210 ANNUAL REPORT 
nearer to the front wall of the form than % inch. No attempt shall be made 
to secure a definite surface between the Portland and Natural cement con- 
crete in the lowest step of the lock walls, but they shall be thoroughly 
bonded, blended and interlocked one into the other by long lap or splice 
joints in every layer deposited. 
27. When the top surface of the coping is reached it shall be finished 
after ramming by cutting off the excess with a straight edge and rubbed 
smooth and hard with a float by skilled sidewalk finishers. The wet finishing 
coat shall be of 1 to 3 mortar with torpedo sand, and shall be as thin as 
possible without exposing the stone or gravel of the concrete below. The 
coping of lock walls shall be slightly crowned in the center. 
28. The facing and coping shall show a smooth dense surface without 
pits or irregularities. This is most likely to be secured by thorough anda 
systematic ramming. 
29. Concrete shall not be laid in water nor exposed to the action of 
water until thoroughly set. Concrete or mortar shall not be made when the 
temperature is lower than 35 deg. fahr. in the shade, nor when rain is falling 
on it. All concrete work shall cease November 20th, and not be resumed 
before April 1st. Forms and molds must be left in position for not less than 
four days after concrete is deposited. Freshly deposited concrete shall be 
protected from the direct rays of the sun and from wind by boards or tar- 
paulins, and as soon as a section of wall is completed the exposed coping 
must be covered with a thick layer of sand and the whole mass of wall must 
be kept sprinkled until the concrete is thoroughly set. 
