LOCKS. 163 



posts, and the chocks prevent the ropes from being chafed along the coping as the boat 

 rises or falls in the lock pit. 



The ladders in the chamber should be of iron, and one should be set in the land 

 wall just above the lower gate recess, and one in the river wall just below the lower gate, 

 so the deck-hands can climb up or down as the boat enters or leaves the lock. In addi- 

 tion to these, one should be placed at the upper end in the river wall, just below the 

 gates. Where the chambers are very long intermediate ladders should be provided, 

 and if the dam is a movable one, a ladder should be placed on the outside of the river 

 wall, thirty or forty feet above the crest. 



Gauges, etc. Gauges showing the depths of water on the miter-sills should be 

 placed in the river wall, one at each end, where they can be conveniently read from the 

 land wall. They may be cut in the masonry and painted, but the best material for 

 them is tile, with the divisions and figures burned in black on a ground of white enamel. 

 This kind is easily cleaned, and is unaffected by the action of the water. 



On some locks ornamental tile panels have been built into the walls with pleasing 

 effect. Two are used, each about 3 or 4 feet square, and one in each wall, one showing 

 the number, etc., of the lock and the year of its completion, and the other displaying 

 the official crest of the United States, or that of the Engineer Corps. 



Finish of Walls. The inside edges of the coping of the land and river walls should 

 be rounded off to a radius of about 2 inches, to prevent chafing of mooring-lines. It 

 is good practice, in fact, to round off all coping edges, as they are liable otherwise to 

 become chipped and disfigured. The tops of the walls should be crowned about one 

 half-inch for drainage. 



CONCRETE LOCKS. 



General Design. The use of concrete for locks was practically untried until 1892, 

 although it had been used for other hydraulic works for many years. So far only 

 two objections have been made to it, one, that its appearance is inferior to that 

 of a lock of cut stone, the other, that it may not prove durable. The latter objection 

 can only be answered by experience, but there seems no reason why concrete should 

 not last as well at least as the softer classes of stone, since the latter are considerably 

 affected by water and by weather. Another objection sometimes urged is that a 

 concrete wall, being divided into sections, is less strong than a wall where each stone 

 is bonded, but where the foundations have been properly designed this objection has 

 no appreciable effect in practice. 



Concrete is generally used where its cost would be less than that of cut stone. 

 The materials are usually obtainable near the site, and are easily handled, and require 

 no skilled labor in placing. The last factor is frequently one of importance, since 

 masons and stone-cutters are often hard to obtain, and when obtained cannot always 

 be depended on. A concrete wall can also be built much more rapidly than one of stone. 



