. The railroad engineer's practice . pe and balance. Stakeswere put in on this line at the points corresponding Miththe centre of each pier and the faces of the abutments. AIjng flat wire (hoop-skirt wire) was then suspendedoverthis base line, with one end fast and the other passingover a pulley, with a weight hung to the latter end. Thecentres of the piers and faces of the abutments were thenplumbed up from the stakes, and marked, by winding,first with shoe-thread waxed, and then with white wire was afterwards suspended over the place whichthe bridge was to occupy, stretched with t
. The railroad engineer's practice . pe and balance. Stakeswere put in on this line at the points corresponding Miththe centre of each pier and the faces of the abutments. AIjng flat wire (hoop-skirt wire) was then suspendedoverthis base line, with one end fast and the other passingover a pulley, with a weight hung to the latter end. Thecentres of the piers and faces of the abutments were thenplumbed up from the stakes, and marked, by winding,first with shoe-thread waxed, and then with white wire was afterwards suspended over the place whichthe bridge was to occupy, stretched with the same weightas before, and sights taken on it from the stakes at 2, X, 94 JV and 0, using 77, K, M and P as fore-sights. It wasextremely satisfactory to Mr. Buck to find that one of themarks on the wire only varied one-half an inch, and allthe others less than three-eighths of an inch, from the tri-angulated distances. As a very interesting example of triangulation, the fol-lowing, executed by Mr. O. F. Nichols, may be described :. It was necessary to locate the Callao, Lima & OroyaRailroad over a very precipitous cliff, which was itselfinaccessible. The line was run from each direction as faras possible, to stations 620 and 1125 in the figure. At 930a point about grade could also be approached, and a smallplace was graded there, and fixed as a portion of the line. 95 The relative positions of these points were determined bytrianguldtion from the opposite side of the valley. Theywere then plotted with the line as determined on each sideof 1125 and 620, and connected on paper with properlines, and tunnels driven to connect them. In locatingthese lines on paper, it was borne in mind that the tunnelsshould always continue in the rock, and not cross anyseams that might run in from the face of the cliff. Pointson this face were therefore likewise determined by trian-gulation and plotted. On the side of the valley fromwhich the triangulations were made, there existed numer-ous Indi
Size: 1457px × 1715px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bo, bookcentury1800, bookdecade1880, bookidrailroadengineer00clee
