130 NOTES ON DOCKS AND DOCK CONSTRUCTION. 



known Indian well foundations, by which coffer-dams are 

 entirely avoided, was introduced by Mr. J. Deas, C.E., in 1869, 

 and has been largely adopted since that date in the extensive 

 works carried out by the Clyde Trustees, notably, the Queen's 

 Dock, the river quay walls, and, more recently, the Cessnoch Dock. 



The strata generally, except where the boulder clay was met 

 with, was proved, by extensive boring, to be the worst possible 

 in which to construct such works as dock and quay walls, viz. 

 water-bearing gravel, and sand interspersed with pockets of mud. 



Owing to the immense quantity of water, the walls could 

 not, at any reasonable expense, have been constructed by ex- 

 cavating trenches in the gravel and sand to the required depth. 



To meet these conditions, a system of -cylinders was devised 

 by Mr. Deas, by the use of which the base of the walls was 

 brought up to low- water level. 



Concrete Rinf^" 



FIG. 99. 



These cylinders, constructed of concrete, have become the 

 standard pattern of foundations on the Clyde. They are gene- 

 rally triune in shape (Fig. 99); single cylinders being, however, 

 used when the conditions require them. 



The proportions adopted by Mr. Deas for the concrete are 

 5 parts of gravel, with a sufficiency of sand to fill the interstices, 

 to 1 part of Portland cement. 



The cylinders are made up of rings 2 feet 6 inches deep, 

 which are cast in movable wooden moulds placed on a suitable 

 platform. 



To facilitate lifting, the rings are divided into three and 

 four pieces alternately, so as to break joint when built into 

 the cylinders (Fig. 99). The division of the rings is effected 

 by -inch iron plates placed across the wooden moulds in the 



