======================================================================== Intervals between |Twelve inch|Thirteen inch|Fourteen inch|Fifteen inch the Drains, | Pipe. | Pipe. | Pipe. | Pipe. in feet. | | | | ------------------+-----------+-------------+-------------+------------- 15 | 2904 | 2680 | 2489 | 2323 18 | 2420 | 2234 | 2074 | 1936 21 | 2074 | 1915 | 1778 | 1659 24 | 1815 | 1676 | 1555 | 1452 27 | 1613 | 1489 | 1383 | 1290 30 | 1452 | 1340 | 1244 | 1161 33 | 1320 | 1219 | 1131 | 1056 36 | 1210 | 1117 | 1037 | 968 39 | 1117 | 1031 | 957 | 893 42 | 1037 | 958 | 888 | 829 ======================================================================== The following table gives the number of rods per acre of drains at different distances: ===================================================================== Intervals between the Drains, in feet. | Rods per acre. ------------------------------------------+-------------------------- 15 | 176 18 | 146-2/3 21 | 125-5/7 24 | 110 27 | 97-7/9 30 | 88 33 | 80 36 | 73-1/3 39 | 67-9/13 42 | 62-6/7 ===================================================================== It may be remarked here, that tiles, moulded of the same length, vary nearly two inches when burned, according to the severity of the heat. It may be suggested, too, that the length of the tile, in the use of any machine, is entirely at the option of the maker. It is not, perhaps, an insult to our common humanity, to suggest to buyers the propriety of measuring the length as well as calibre of tiles before purchasing. In the estimates which will be made in this detail, it will be assumed that tiles will lay one foot each, with allowance for imperfections and breakage. This is as near as possible to accuracy, according to our best observation; and, besides, there is convenience in this simple estimate of one tile to one foot, which is important in practice.