120 HARBOUR CONSTRUCTION. 



In the breakwater at Algiers, the proportions used for blocks 

 made on shore were 



1 part lime, in paste, 

 1 puzzuolana. 

 1 sand. 

 3 parts broken stone, 



Where concrete was deposited en masse, the proportions 

 adopted were 



1 part rich lime, in paste. 



2 parts puzzuolana. 

 4 broken stone. 



The blocks are said to have set sufficiently hard in twenty- 

 four hours to resist the shock of heavy seas. 



In addition to the breakwaters at Marseilles and Algiers, 

 lime concrete was used in those at Alexandria, Cette, and other 

 places, 



Blocks for sea-works in Italy are now commonly made of 



1 part of lime mortar, 2 of puzzuolana, and 6 of broken stone, 

 hydraulic lime being seldom used, and cement very rarely. For 

 facing-blocks the proportions generally adopted are 1 of lime, 



2 of puzzuolana, and 4 of broken stone (Min. Proc. Inter- 

 national Maritime Congress, 1893). 



The concrete blocks used in constructing the Ymuiden break- 

 waters (Holland) were composed as follows : 



FACE BLOCKS. 

 1 part Portland cement, 



3 parts sand. 



5 shingle. 



HEAKTING BLOCKS, 

 1 part Portland cement, 



4 parts sand. 



5 broken bricks. 



No blocks were used above low water until after a lapse of 

 two months in summer and three months in winter from the 

 time of their manufacture. No blocks were used below low 

 water until they were three months old. 



These blocks have not stood the rough usage to which they 

 have been subjected quite so well as could have been wished. 

 They were, however, made under exceptional difficulties, neither 

 stone, shingle, or sand of good quality being obtainable in the 

 district. 



