i88 NOTES ON DOCKS AND DOCK CONSTRUCTION. 



this instance, however, on account of quicksand having been 

 met with, the sheeting was driven to a depth of 45 feet. 



Within the area enclosed by the sheeting, bearing-piles, 

 consisting of round fir timber 12 inches in diameter, were driven. 

 These piles were spaced 3 feet between centres transversely, and 

 4 feet longitudinally, down the centre, and covering a width of 

 10 feet. Special rows of piles were driven to carry the keel- 

 blocks. Each row of piles carries a longitudinal timber 12 

 inches square, and on these rest transverse timbers of the same 

 size, spaced 3 feet from centre to centre. 



The floor consists of 3 -inch planking, spiked or bolted to the 

 transverse timbers ; upon every third transverse floor timber, 

 oak beams are placed, upon which the bilge-blocks slide. 



Under the floor, and surrounding the pile heads and longi- 

 tudinal timbers, is a bed of Portland-cement concrete 5 feet 

 deep in the centre, sloping upwards to the sides (between the 

 floor timbers), one foot giving a maximum thickness under 

 the first altar of 6 feet; any water which may find its way 

 to the surface of the concrete flows to the centre, where drains 

 are provided to receive it and lead it away to the culvert. 



The sides rise at an angle of about 39 degrees. The altars 

 consist of fir timbers 10 inches wide by 11 inches in height on 

 the front face, chamfered off to 3 inches vertical face at the 

 back. These timbers run horizontally round the dock, forming 

 steps or altars 10 inches tread and 8 inches rise. Where the 

 altars cross the sloping side timbers, they are bolted as shown 

 by Fig. 171 ; one bolt passes through the centre of the altar 

 vertically, a second being driven through the face of the altar 

 diagonally, so as to enter the side timber perpendicularly. 



The side timbers are square baulks not less than 12 inches 

 square, and are supported on rows of piles spaced 3 feet apart 

 longitudinally. The lower ends abut upon and are secured to 

 the transverse floor timbers, and against square longitudinal 

 timbers forming the lowest altar. 



The floor concrete is continued up the back of the altars 

 for a height of 6 feet, and above this the altars are backed with 

 puddled clay well rammed in, so as to form a compact and 

 impervious mass. 



At a distance of 26 feet from the coping line of the dock 

 there is a second continuous line of 8-'nch tongued-and-grooved 

 sheet-piling driven well below the floor level of the dock so as 



