the amount of timber available for construction, the amount of rainfall, etc., should be carefully noted. In addition, the engineer should note the probable quantities of excavation, embankment, and bridging per mile; the prospective fuel supply; the possibilities for business; and all other data from which an approximate estimate of the cost of the proposed railroad can be made. PRELIMINARY SURVEY The reconnaissance having been completed and a route selected, the next thing is to make a preliminary survey. This consists of an instrumental examination of the route for the following purposes: (1) to determine the relative merits of alternative routes that have been examined on the reconnaissance; (2) to obtain the necessary information for making a map and a profile of the route; (3) to furnish data from which to project the location; and (4) to determine, approximately, the amount of work to be done in the matter of clearing, grading, and bridging, and to furnish data for an approximate estimate of the cost of all materials and labor required for the proposed road. Preliminary Estimate.-In making a preliminary estimate, great accuracy is not necessary, and no time should be wasted in useless refinements of calculation. The estimate should be high enough to cover all probable cost, and a liberal allowance should be made to cover unforeseen contingencies that may develop during construction. Most experienced engineers make it a rule to add 10 % to a preliminary estimate in order to provide for contingencies. In estimating for earthwork, the cross-sections may be considered as level cuttings; that is, the cross-section surface may be considered as level unless its slope angle exceeds 10°, in which case a suitable allowance must be made for the slope. The preliminary estimate, which also includes approximate figures for material and labor required for culverts, bridges, trestles, piers, and abutments is then classified and summarized. A sample of a good form of a preliminary estimate of the cost of a proposed railroad follows: ESTIMATE OF COST-A & B RAILROAD Clearing 625 A. at $20 per A.. $ 12,500 Earth excavation: 900,000 cu. yd. at 17c..... 153,000 120,000 160,000 3,000 Borrowed embankment: 80,000 cu. yd. at 17c.... 13,600 Piling: 12,000 lin. ft. at 25c.. 3,000 Framed trestles: 300,000 ft. B. M. at $35 per M.. 10,500 First-class masonry: 2,800 cu. yd. at $12.. 33,600 Second-class masonry: 4,200 cu. yd. at $8.. 33,600 Vitrified pipe culverts: 1,800 lin. ft. at $1.50.. 2,700 The location is the operation of fitting the line to the ground in such a manner as to secure the best adjustment of the alinement and grade, consistent with an economical cost of construction. If no topographic map is available, the work of location is done directly on the ground. Ordinarily, however, a topographic party is employed in the preliminary survey and a contour map prepared. The location is then best projected on the map, and it is called a paper location. An example of such location is illustrated in Fig. 1. Here, the line follows the valley of Bear River, and the gradient is determined by the slope of the stream. The gradient adopted is .5%, or .5 ft. per station. The preliminary line is shown dotted, and the located line is drawn full. Let the grade elevation for Sta. 16 be 155 ft.; the grade elevation for Sta. 17 will, therefore, be 155 ft.+.5 ft. 155.5 ft. The grade elevation for Sta. 18 will be 155.5+.5=156 ft. By the same process, the grade elevation is found for each station shown in the plat; and by means of interpolation between two contour curves, points having the required elevation are located opposite the corresponding stations of the preliminary survey. Each point is marked by a small dot enclosed in a circle. A line joining the points thus designated will be the grade contour, or the line where the required gradient meets the surface of the ground. The tangents AB and CD are then projected so as to conform as closely as practicable to the grade contour, and a suitable curve is inserted for the intersection angle EFD. This is most conveniently done by means of a curved protractor, an illustration of which is shown in Fig. 2. This instrument, which is made of transparent material, is shifted until there is found a curve that will fit the topography and will close the angle between the tangents, as required. Curvature.-There is no fixed rule for limiting curvature, but for a permanent track it is desirable to have the curvature as easy as possible. For all ordinary traffic conditions, it is good practice to use such curves as will best conform to existing topographical conditions. Any curve up to 10° will be no obstacle to a speed of 35 mi. per hr., the average speed of passenger trains. This affords a range in curvature that will meet the requirements of most localities. ture on a railroad line is to Final Grade Lines.-The establishing of final grade 80 PT lines is illustrated in Fig. 3, where the uncompensated grade is 1.3%, and the compensation for curvature, FIG. 3 |