2 3 2 NOTES ON DOCKS AND DOCK CONSTRUCTION. 



The sheeting covers the whole of the outer surface, and 

 reaches about halfway up the inner surface. 



The horizontal iron plates between the vertical girders form 

 the water-tight chamber which occupies the lower half of the 

 gates. This system of construction was adopted not so much 

 to economize a few tons of metal as to secure easy maintenance 

 and manipulation, while allowing the employment of large 

 sluices, of which there are two in each leaf, having a total area 

 of 75 feet super. 



The water-tight chamber, reached by means of the heel- and 

 mitre-posts, is of great height ; the men work standing, and the 

 FIG. 215. FIG. 217. FIG. 218. 



C| !A 



SECTION ON A B SECTION ON C D 



5 METRES 



TOP VIEW. FLOORING, RAILS, &c. REMOVED. 

 FIG. 216. 



paint inside can be renewed as easily as in the inside of 

 a ship. 



In turning, the greatest horizontal strain on the upper collar 

 and the lower pivot does not exceed 4J tons. 



Amsterdam Ship Canal Lock Gates. 1 The design and con- 

 struction of the iron sea-gates is shown by Figs. 210, 222. The 

 length from out to out of iron is 33 feet 2 inches by a height 

 of 23 feet 6 inches, the width at the centre of the leaf being 

 2 feet 7 inches. 



For making the joint against the hollow quoin, 2 a vertical 



1 M.P.I C.E., vol. Ixii. p. 9. 



2 Ibid., p. 29. 



