ENCLOSING DAMS. 



59 



broken off short, render- 

 ing the pulling of the 

 stumps exceedingly dif- 

 ficult. 



It may be noted with 

 regard to this dam that 



rt 



the piles being battered 

 both ways, the puddle 

 was narrower at the top 

 than at the bottom, there- 

 fore, in settling, it would 

 have a tendency to leave 

 the sides of the dam, 

 which would very greatly 

 increase the difficulty of 

 keeping it tight. 1 The 

 excessive thickness of clay 

 puddle was a great source 

 of danger, inasmuch as it 

 brought an enormous 

 strain upon the lower 

 part of the inside sheet- 

 piles where there was 

 nothing to resist the pres- 

 sure, after the removal of 

 the excavation, but a few 

 feet of quicksand; this 

 excessive pressure of the 

 clay, aided by the per- 

 colation of the water 

 through the bottom, ren- 

 dering the sand still more 

 unstable, no doubt led in 

 a very great measure to 

 the ultimate failure of the 

 dam. 



Coffer-Dam at the Vic- 

 toria Dock, Hull. 2 This 

 darn (Fig. 44) was con- 



1 M.P.I.C.K, vol. li. p. 154. 

 1 Ibid., p. 149. 



