Level

—1l. Lying in a horizontal line or plane. 2. The average elevation of a certain place, as sea level. 3. The altitude or elevation of a definite spot, as compared with some standard or datum line, generally the mean level of the sea. 4. An open channel along which water flows. 5. A horizontal excavation in a mine or along the course of a vein of ore. 6. A surveying instrument for determining the relative heights of two points. It has a telescope capable of accurate horizontal adjustments, and mounted upon a tripod stand. The level is used in conjunction with a graduated staff, which is held vertically on various succe ive stations. The marks on the staff which coincide with the cro wires of the telescope at each point, are carefully observed, and their difference corresponds to the difference in elevation of the various points.