OF A DOME OR NICHE

[Illustration: Fig. 192.]

First draw outline of the niche _GFDBA_ (Fig. 193), then at its base
draw square and circle _GOA_, _S_ being the point of sight, and divide
the circumference of the circle into the required number of parts. Then
draw semicircle _FOB_, and over that another semicircle _EOC_. The
manner of drawing them is shown in Fig. 192. From the divisions on the
circle _GOA_ raise verticals to semicircle _FOB_, which will divide it
in the same way. Divide the smaller semicircle _EOC_ into the same
number of parts as the others, which divisions will serve as guiding
points in drawing the curves of the dome that are drawn towards _D_, but
the shading must assist greatly in giving the effect of the recess.

[Illustration: Fig. 193.]

In Fig. 192 will be seen how to draw semicircles in perspective.
We first draw the half squares by drawing from centres _O_ of their
diameters diagonals to distance-point, as _OD_, which cuts the vanishing
line BS at _m_, and gives us the depth of the square, and in this we
draw the semicircle in the usual way.

[Illustration: Fig. 194. A Dome.]

CV

A DOME

First draw a section of the dome ACEDB (Fig. 194) the shape required.
Draw _AB_ at its base and _CD_ at some distance above it. Keeping these
as central lines, form squares thereon by drawing _SA_, _SB_, _SC_,
_SD_, &c., from point of sight, and determining their lengths by
diagonals _fh_, _f'h'_ from point of distance, passing through _O_.
Having formed the two squares, draw perspective circles in each, and
divide their circumferences into twelve or whatever number of parts are
needed. To complete the figure draw from each division in the lower
circle curves passing through the corresponding divisions in the upper
one, to the apex. But as these are freehand lines, it requires some
taste and knowledge to draw them properly, and of course in a large
drawing several more squares and circles might be added to aid the
draughtsman. The interior of the dome can be drawn in the same way.

[Illustration]

[Illustration: Fig. 195.]

CVI

HOW TO DRAW COLUMNS STANDING IN A CIRCLE

In Fig. 195 are sixteen cylinders or columns standing in a circle. First
draw the circle on the ground, then divide it into sixteen equal parts,
and let each division be the centre of the circle on which to raise the
column. The question is how to make each one the right width in
accordance with