. Handbook of railroad construction; for the use of American engineers. Containing the necessary rules, tables, and formulæ for the location, construction, equipment, and management of railroads, as built in the United States .. . Metres. BarometricalHeight. Metres. • - j CHAPTER II SURVEY. TOPOGRAPHICAL SKETCHING. 39. Topographical drawing includes -emy-thing relatingto an accurate representation upon paper, of any piece ofground. The state of cultivation, roads, town, county, andstate boundaries, and all else that
. Handbook of railroad construction; for the use of American engineers. Containing the necessary rules, tables, and formulæ for the location, construction, equipment, and management of railroads, as built in the United States .. . Metres. BarometricalHeight. Metres. • - j CHAPTER II SURVEY. TOPOGRAPHICAL SKETCHING. 39. Topographical drawing includes -emy-thing relatingto an accurate representation upon paper, of any piece ofground. The state of cultivation, roads, town, county, andstate boundaries, and all else that occurs in nature. TheFig. 13. sketching necessary in railroad surveying, however, does notembrace all of this, but only thedelineation of streams and theundulations of ground withinthat limit which affects the road,perhaps 500 feet on each side ofthe line. The making of suchsketches consists in tracing theirregular lines formed by the in-tersection of the natural surface,by a system of horizontal planes,at a vertical distance of five, ten,fifteen, or twenty feet, accordingto the accuracy required. 40. Suppose that we wish torepresent upon a horizontal sur-face a right cone. The base m771, fig. 13, is shown by the circle. SURVEY. 25 of which the diameter is w, m. If the elevation is cut bythe horizontal planes a a, b b, c c, the intersection of theseplanes with the conical surface is shown by the circles a, b,c, in plan. The less we make the horizontal distances, onplan, between the circles, the less also will be the verticaldistance between the planes. Wishing to find the elevation of any line which exists onplan, as 1, 2, 3, 3, 2, 1, we have only to find the intersectionof the verticals drawn through the points 1, 2, 3, 3, 2, 1,and the elevation lines a a, bb, rig. 14. cc; this gives us the curve 4,5, 6, 7, 6, 5, 4. 41. Again, in fig. 14, thecone is oblique, which causesthe circles on plan to becomeeccentric and elliptic. Havinggiven the horizontal line m-mrm,as before, we
Size: 1119px × 2234px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1850, booksubjectrailroadsdesignandco
