7. Marginal drafts shall be neat and accurate.
S. Pitching shall be done to true lines and exact batter.
Mortar.-9. Mortar shall he mixed in a suitable box, or in a machine mixer, preferably of the batch type, and shall be kept free from foreign matter. The size of the batch and the proportions and the consistency shall be as directed by the engineer. When mixed by hand the sand and cement shall be mixed dry, the requisite amount of water then added and the mixing continued until the cement is uniformly distributed and the mass is uniform in color and homo geneous.
Laying.-10. The arrangement of courses and bond shall be as indicated on the drawings, or as directed by the engineer. Stone shall be laid to exact lines and levels, to give the required bond and thickness of mortar in beds and joints.
11. Stone shall be cleansed and dampened before laying.
12. Stone shall be well bonded, laid on its natural bed and solidly settled, into place in a full bed of mortar.
13. Stone shall not be dropped or slid over the wall, but shall be placed without jarring stone already laid.
14. Heavy hammering shall not be allowed on the wall after a course is laid.
15. Stone becoming loose after the mortar is set shall be relaid with fresh mortar.
16. Stone shall not be laid in freezing weather, unless directed by the En gineer. If laid, it shall be freed from ice, snow, or frost by warming. The sand and water used in the mortar shall be heated.
17. With precaution, a brine may be substituted for the heating of the mor tar. The brine shall consist of 1 pound of salt to 18 gallons of water, when the temperature is 32' F.; for every degree of temperature below 32° F., 1 ounce of salt shall be added.
1S. Before the mortar has set in beds and joints, it shall be removed to a depth of not less than 1 inch. Pointing shall not be done until the wall is com plete and mortar set; nor when frost is in the stone.
19. Mortar for pointing shall consist of equal parts of sand, sieved to meet the requirements, and Portland cement. In pointing, the joints shall be wet, and filled with mortar, pounded in with a "set-in" or calking tool and finished with a beading tool the width of the joint, used with a straight-edge.