3t THE IMPROVEMENT OF RIVERS. 



required, without expense to the United States, sample cubes from any portions of the 

 quarry or quarries, shaped and dressed as may be directed by the Engineer. 



(c) Classification of Masonry. -The masonry will be classified as " Hollow Quoins," 

 "Special Stones," "Coping," "Pointed-face," "Rock-face," and "Backing." Hollow 

 quoins, special stones, and coping will be paid for by the cube of the least rectangular 

 figure that will contain the piece in question ; the other classes will be paid for by the 

 actual contents. 



(d) Hollow Quoins. Hollow quoins shall comprise the curved stones behind the 

 gates. They shall be well and truly shaped from selected stone, in accordance with 

 the detail drawings. The concave surfaces shall be neatly chiseled, together with such 

 portions of the convex surfaces as may be directed; the remainder of the exposed sur- 

 faces shall be fine-pointed. The beds and vertical joints shall be dressed throughout 

 without slack or want, and the stones must bond properly with the courses above and 

 below, and be laid with J-inch joints. They must be set square and plumb, and ihe 

 contractor must remedy at his own expense any defects of setting. 



(e) Special Stones. Special stones shall comprise the top course of the upper and of 

 the lower miter- wall where dressed to support the sills; the top courses of the upper 

 and lower coffer-walls; recess stones for coffer-beams, ladders, and line hooks; recess 

 quoins; end quoins; and pivot stones for gate pintles. No other stones will be classi- 

 fied as "special." The tops of all sill stones shall be fine-pointed; the rabbeted recesses 

 shall be chiseled smooth; and the down-stream corners of the tops shall be chiseled 

 to a quadrant of 2-inch radius. The exposed surfaces of other special stones shall be 

 dressed similarly to the adjacent stone of the same course, unless otherwise directed. 

 All masonry of this class shall have beds dressed entirely through, and the vertical 

 joints shall be full for 12 inches from the face, and for as much more as the stone will 

 allow. Special stone shall be laid with j|-inch joints. 



(/) Coping. Coping shall comprise the top courses of the main and wing-walls. It 

 shall have all exposed faces fine-pointed, with a quadrant of 2-inch radius on the front 

 edges where directed. The coping of the chamber and wing-walls shall be crowned 

 I inch, and that of thicker portions of the walls shall be laid to a grade for drainage. It 

 must all be of selected stone, with beds and vertical joints cut full and true throughout, 

 and shall be laid with jj-inch joints. The upper and lower ends of the river-wall, for a 

 distance of 20 feet, and sueli ]x>rtions of the upper wing- and land-wall as may be directed, 

 shall be doweled with i|-inch round iron, the dowels to extend through two and one-half 

 courses. The iron shall be furnished by the contractor, and be set in neat cement, 

 and the drilling and setting shall be carefully done as directed by the Engineer, and 

 shall be paid for under the price for " Bolt-holes in Masonry." 



(g) Pointed-face Stone. Pointed-face stone shall be used for the general faces of 

 the walls, and shall have its exposed surfaces pointed down fair and true, so that there 

 shall be no projection above the face of the stone greater than j| of an inch, and no 

 depression below, the plane of the face being accurately determined by a pitch-line on 



