352 eANAt LbCK*. 



Improvement in the model, with what may be re4iiircd in practice, it 

 to save water will appear that the length of timbers at large will not 

 xn canal locks. ^^ ^^^^^ ^^^^ ^^^^ strength sufficient may be obtained for 

 any load. It is also evident, that, although the frftmeg 

 consist of only two bearers irt the model,' yet, at large, 

 any number may be introduced, parallel with each other, 

 and as many wheels as bearers. 



In this operation the weight of the carriage itself con- 

 tributes toward the effect, which in common cases is other- 

 wise, as generally there is an objection to the groat 

 weight required to make a carriage sufficiently strong for 

 any extraordinary purpose; and there is no doubt but, 

 by an imprsvement of the carriage, it may be made to 

 require much less than the power used in the present 

 model. The mode I should pursue would be, to make 

 the load in the wheels themselves, that is to say, the ne- 

 cessary load to produce the effect should be two solid 

 iron cylinders, running on as many bearers as are requi- 

 site, and to have a frame or carriage for the purpose only 

 • of connecting the cylinders ; by these means, the strength 

 and friction of tlie axletrees would be reduced very much, 

 and the means required then to perform the operation 

 would be only to put the body in motion, and to over- 

 come ai^y little obstacle or irregularity, that the periphe- 

 ries of the cylinders would meet with in their progress. 



The advantage of rollers over wheels ha^s been ad- 

 mitted, even where the peripheries of the cylinders were 

 in contact with the incumbent weight resting on the top 

 of them, as well as with the supporting plane below ; 

 but, in the case above suggested, they have more advan- 

 tage, being only in contact with the upholding frames. 



With respect to its operation, if any objections should 

 be found to the great animal power that would at large, 

 be required, it will occur, that various other means may 

 be nsed to put the carriage or load in motion ; some 

 without any loss of water, and others with a triflrng loss, 

 compared with what the lock holds. Thus, when the 

 caisson is up, if by a cock a portion of water be lot into 

 it, the equilibrium will be destroyed, the caisson will 

 ^ sink, and the water in the lock be raised. Again, if by 

 a pump, or other means, the water be returned from the 



caisson 



