APPENDIX. 



The method is (imply thus. 



a, The loweft point of the holm, at a confiderable 

 diftance from the river, fuppofe a hundred yards. This 

 point may be lower than the point b, in the river at 

 low-water-mark j but it may be confiderably higher 

 than the point c, a confiderable way down the river, 

 fuppofe three feet. Now, if the ground b excavated 

 from c t to a, making the excavation fhallower and 

 fhallower as you approach a, where it fhould rife out 

 to the furface, it is plain, that the whole of that quar- 

 ter will be laid dry when the river falls, or arrives at 

 low-water-mark. In finking about three feet at c t 

 the breadth of the excavation is about^ twelve feet, 

 and brought to a point at a. The feftion of the 



part excavated will appear thus, 

 which has no bad effect when 



fwarded over, nor can it be perceived without a clofe 

 infpecHon. Several of the foregoing contrivances have 

 been introduced at Rafh, none of which has been 

 ever found to fail. 



T The 



