1 8
The
Subdivisious of the
Octagou,
Triangle, aud Hexagon.
—
The Oblong,
&c.
The
Suddivision
of
the Octagon,
Triangle,
and
Hexagon. (Plates 11
and
12.)
Next
to
tbe
square:
the regular
polygons most frequently occur-
ring
in ornamentation
are
the Octagon
and the Hexagon. The Triangle,
Pentagon, Decagon
and
Duodccagon are,
for obvious reasons, less
common; ^vhile the
other
regular polygons are
scarcely used
at
all.
Sometimes the
semi-regular
polygons
also appear.
These are formed
by
cutting-off
equal
triangles from
the angles of a
regular polygon
in
such
a
manner
that the
resulting
figare has long and
short sides
alternately, and
the
angles all lie
on
the circumference of a
circle.
Diagonals
and
Diameters
wth series of
lines in the
manner
of
pointed
stars,
are the
readiest
auxiliaries for
dividing regular
and
semi-regular
Polygons.
Plate
11.
The Octagon.
1
—
8.
Tbe
best-known
Subdivisions.
Plate 12.
The Tkiangle,
the
Hexagon,
&c.
1
—
5.
Simple
Subdivisions
of the
Equilateral triangle.
6
—
13.
The
best-known
Subdivisions of
the
regular
Hexagon.
14.
Subdivisions of a
regular
Pentagon.
The
Oblong, and its
Subdivision. (Plates
13
—
IG)
The
right-angled
plane figure
with
unequal
pairs of sides,
known as
an Oblong, is the most
usual
of all fundamental
forms.
Ceilings,
floors, walls, doors, wainscoting,
panels
of
furnitme,
table-
tops,
book-covers, and numbers of
other objects,
have an
oblong
shape.
The difference
in
the
lengths
of
the sides
adapts itself to
all
possible
conditions:
the Oblong
approaching
the
square on
the one
hand
and the Band
or Border on the
other;
so
that the
divisions are
very
various; as will be
seen by a
glance at
the
examples.
As
a
rule,
the
diagonal
is not used
as an
auxiliaiy line,
but is
replaced
by
the
mitral-line of the angle, as this
latter
alone
gives
equal
breadths
of the
Border. When
the Oblong
appVoaches
the
Square,
a
distorted square subdivision
is sometimes
resorted-to,
(Compare
PL
16,
lig.
2).
Plate
13. The Oblong.
1
—
6.
The usual subdivisions.
Mosaic, flooring, Italian, 16th century,
(Stored).