WALL SECTIONS ON BLOCK FOUNDATIONS. 



119 



expense, the timber necessary for such a work would have been 

 very heavy, the use of caissons and compressed air was also 

 open to objection. It Avas therefore decided to adopt a series of 

 masonry curbs, placed side by side, to form the foundation of 

 the wall, and to sink them through the sand by the aid of 

 water jets to the required depth. The blocks were built on 

 the sites they were to occupy in the foundations, and were 

 constructed of masonry set in cement, resting on a base of 

 concrete 1 foot 8 inches thick (Figs. 80, 81). 



The dimensions of the smaller blocks in the foundations of 

 the north-east wall of the basin were 23 feet by 21 feet 3| inches, 



SCALE. 



50 60FLET. 



FIG. 80. 



FIG. 81. 



with an octagonal central opening or well as shown in Figs. 84 

 to 89. 



The larger curbs used in the foundations of the south-west 

 wall were made 28 feet square (Fig. 81), the weight of each being 

 800 tons. 



Two vertical grooves were left in the opposite sides of each 

 block to form keys for connecting the consecutive blocks. All 

 the blocks or curbs were allowed to stand ten days or a fortnight 

 before being sunk into place. 



The operation of sinking was performed by subjecting the 

 sand beneath the blocks to the action of powerful water jets, and 



