emptied, one portion into the saving- 

 basin and thence into the lower bay, another portion into the upper bay. 



AVithout entering further into the details of the operation, the results 

 may be stated as follows. 



This canal lock has been in operation since 1868, and we find: — 



First. That seven or eight oscillations suffice to fill or empty the lock 

 in five or six minutes. 



Second. That for filling the lock without using the reserve in the 

 saving-basin the volume of water taken from the lower bay is 0.41 V, 

 V being the prism of lift, so that the saving by this operation is about 

 two fifths of V. 



Third. That during the process of emptying the volume sent into the 



