Barrow, John [Hrsg.]: Dictionarium Polygraphicum: Or, The Whole Body of Arts Regularly Digested: Illustrated with Fifty-six Copper-Plates. In Two Volumes (Band 1) (London, 1758)

204 ' D I A

The ufe of the line of the chords. As its ufe is very eafy, fb is
its convenience very great, for, placing one foot of the compaffes
at the firft divifion on the fcale, and opening the other to the
fixtieth degree, you may with the points of your compaffes, fo
extended, defcribe a circle, and the feveral divifions on the fcale
lhall be the degrees of the four quadrants of that circle, as you
may try by working backwards, to what you were juft now
taught in the making the fcale ; for, as before you meafured the
diftance of the degrees of the quadrant, and transferred them to
the fcale ; fo now you only meafure the divifions on the fcale,
and transfer them to the quadrant, femicircle, or whole circle,
defcribed on your paper. For example,

If you would meaiure thirty degrees in your defcribed circle,
place on the foot of your oompafles at the beginning of the di-
vifions on the fcale, as at A, and extend the other foot to the
divifion marked thirty, and that diftance, transferred to thecir-
cle, mail be the diftance of thirty degrees in that circle.

Do the like for any other number of degrees.

You may draw your Dial firft: on a large meet of paper, if
your Dial plane be fo large ; but, if it is not fo large, draw it on
a fmaller piece ot paper ; then rub the backfide of your paper Dial
with fmall-coal, till it be well blacked ; and laying your paper
Dial on the Dial plane, fo that the lines of your paper agree
with the eaft, v/eft, north, and fouth fituation of your Dial plane.

Then with wax or pitch fallen the corners of the paper on
the plane, and, laying a ftraight ruler on the hour lines of your
Dial, draw with the blunted point of a needle, by the fide of
the ruler, and the fmall-coal rubbed on the backfide the paper
will leave a mark of the lines on the plane.

If you would have the lines drawn red, you may rub the
backfide of your paper with vermilion ; if blue, with verditer; if
yellow, with orpiment, &c.

Then draw upon thefe marked lines with oil colours, as you
pleafe.

If your Dial decline far towards the eaft or weft, the hour
lines, unlefs projected to a very great length, will run very clofe
to one another; therefore in this cafe you muft project your
Dial on a large table, or fometimes on the floor of a room, and
cut it off as far as you think good from the center; for, t-he fur-
ther from the center, the larger the diftance of the hour lines,
aefe plate V, fig. 4..

■Of painting fun Dials, and firft -of the planes on which Dials

are to be dratvn.

Dial planes are of two forts; firft, fuch as are made on the
wall of a building ; or, fecondly, fuch as are drawn on tables of
Wood, vulgarly called J>ial boards.

The