LOCKS. 171 



back and forth as required. Where cars are used altogether they are run on a track 

 laid over the posts, and placed far enough to one side to allow dumping into the forms 

 below. This method is objected to by some engineers on the ground that the dump- 

 ing tends to separate the materials, but it has been used in several locks where the fall was 

 from 25 to 3 5 feet, and no trouble of this nature was experienced. The spreading of the 

 concrete with shovels, necessary for ramming, will assist in correcting any tendency to 

 separation, should it become apparent. 



After the concrete is in the forms it must be spread out in layers 6 to 8 

 inches deep and rammed. The ramming is done with cast-iron rammers, about 6 

 inches square on the face, and weighing with the handle from 18 to 30 Ibs., according 

 to the ideas of the engineer in charge, our own experience being that where laborers 

 are kept at ramming all day considerably better results are obtained by using the 

 lighter weights. 



Valve -seats and other ironwork can be set as the masonry is built up, while bolts 

 for ladder-supports, frames, etc., can be built in by boring holes in the lagging for them 

 and letting them project to the desired amounts. 



After a section is finished it should be covered with tarpaulins for about two 

 days, or until well set, and be wetted twice a day for about two days more, if the 

 weather is warm, as a large mass of concrete is very thirsty. 



The forms can be removed in from three to five days, depending chiefly on the 

 conditions of the temperature, and any rough joints or edges in the facing should then 

 be rubbed down with a piece of wood or of soft stone. The facing is usually soft when 

 the planks are taken off, but it will quickly harden by exposure to the air and sun. 



Facing and Coping. If facing is to be used which should be done on all surfaces 

 which will be exposed in the completed work the templates for it should be put in 

 just before the layer of concrete is spread. This facing should not be less than an inch 

 thick at any point, and should be mixed with one part of cement to not more than two 

 parts of sand, as it has to stand the weather and the abrasion of boats. It should be 

 mixed with a very small proportion of water, just sufficient to make it stick together 

 when squeezed hard in the hand, but not sufficient to show after being well rammed 

 in place. The templates for it should be about 2 inches higher than the thickness 

 of the layer of loose concrete, and wider at the top than at the bottom, so they can be 

 pulled up after the concrete is rammed without disturbing it. A convenient size may 

 be made by taking a 2 -inch plank, and planing one edge down to an inch in thickness, 

 providing staples or rings on the other edge for pulling up. The plank should be in 

 lengths not exceeding 6 feet, with shorter ones for corners, etc. When a layer is finished 

 these templates are pulled out, and the facing put in and rammed in layers (which should 

 not be over 3 or 4 inches deep) with a special rammer. This may be formed of a piece of 

 bar-iron, i inch square and 4 inches long, provided with a bent handle. 



The facing may be mixed by hand, or in the mixer, dry, and wetted just before 

 being put in place. This mixing must be thoroughly done, and the sand used should 



