APPENDIX B. 317 



36 Forms. The forms in which the concrete is to be placed must be built in 

 accordance with the drawings, and be solidly braced and held at all times rigidly in 

 position so as to secure accurately the required outlines of the masonry. No bracing 

 will be permitted to rest against any piles, trestles, track, or other support liable to 

 yielding or to vibration, and any deviation of the forms from line before or during com- 

 pleting must be at once corrected. No concrete shall be laid in any section until 

 all the posts have been lined up, braced, and partly planked to the satisfaction of the 

 Engineer. 



All form lumber shall be of long-leaf yellow-pine, of good quality, sound and well- 

 seasoned, and free from defects which would disfigure the concrete. The use of 

 warped or crooked lumber will not be permitted. The edges of all posts shall be 

 dressed, and all plank or lagging against which any facing mortar is to be placed, as 

 hereinafter specified, shall be dressed on all sides, and be of even width. Especial care 

 must be taken to secure smooth and even surfaces in the concrete, and all dressed lag- 

 ging must be neatly fitted and joined, and be shimmed where required, and must be 

 laid and kept level, with joints on the same line as the joints of the adjoining section. 

 Where the butt joints do not come on posts, they must be satisfactorily reinforced. 



Lagging shall be of by lumber, before dressing.* 



Posts shall be of 3-inch by 8-inch lumber, before dressing, spaced not more than 



feet apart, with braces at top and bottom, and intermediate braces where required. * 



Braces on the same post shall not be further apart than 7 feet, measured along the 

 post. They shall be of the following sizes : 



For lengths of 10 feet or less, of 2 -inch by 4-inch lumber, or larger, 

 ' ' 10 feet to 16 feet, of 3-inch by 4-inch ' ' 

 " 16 " to 22 " of 3-inch by 6-inch " " " 

 " 22 " to 26 " of 4-inch by 6-inch " " " 

 " above 26 feet, of 4-inch by 6-inch lumber, shored ana stiffened 

 where so directed. 



They must be provided with heels or bases of ample size, well rammed to a solid 

 bearing where required, and be secured to the posts with blocks or otherwise so that no 

 slipping can occur. Where so directed by the Engineer, additional braces and shores 

 for braces must be provided. Diagonal bracing of plank not less than 6 inches wide 

 and i inch in thickness must also be provided to hold the posts rigid in a lateral direc- 

 tion. All braces must be set as nearly as practicable at an angle of forty-five degrees 

 or less to the horizontal; where this angle is exceeded they must be reinforced, or the 

 heads of the posts must be tied to those of the opposite posts, as may be directed. 

 Where the braces support posts for battered surfaces, the angle must be proportionately 



reduced. 



If tie-rods are used instead of, or in addition to, braces, they must be not less than 



*See "Forms," Part III., Chap. II. 



