REPORT FOR 1897—PART II. APPENDIX NO. 10.

649

This construction is also preferably made on a separate sheet of paper. The radiais 80a0, 80b0, S0c0, and S0d0, fi g. 22, are drawn through their corresponding points on the platted picture trace (or ground line) 0o0o', and the rest^of the construction (fig. 23) is made by regarding the paper surface as the principal plane. The désignations are the same as in fig. 20. The points d, j3, a,

H —9*r

Fig. Z 3

and y, fig. 23, on the line PP0 (principal line) represent the projections of the pictured points a, b, c, and d in the principal plane; hence, their positions are found by transferring the ordinates of the pictured points to PP0 from P0 :

P0 ô = dd0 ; PG = bb0 ; P0 a — aa0, and P() y = cc0

The radiais from 8 through d, /?, a, and y locate the points d0, /?0, a0, and y0 on the line GG (or S0P0), fig. 23.

By transferring the distances $0d0, S0/G>, S0a0, and S0y0, fig. 23, to the line 80P0 from S0, fig. 22, and drawing lines through d0, yd0, a0, and y0 parallel with 0000', their intersections with the corresponding radiais S0d0, 80b0, 80a0, 80c0 will locate the platted positions of the points P, B, A, and C of the lake.

IX. TO DRAW A PLANE FIGURE ON THE GROUND PLAN, BY MEANS OF THE SO-CALLED “METHOD OF SQUARES,” IF ITS PERSPECTIVE AND THE ELEMENTS (POINT OF VIEW AND DISTANCE LINE) OF THE VERTICAL PICTURE PLANE ARE GIVEN.

If we imagine the figure covered with a net of squares, one set of its sides being parallel with



Fig. 24-

and the other set being perpendicular to the ground line, such net may be utilized to draw the outline of the figure upon the ground plan, it being only necessary to cover the pictured figure

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