for elevating and depressing Water* 329 



on as many bearers as are requisite, and to have a frame or 

 carriage for the purpose only of connecting the cylinders; 

 by these means the strength and friction of the 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 overcome any little obstacle or irregularity 

 that the peripheries of the cylinders would meet with in their 

 progress. 



The advantage of rollers over wheels has been admitted 

 even where the peripheries of the cylinders were in contact 

 With the incumbent weight resting on the top of them, as 

 wed as with the supporting plane below ; but in the case 

 above suggested they have more advantage, 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 used 

 to put the carriage or load in motion ; some without any loss 

 of water, and others with a trifling loss, compared with 

 what the lock holds. Thus, when the caisson is up, if, by 

 a cock, a portion of water be let 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 to the lock, the caissou 

 will rise, and the load of itself recede, and this would be 

 without waste of water. To put it in motion with a certain 

 portion of waste, it is presumed different ways may be found; 

 as the introduction of a portion of water from the upper canal 

 to the lock, or the discharging of it from the lock to the 

 lower level ; these would, with management, occasion the 

 caisson to rise or fall; or, if a part of the load were made 

 to shift further from, or nearer to, the fixed standards eeee, 

 it would thereby cause the action required, and perforin the 

 operation ; and it is probable that a better way than any here 

 suggested would arise, should the thing be put in practice, 

 I am, sir, 



Your obedient humble servant, 



W< burn, May 5, 1805. ROBERT SALMON. 



CfiQrli i Taylor, Esq. 



LI. M*. 



