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accuracy accurate acres adjusted adopted approximately assume base line bearing booked calculated centre chain circle clamped coal colliery column commenced compass correct cross cutting Describe determined dial difference direction distance divided divisions drawing drawn equal error example feet field figures fixed given gives graduated ground height horizontal inch inclination joining length magnetic meridian manner marked means measurements method mines minutes moved necessary needle notes object observation obtained offsets ordinary parallel perpendicular placed plate plotted portion position practice protractor reading reduced represent right angles rise road scale screw seam seen shaft shown side sight Southern square staff station straight line surface survey taken taking telescope theodolite traverse triangle true underground usually vernier vertical yards
Page 22 - To draw a straight line at right angles to a given straight line, from a given point in the same.
Page 19 - Any two sides of a triangle are together greater than the third side.
Page 249 - A section of the strata sunk through, or, if that is not reasonably " practicable, a statement of the depth of the shaft with a section
Page 248 - Every such plan must be on a scale of not less than that of the Ordnance Survey of twenty-five inches to the mile, or on the same scale as the plan for the time being in use at the mine.
Page 16 - A diameter of a circle is a straight line drawn through the centre, and terminated both ways by the circumference.
Page 19 - When the three angles of one are equal to the three angles of the other, each to each, the adjoining diagram shews that the triangles need not be equal in all respects.
Page 12 - A plane superficies is that in which any two points being taken, the straight line between them lies wholly in that superficies.
Page 21 - To bisect a given finite straight line, that is, to divide it into two equal parts. Let AB be the given straight line; it is required to divide it into two equal parts.