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The Optical Delineation of a double Square.

ERE you'll find the Advantage of your folded Paper; for, applying it to the Line of the Plan, you readily mark the Points 1, 2, 3,4, 5, 6, of the visual Lines, which must be drawn to the point of sight O. Then folding the Paper cros-wie, as in P, you mark the Points 7, 8, 9, 10 placing the Points 7 on that of 6 unless you would would have the Square remov'd within the, Line of the Plan. Then from 8, 9, 10, drawing Lines to the Point of Distance E; where they interect the Line 6, 7, draw parallels to the Line of the Plan; and your Work is done.

Within the Square B, you may eaily incribe another Square by help of the Diagonals; as may be seen in the Figure.