2-tO 



Mechanic force 

 faved by enlarg- 

 ing the horizon^ 

 tai fecYion of 

 the plunger. 



Remedy for 

 depofition of 



fediment. 



The machinery 

 may be worked 

 by wafte water. 



OF CONVEYING BOATS OR BARGES ON CANALS. 



Let us now fuppofe that tivo fuch plungers are joined toge- 

 ther laterally, fo as to form a new plunger, of the fame height, 

 but of twice the area and weight of the former. It is plain 

 that this new plunger (moving in a refervoir adapted to its 

 dimenfions) will by defcending four feet, raife the boat in the 

 lock as much as the other by defcending eight feet, viz. eight 

 feet: — and the momenta (confi fling of weight multiplied by 

 velocity) of both thefe plungers will be equal, becaufe the 

 product of 53 [tons] multiplied by eight [the velocity] equals 

 the product of 106 [tons] multiplied by four [the velocity] 

 each amounting to 424. 



But it will be found that, as in all cafes the height of the 

 plunger is equal to the fum of its own defcent added to that 

 of the boat's afcent, the height of this new plunger, inflead 

 of amounting to 16 feet, will only amount to 12 : its weight 

 therefore will be only 79f tons, and its momentum 318 ; it 

 will therefore require fo much the lefs time or labour to work 

 it, in the ratio of 318 to 424, or three to four. Qu. Would 

 not this objection arifing from the neceffity of having ftronger 

 machinery to fupport this latter plunger, be counterbalanced 

 by the advantage of working it with fo great a faving of labour 

 and time ? 



Should it be apprehended that, notwithftanding the forcing 

 effect of the plunger, the water in the refervoir may gradually 

 depofit fuch a quantity of fediment at the bottom as to obfrfuct 

 the defcent of the plunger, it is obvious, that there may be a 

 depending drain under the refervoir to be opened occafionally, 

 or the bottom of the refervoir itfelf may be fo much below the 

 loweft point of the plunger's defcent, as to render the cleanfing 

 it very feldom necefiary *. 



It remains to be obferved, that as every canal ought to be 

 fo well provided with water as to allow offome wafle (though 

 not enough perhaps to fupply the lofs of a lock-fall with every 

 boat that paffes) the machinery of the lock may be worked 

 thereby, without the mechanical aid commonly employed for 

 fuch purpofes ; for if the plunger preponderates over the re- 

 filling medium, and counterpoife barely enough to overcome 



* The impetus with which the water could rufh out of the refer- 

 voir into the lock, by the action of the plunger, could probably 

 raife and force out any fediment, except Hones or gravel. 



the 



