Nicholson, Peter: The student's instructor in drawing and working the five orders of architecture (London, 1823)

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3, 5, G, 6, 4, F, then on E as a centre with a radius
E B describe an arc B C cutting D C at C, on F
with a radius "F C describe the semicircle C, A, K,
cutting C D at K, on 3 with a distance 3 K describe
a semicircle KL, on 4 as a centre with the radius
4 L describe a semicircle L M, on 5 as a centre with
a radius 5 M describe a semicircle M N; lastly on
C with a radius 6 N, describe a semicircle N E,
touching the centre at E, then figure I will be com-
pleted. This method will describe an elliptical vo-
lute to a given height, but not to any given w7idth,
this is only a preparation to what follows.

TO DESCRIBE AN ELLIPTICAL VOLUTE TO ANY GIVEN
HEIGHT AND PROJECION FROM THE CENTRE.

Fig. 2. Divide the given height L M into twenty-
three equal parts as before, taking the centre E ten
from the bottom, or thirteen from the top; through
N the first division above E draw N F, cutting the
diagonal line E O at F, on E as a centre, with a
radius E F, describe the dotted circle; or through
E draw P Q at right angles to the diagonal line O E,
make E P and E Q each equal E F, on F as a centre
with the distance L F, describe an arc L H, cutting
E H at right angles to L M at H, from E make E G
equal to the distance the projection of the volute is
intended to be from the centre, divide G H into six
equal parts, and set one of the parts to I; make E K
and E R each equal to the sum of the two lines E F
and G I, through the points K, P, R, Q, complete
the parallelogram A B, C D, whose sides A B, D C,