"Thus, if a drain is 300 yards long, and the cutting 3 feet deep, 20 inches wide at the top, and 4 inches wide at the bottom, the mean width would be 12 inches (or the half of the sum of 20 and 4), and if we multiply 300, the length, by 1, the depth in yards, and by 1/3, the mean width in yards, and the product would be 100 cubic yards. The following table will serve to facilitate such calculations. _Table showing the number of Cubic Yards of Earth in each Rod (5-1/2 Yards in length), in Drains or Ditches of various Dimensions._ ================================================= DEPTH. | MEAN WIDTH. -------+------+------+------+------+------+------ Inches.|7 In. |8 In. |9 In. |10 In.|11 In.|12 In. -------+------+------+------+------+------+------ 30 |0.89 |1.02 |1.146 |1.27 |1.40 |1.53 33 |0.98 |1.12 |1.26 |1.40 |1.54 |1.68 36 |1.07 |1.22 |1.375 |1.53 |1.68 |1.83 39 |1.16 |1.324 |1.49 |1.655 |1.82 |1.986 42 |1.25 |1.426 |1.604 |1.78 |1.96 |2.14 45 |1.34 |1.53 |1.72 |1.91 |2.10 |2.29 48 |1.426 |1.63 |1.833 |2.04 |2.24 |2.444 51 |1.515 |1.73 |1.95 |2.164 |2.38 |2.60 54 |1.604 |1.83 |2.06 |2.29 |2.52 |2.75 57 |1.69 |1.935 |2.18 |2.42 |2.66 |2.90 60 |1.78 |2.036 |2.29 |2.546 |2.80 |3.056 ================================================= ================================================= DEPTH. | MEAN WIDTH. -------+------+------+------+------+------+------ Inches.|13 In.|14 In.|15 In.|16 In.|17 In.|18 In. -------+------+------+------+------+------+------ 30 |1.655 |1.78 |1.91 |2.04 |2.164 |2.29 33 |1.82 |1.96 |2.10 |2.24 |2.38 |2.52 36 |1.986 |2.14 |2.29 |2.244 |2.60 |2.75 39 |2.15 |2.32 |2.48 |2.65 |2.81 |2.98 42 |2.32 |2.495 |2.674 |2.85 |3.03 |3.21 45 |2.48 |2.67 |2.865 |3.055 |3.246 |3.438 48 |2.65 |2.85 |3.056 |3.26 |3.46 |3.667 51 |2.81 |3.03 |3.25 |3.46 |3.68 |3.896 54 |2.98 |3.20 |3.44 |3.666 |3.895 |4.125 57 |3.14 |3.38 |3.63 |3.87 |4.11 |4.354 60 |3.31 |3.564 |3.82 |4.074 |4.33 |4.584 =================================================