e previous one, we are able to draw it all within the page.

[Illustration: Fig. 254.]

Begin by setting out the square base at the angle required. Find point
_G_ by means of diagonals, and produce _AB_ to _V_, &c. Mark height of
step _Ao_, and proceed to draw the steps as already shown. Then by the
diagonals and measurements on base draw the second step and the square
inside it on which to stand the foot of the cross. To draw the cross,
raise verticals from the four corners of its base, and a line _K_ from
its centre. Through any point on this central line, if we draw a
diagonal from point _G_ we cut the two opposite verticals of the shaft
at _mn_ (see Fig. 255), and by means of the vanishing point _V_ we cut
the other two verticals at the opposite corners and thus obtain the four
points through which to draw the other sides of the square, which go to
the distant or inaccessible vanishing point. It will be seen by
carefully examining the figure that by this means we are enabled to draw
the double cross standing on its steps.

[Illustration: Fig. 255.]

[Illustration: Fig. 256.]

CXLIII

A STAIRCASE LEADING TO A GALLERY

In this figure we have made use of the devices already set forth in the
foregoing figures of steps, &c., such as the side scale on the left of
the figure to ascertain the height of the steps, the double lines drawn
to the high vanishing point of the inclined plane, and so on; but the
principal use of this diagram is to show on the perspective plane, which
as it were runs under the stairs, the trace or projection of the flights
of steps, the landings and positions of other objects, which will be
found very useful in placing figures in a composition of this kind.
It will be seen that these underneath measurements, so to speak, are
obtained by the half-distance.

CXLIV

WINDING STAIRS IN A SQUARE SHAFT

Draw square _ABCD_ in parallel perspective. Divide each side into four,
and raise verticals from each division. These verticals will mark the
positions of the steps on each wall, four in number. From centre _O_
raise vertical _OP_, around which the steps are to wind. Let _AF_ be the
height of each step. Form scale _AB_, which will give the height of each
step according to its position. Thus at _mn_ we find the height at the
centre of the square, so if we transfer this measurement to the central
line _OP_ and repeat it upwards, say to fourteen, then we have the
height of ea