Barrow, John [Hrsg.]: Dictionarium Polygraphicum: Or, The Whole Body of Arts Regularly Digested: Illustrated with Fifty-six Copper-Plates. In Two Volumes (Band 2) (London, 1758)

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There might alfo be more of thefe planes, wherein to find
the foot of the illuminating body, in order to come at the Sha-
dow of the object:.

Suppofe the foot of the illuminating body to be C, and the
flame B; from thefe points C and B draw lines, through the up-
per and under part of the object D, which will give the Shadow
K upon the table.

To find the Shadow of the chair A, which is placed on the
ground, determine the foot of the luminary on the table in C
on the ground; this is cleared by the following inftrucYions.

From the point of diftance, which is here fuppofed to be with-
out the limits of the paper, draw a line through the foot of the
table F ; then from the angle G, upon the table, let fall a per-
pendicular, cutting the line F in the point H ; and from H draw
a parallel to the bafe H I, which is equal to the upper part of the
table, and will direct to the thing required.

For drawing a line from the point of fight K, through the foot
of the luminary C, to the extremity of the table L; from the
fame point L let fall a perpendicular to H I, which will give
the point M.

Then from M draw a line to the point of fight K, in which
line M K will the foot of the luminary be found.

To determine the precife point, let fall a perpendicular from
the point C, which, cutting the line M K, will give the point
N for the foot of the luminary.

This point N being thus found, there will be no difficulty in
finding the Shadow of the chair A, the method being the fame
as for the other objects taught before ; that is, from the foot of
the luminary N, draw lines through all the angles of the plan o
the chair, and other lines through the upper part of the chair
from the luminary B ; thefe latter, by interfering the former,
-exprefs the bounds of the Shadow. For the reft, the figure gives
fufficient directions.

The Shadow of an ereel and inverted pyramid by torch-light,
plate XVIII, fig. i. The Shadow of an erect pyramid by torch-
light falls as it would by the light of the fun; and in both cafes
there is but one line, whereon the vertical point of the pyramid
will be found.

Upon the planes B C D E draw the diagonals E B and D C ;
through the central point F raife the perpendicular F A ; and
from the four points B C D E draw lines to the point A, and
the pyramid will be erected.

Then, to find its Shadow, draw an indefinite line from the bafis
G of the illuminating body, paffing through F; and from the
central flame of the torch H draw another line over the vertex

of

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