. A manual of the principles and practice of road-making : comprising the location, consruction, and improvement of roads (common, macadam, paved, plank, etc.) and railroads . eed with the new one only. Thus,if 2 feet has been the originalversed sine, and the features ofthe ground which is next to be \ /passed over require a curve of 6 feet versed sine to be employed, at the desired point usea versed sine of 4 feet, and thenceforward one of 6 feet. Ifthe curvature is to be lessened, the same rule applies. Reversed Curves. It is sometimes necessary to reversethe direction of a curve, and to com
. A manual of the principles and practice of road-making : comprising the location, consruction, and improvement of roads (common, macadam, paved, plank, etc.) and railroads . eed with the new one only. Thus,if 2 feet has been the originalversed sine, and the features ofthe ground which is next to be \ /passed over require a curve of 6 feet versed sine to be employed, at the desired point usea versed sine of 4 feet, and thenceforward one of 6 feet. Ifthe curvature is to be lessened, the same rule applies. Reversed Curves. It is sometimes necessary to reversethe direction of a curve, and to commence curving in acontrary manner, without allowing a straight line to in- * It is often desirable to know how far the curve will depart from themtersectiun of ths taufjeut lines. In figure 64, the distance required= FC = OC — OF = V (OAH-ACO — OA. PARABOLIC 67 143 ervene. At one chain beyond the point at which it isdesired to make the change, place a stake in the hne ofthe two last, and at it begin to use the proper versed sinein the contrary direction. PARABOLIC ARCS. The following method furnishes an easy means of ob-taining a Parabolic curve. Fig. Divide the two tangent lines , and 12, (whetherof equal or differejit lengths) into the same number of equalparts, as many as may be thought necessary. Numberthe points of division on one tangent with the odd num-bers 1, 3, 5, &c., up to the vertex; and on the other tan-gent number them, from the vertex, with the even numbers2, 4, 6, &c. Join the points 1 and 2, 3 and 4, 5 and 6, 144 THE LOCATION OF ROADS. and SO on ; and the inner intersections A, B, C, D, E, willbe points in the curve desired. To fix the points of this curve upon the ground, tallstakes naust be placed at each of the points of division ofone of the tangent lines, and two men be stationed on theother. One places himself at station 1, and directs hiseyes to station 2. The other places himself at 3, andlooks to 4. A third man, holdin
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Keywords: ., bookcentury1800, bookdecade1850, booksubjectrailroa, bookyear1853
