TOPOGRAPHICAL PLANS.
In order to present to the inexperienced or unprofessional a comprehensive view or impression of subterraneous workings, it is necessary to present four views of the mine and its location.
1. A topographical plan.
2. A horizontal or working plan.
3. A longitudinal or side view.
4. A transverse or end view.
The topographical plan is a surface map of the mining estate, or boundaries of the mine. It shows the extent and connections of the property with surrounding lands and with the markets, and the location of the mines. A complete topographical map should also be a geological one. In addition to the boundaries, connections, locations of hills, streams, places, mines, and roads, the outcrops of all the veins or seams should be laid down, and their dips and axes given. The outcrop may be shown by a heavy black line following the strike of the seam, and the axes by blue lines running on the apex of the saddles, or in the centres of the basin; arrows pointing towards each other denote basins, or synclinal axes, and those pointing in opposite directions denote saddles, or anticlinal axes; an arrow pointing along the line of the axis denotes its elevation or depression; the direction in which the arrows point always denotes the direction of the depression.
If the estate is extensive and extends outside of the coal measures, light shades of color may be used to divide the geological formations: for instance, the coal measures may be a dark tint, the conglomerate blue, the red shale pink, and the Vespertine, or proto-Carboniferous, yellow, or some harmonizing color. The beds of ore may be crimson, and the roads may be fine double lines in black, with the railroads crossed.
When it is possible to do so with any correctness, it is important that transverse longitudinal and vertical sections should be constructed on the margins of the map. In fact, an engineer is not capable of correctly locating a shaft or mine until such sections can be constructed at least approximately. The general dip of the strata and a few trial-pits should always enable the engineer of mines to comprehend the axes, dips, and strikes of the seams or lodes; for this applies as truly to ores as to coal. We have
given on our map of the anthracite coal-fields sections of this character, which, how ever, are given more for the purpose of conveying an approximate idea of the general form and connection of our coal-fields than for local information. No geological survey or general location of axes of formation can be depended on for local operations. Each property or mining estate should be closely and carefully examined and surveyed, and the exact location of outcrops, axis, and dips laid down, before any attempt is made to develop the property; otherwise, errors which may be irreparable are always imminent.
When a mine is located, it is always done after a certain amount of inspection, and on the judgment of a practical mining superintendent. But, with the best judgment, this is a hap-hazard mode of proceeding. If the same judgment was made use of after a thorough examination and survey, with the location of the chief points on the map before it, there would be more certainty than guess-work, and in nine cases out of ten there would be good results. A mathematical and geometrical demonstration is proof to the practical judgment, and the mind may be easy under the responsibility of the vast expenditure attending the development of deep mines, which cannot be the case when it is all ventured on a guess: therefore, if $50,000 or $100,000 is not saved by a little judicious preliminary examination, much peace of mind and satisfaction cer tainly may be the result.
We do not say, however, that any surveyor or engineer may make such an examina tion and come to a satisfactory conclusion. It would be better to trust to the practical judgment of some experienced party than to depend on the investigations of an irre sponsible engineer. But we do say that even such a survey may be useful and in structive to the experienced mining superintendent if done under his instruction and eye. It would be far better, however, if the mining superintendent were capable of doing the work himself; and we think any intelligent man, capable of so responsible a situation, may so prepare himself with reasonable application.