TO DRAW A HORIZONTAL LINE, GIVEN IN POSITION AND MAGNITUDE, BY MEANS
OF ITS SIGHT-MAGNITUDE AND DIVIDING-POINTS.
[Illustration: Fig. 16.]
Let _AB_ (Fig. 16.) be the given line.
Find the position of the point _A_ in _a_.
Find the vanishing-point _V_, and most convenient dividing-point _M_,
of the line _AB_.
Join _aV_.
Through _a_ draw a horizontal line _ab′_ and make _ab′_ equal to the
sight-magnitude of _AB_. Join _b′M_, cutting _aV_ in _b_.
Then _ab_ is the line required.