"The sum to be paid per square yard shall be ascertained as follows: The number of blocks per square yard upon which the bid of the contractor is based shall be 221. The actual average number of blocks laid per square yard be determined as follows: The City Engineer shall from time to time, during the progress of the work, measure the width of 50 to 100 courses, and from this deduce the average width of a course. The average length of the blocks is hereby fixed for the purpose of computing the number of blocks laid per square yard, at 121 inches.t " For each block or fractional part thereof that the average number laid per square yard shall exceed 221, there shall be added to the contractor's bid per square yard an amount computed at the rate of 9+ cents per block. For each block or fractional part thereof, that the average number laid per square yard shall fall short of 221, there shall be deducted from the con tractor's bid per square yard an amount computed at the rate of 9+ cents per block." According to this method, if the contractor uses narrow blocks and thin joints, the price per square yard is proportionally in creased; but if he uses thick blocks and wide joints, the price per yard is decreased. To meet the case in which a contractor should buy large blocks at a considerable reduction, it might be wise to make the amount per block to be deducted greater than that added. For convenience in applying the above method, a table is computed which gives in one column the width of 50 courses and in a second column the corresponding number of blocks per square yard. Of course, the number of blocks to a square yard would vary with the specified dimensions of the blocks and with the width of joints, which latter would vary with the different kinds of stone and even with the same kind from different quarries, and could be deter mined in any particular case only by measuring the combined width of a number of courses of blocks in the pavement. The
normal or contract number of blocks per square yard should be stated according to the quality of work desired.
Some cities buy the blocks and contract for laying them, a method which eliminates the interest of the contractor in using large blocks. In some cities it is the custom for the contractor to buy the blocks by the square yard in the pavement, in which case the contractor pays only for the blocks accepted, and has no finan cial interest in the size of the blocks or the thickness of the joints. In Great Britain it is customary to buy the blocks by weight, a method which eliminates any interest of the contractor in the size of the blocks.
Some cities require the blocks to be inspected and sorted to sizes before being piled on the street. The advantages of this are: (1) when stacked upon the street, only the outside blocks of the pile can be inspected; (2) when the blocks are being laid, the inspector has enough to do to watch the quality of the workman ship without having also to inspect the blocks; (3) removing rejected blocks from the pavement delays the opening of the street; and (4) if the blocks are sorted before being piled upon the street, different sizes are not so likely to get into the same course, and therefore the joints will be narrower.
In Cleveland, Ohio, where the specified width of the stone paving-block is from 3f. to 5 inches, the blocks are sorted into three classes. Class No. 1 includes blocks from 3+ to 3f inches, Class No. 2 blocks from 31 to 41 inches, and Class No. 3 embraces blocks from 4i to 5 inches. Blocks in Class No. 1 are marked with red paint, blocks in Class No. 2 with blue paint and those in Class No. 3 with black paint, so that when the blocks are delivered on the street each class can be easily recognized and laid by themselves in the pavement.
Some cities specify that thinner blocks shall be used on steep grades than on level portions, to improve the foothold.