APPENDIX B. 321 



frost shall injure any work which has not been properly protected, or which has been 

 placed in disregard or absence of instructions from the Engineer, the damaged work 

 shall be torn out and replaced by the contractor at his own expense. 



43. Gauges Recesses shall be left in the walls, as shown on the drawings, where 

 tile gauges and tablets may be placed later. The tablets will be 4 feet square, the 



gauges 1 8 inches wide, one feet, the other feet long. These tablets and 



gauges will be furnished by the United States, but must be set by the contractor at 

 such time as may be directed. 



44. Wing-walls. The wing-walls shall be founded on bed-rock for a distance 

 of . . . .feet into the bank from the chamber face of the land- wall; but, if later found 

 desirable, their length may be increased or diminished. 



45. Measurement. Concrete will be paid for by the cubic yard. Only the actual 

 amount of concrete in place will be estimated, deductions being made for all voids in the 

 mass. 



STONE-MASONRY. 



If the masonry is to be of stone instead of concrete, the following clauses may be 

 substituted. The faces of the chamber are supposed to be of "pointed face" stone. 



(a) Quality of Stone. All stone shall be perfectly strong, sound, hard, free from 

 injurious seams, and in all respects satisfactory to the Engineer. It shall be of quality 

 such as can be truly wrought to such lines and surfaces, whether plain or curved, as 

 may be required, and shall weigh not less than 150 pounds per cubic foot. The United 

 States reserves the right to reject any stone not deemed suitable. Stone quarried 

 during freezing weather must have been seasoned for a period deemed sufficient by the 

 Engineer before being laid in the wall. 



(b) Sample Cubes of Stone to Accompany Bid. Each bidder must deposit at this 

 office two 6-inch cubical blocks of the stone he proposes to furnish, one of face stone 

 and one of backing stone, with a statement giving the locality of the quarry from which 

 the sample is procured, and the quality of all stone delivered under these specifications 

 must be at least equal to that of the sample furnished. The sample must be truly 

 squared on all sides, and dressed as follows: One side, smooth or rubbed finished; one 

 side, fine pointed; one side, rock face; one side, bush-hammered; one side, rough 

 pointed; one side, crandalled. A bid unaccompanied by a sample block of the stone 

 offered, as above described, will not be considered. The bidder must satisfy the United 

 States of his ability to furnish acceptable stone. A certified test of crushing strength and 

 absorption must also be furnished if required.* Bidders will also state if their stone 

 has been used before, and for how many years structures built of it, if any, have been 

 satisfactorily standing. The contractor must also furnish from time to time, when so 



* For a latitude such as that of the Ohio River valley the absorption of the stone should not be more 

 than 2 or t\ per cent; for warmer latitudes, where danger from frost is less, it may be limited to 3 per cent. 



