EXAMPLES OF WALL SECTIONS. 143 



holding about two cubic yards, and was then lowered through 

 the water by a steam-crane, and deposited in the required posi- 

 tion. The mass was brought up in this way to the top of the 

 sheet-piling at low-water level. Above this level, the wall was 

 constructed as shown by Figs. 121, 122, by tide-work. The 

 concrete was made in the same proportions as the base, but the 

 face was formed smooth on the surface. 



The coping, 3 feet 9 inches by 1 foot 9 inches, was also 

 formed of concrete. 



Counterforts to carry the bollards were placed at distances 

 of 65 feet. 



To protect the face of the wall above the sheet-piling from 

 injury, fenders of greenheart timber 12 inches square were placed 

 at 20 feet centres. The bottom of the fenders were inserted and 

 secured 3 feet down into the sheet-piling, for which purpose the 

 top of one of the sheet-piles was cut away. At the top, the 

 fenders are secured to the wall by iron holdfasts, and finished 

 with a longitudinal elm fender 12 inches square, checked 

 between the vertical fenders. To protect the fenders, elm 

 rubbing-pieces, 12 inches by 5 inches, are fixed to the front. 

 For use when the tides are very high, longer fenders are placed 

 in pairs along the wall. 



Quay Wall at Brest. 1 The following method was adopted by 

 the French engineers in the construction of a deep-water quay 

 wall at Brest. 



The range of tide at Brest is considerable spring tides 

 rising about 20 feet and neap tides 14 feet. This range greatly 

 increased the facilities for carrying out the work, and had con- 



siderable weight in determining 

 the method of construction. 



The foundation of the wall 

 was a mound of loose rubble 

 stone, which was brought up to a 

 level of about 15 feet below low 

 F 123 " water of ordinary spring tides. 



From the top of the rubble 



mound to just above low- water level the work consisted of 

 artificial blocks of large size, deposited in two tiers or courses 

 (Fig. 123), whilst the upper part was constructed in the ordinary 

 manner by tide-work. 



1 Engineering. 



