THE LATE PETER EWART, ESQ. 127 
strongly attested by Mr. Hartley, the present 
engineer to the Liverpool docks. 
** Liverpool, 13th March, 1843. 
“Dear Sir,—By a letter which I have received 
from my friend Mr. Peter Ewart, it appears you 
wish me to communicate to you the nature of the 
Iron Coffer Dam, invented by my late greatly 
respected friend his father. 
** Above I send you a sketch of them in the 
manner in which they are supposed to be driven. 
“The original intention was that they should 
supersede the usual immense substance of a tim- 
ber and puddle Coffer Dam, the method being to 
east the piles of suitable length and breadth, with 
dovetailed flanges on each side of them; these 
being connected by cramp piles having counter- 
part dovetailed flanges, the whole were driven 
down to the required depth, and the small trian- 
gular interstice, formed betwixt the pile and the 
cramp filled up with grout made of mortar or 
clay, renders the whole perfectly water-tight. 
“1 have used them more or less, and with 
