OCR Text |
Show used on a ( plane phnic ) table . 542 The ( whole wliolc ) ( map incap ) depends on a system of graphic triangulation , run ( from froin ) a ( base bi-ise biise ) line ; and ( from froin ) this base line the triangulation is graphically ( expanded expaiided ) on plane table sheets . The ( contour oiitour ) line , as shown ( on oil ) the map , is from a basic elevation , run by spirit level lines , and are carried ( from froin ) the basic ( lines lilies ) by means of vertical angles . ( R . 1864 . ) The contour ( lines lilies ) ( on oil ) the ( map inap ) are lines supposed to represent equal elevations above sea level , and are as correct as it is possible to ( deter- deter ) ( mine inine ) them . Enough elevations are determined throughout the area to enable a ( man mail ) to sketch those contours as near as he can depend on the scale of the map . All of the measurements that appear on the map are determined by scientific instruments , and barring a probable error which exists every place , are correct . The blue line on the map , Compl . Exh . 10 , Sheet A , represents the edge of the stream at the time the survey was made . ( R . 1865 . ) Its width and shape is determined by scientific instruments . . The straight brown lines inside of the blue lines ( indi- indi ) cate ( five-foot fivefoot ) contours , which between lines show a ( five-foot fivefoot ) fall in the river . The circles , enclosing numbers , indicate the mileage above Lees ( Perry Ferry ) , , along the center line of the stream . . ( R . . 1866 . . ) That is ascertained by traverse ; they make the map , , then simply step off a mile , and two miles , , and so forth , and simply draw this out so we can correlate the profile of the stream with the plan of the river . . |