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water as the depth here filled up would 

 have contained : And I fliould remark, 

 that it is a maxim throughout this whole 

 navigation, to keep the canal of an equal 

 depth every where : I believe it fcarce ever 

 varies above fix inches -, from four feet, to 

 four feet fix inches. 



The method Mr. Brindley takes to fill up 

 a channel, where too deep, is a moft admi- 

 rable one ; He builds two very long boats, 

 fixes them within two feet of each other, 

 and then eredts upon them a triangular 

 trough, large enough to contain feventeen 

 tons of earth ; The bottom of this trough 

 is a line of trap doors, which, upon draw- 

 ing a pin, fiy open at once, and difcharge 

 the whole burthen in an inftant, Thefe 

 boats are filled any where from the banks 

 where the earth is in fuperfluous quanti- 

 ties, by wheel-barrowing it on a plank, 

 laid from the ihore, on to the trough: 

 The boat is then drawn over the fpot, 

 which is to be filled up, and the earth 

 there dropped : It is aftonifliing what a 

 vafl faving is made by this invention : In 

 common management to conduct a canal 

 level acrofs a valley, and without locks, 



would 



