The Artist's Assistant, In the Study and Practice of Mechanical Sciences: Calculated for the Improvement of Genius. Illustrated with Copper-Plates (Birmingham, [ca. 1785])

34 THE ARTIST'S ASSISTANT.

fir ft bufmcfs is, to draw an ichnographical plan or
ground plot of it, which is thus performed. Hav-
ing made an exact, fquare of the fize you intend your
plan, divide the bafe and horizon into eight equal
parts, and from every divifion in the bafe to its
oppohte point in the horizon, rule perpendicular
lines ; then divide the fides into the fame number,
ruling parallel lines acrofs from point to point; fo
will your pavement be divided into fixty-four fquare
feet ; becaufe the eight feet in length, multiplied by
the fame in breadth give the number of fquare feet
or pieces of marble contained in the whole: then
rule diagonals from corner to corner ; and thus will
your ground plot appear as in fig. X.

Now, to lay this in perfpe&ive, draw another
fquare to your intended fize, and divide the bafe
line A B into eight equal parts, as before; then fix
your point of fight C in the middle of the hori-
zon D E, and from the fame point rule lines to every
divifion in the bafe A B ; after which, rule dia^o-

J o

nal lines from D to B, and from E to A, anfwer-
able to thofe in the ground plot, and your fquare
will be reduced to the triangle ABC; then from
the point F, where the diagonal D B intcrfefts the
line A C, to the oppofite interfeftion G, where the
diagonal E A croffes the line C B, rule a parallel
line, which is the abridgment of the fquare.

Then through the points where the diagonals
crofsthe reft of the lines which go from the bafe to
the point of fight, rule parallel lines, and your
fquare pavement will be laid in perfpe£Hve3 as in
iig. XI.

2, To