[ 255 ] 



arc emptied on a heap for fale ; and then 

 let down again into the boats. "I'his 

 fubterraneous canal is extended further 

 than the crane, with defign to ercd: 

 another upon the fame principles. At 

 the mouth of it is a door fiiftened on 

 hinges at the bottom of the water, which 

 falls or riles at pleafure, and when up l1:ops 

 the water from entering i a trap-door at 

 the bottom of the fubterraneous canal may 

 then be opened, and all the water let out 

 for repairing any of the works ; it then 

 runs into the channel, g. 



I fhould, in the next place, remark,, 

 that the water marked H, 11, 11, H, is 

 the river Medlockt and I, the Duke's ca- 

 nal ', but as it is the firft and grand prin- 

 ciple of Mr. Brindlcy^ plan, with all arti- 

 ficial navigations, never to let the water 

 of any brook or river intermix with that 

 of the canal, unlcfs to fupply the requilitc 

 quantity ; fome peculiar contrivance was 

 necefTary to prevent the canal, in this 

 junction with the river, from being affed:- 

 cd by its rifing or falling with flood?, GV. 

 For this purpofe, the wear was executed, 

 which is minuted in the annexed plan, 



marked 



