TRANSVERSE PLAN.
This view of mining operations in works on pitching seams is as important as the longitudinal plan, if constructed for the purpose of conveying general information to those interested, as well as a guide to the management.
This is an end view of the works, and, if taken at a single point, represents but a limited portion of the under-ground operations. In the case of a shaft on a flat seam, we get the perpendicular height of the shaft, the point of intersection with the coal seam, the extent to left and right of the seam, and the course of the chambers and avenues radiating from the main levels or gangways. It also shows an end view of the parallel gangways, air-courses, and headings.
In a pitching seam it gives the dip of the coal, and the size and dip of the slope, with the location of gangways, air-courses, counter-levels, and water-drains. This view, therefore, represents only one point on the longitudinal plan, or a cross-section of the horizontal plan, on a given line. If the dip is uniform, and the plan of the works general in their style, a single view is sufficient to convey a good impression of the whole; but, if the dip varies and the plan of operation changes, it is necessary that transverse sections be taken at each point where those changes are in their maximum condition.
The horizontal plan must be constructed from the notes of the survey, or from the engineer's book; but the longitudinal and transverse sections may be made in the office, by the aid of instruments and computation.
No work of this kind is of much service if it is not correct, since the nice calculations that sometimes become necessary in mining operations, for startihg shafts, slopes, or air-courses at both ends,—that is, above and below,—require the survey to be proved as it progresses, by fore and back sights ; and when upper and lower levels are surveyed or run, every point of intersection, where the course of the cross-cut or incline can be obtained, should be marked, since they tend to confirm the distances if not the bearings. If the survey is made by double sights, or fore and aft dialling, it is plain that the two final sums of the traverse will demonstrate the agreement or the differ ence. When satisfied of the correctness of the survey, it is carefully protracted on the plan; and, to prove that the work has been properly done, we apply the compu tation of the dialling ; say we had 807 feet of westings and 208 feet of southings, we apply these numbers to the plan by scale, and, by the aid of the cross-lines or cardinal points, prove whether the latitude and longitude of the levels surveyed or laid on the plan conform to these lines.