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Spirit Leveling in Ohio: 1898 to 1916, Inclusive (Classic Reprint)
byR. B. Marshall
Paperback | January 7, 2019
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Excerpt from Spirit Leveling in Ohio: 1898 to 1916, Inclusive
Of the circuit in miles, sufficient care being given to the work to maintain this standard. For levels Of both classes careful Office adjustments are made, the small outstanding errors being distributed over the lines.
Bench marks - The standard bench marks are Of two forms. The first form is a circular bronze or aluminum tablet (0 and E, Pl. II), 31} inches in diameter and one-quarter inch thick, having a 3-inch stem, which is cemented in a drill hole in solid rock in the wall of some public building, a bridge abutment, or other substantial masonry structure. The second form (f, Pl. II), used where masonry or rock is not available, consists Of a hollow wrought-iron post 31} inches in outer diameter and 4 feet in length, which is set about 3 feet in the ground. The bottom is spread out to a width Of 10 inches in order to give a firm bearing on the earth. A bronze or aluminum-bronze cap is riveted upon the top Of the post. A third style of bench mark with abbreviated lettering (b and D, Pl. II) is used for unimportant points. This consists Of a special copper nail 15 inches in length driven through a copper washer seven-eighths inch in diameter. The tablets as well as the caps on the iron posts are appropriately lettered, and where States have cooperated in the work the fact of such co operation is indicated by the addition of the State name (g, Pl. II). A third form consists of a copper bolt 1 inch in diameter and 4 inches long, which is split at one end and expanded in a drill hole in masonry by driving on a brass wedge. But few Of this class have been used in Ohio, and their use has now been discontinued.
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Title:Spirit Leveling in Ohio: 1898 to 1916, Inclusive (Classic Reprint)Format:PaperbackDimensions:468 pages, 9 × 6 × 0.94 inPublished:January 7, 2019Publisher:FB&C LtdLanguage:English
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