the quare of thé abacus, is equal to the fize of the eyé. The baichei e) of the bolters havé
lo much projecture from the abacus, that, when one foot of the compasses is placed in the
quarter of the capital (m), and the other extended to the extremity of the eymatium (n), the
circumferent line (ne) may touchthe extreme parts of the balthei. The axes of the volutes ol
are no thicker than the size of the eye, and the volutes are so inchased, that the depth is
the twellth part of their breadth. These are the proportions of capitals for columns not
more than fifteen feet high; those which are higher have their symmetry accordinoly:
THE abacus will be in length and breadth equal to the thickness of the bottom of the
column, and one ninth part; so thât, as the higher the column is, the less is its diminution.
(14*) The balthei, which signify bands or girdles, may
probably be the moldings (e), which begirt the bolster or?
profile of the volutes.
(15*) The recess (a d) of the cathetal line from the ex¬
tremity of the abacus, as described by Vitruvius, has been
generally thought too much, being one part and a half of
the eighteen parts, into which the bottom of the column is
divided, causing the cymatium or ovolo to have a very
large projection. Some therefore have supposed the text to
have been corrupted: and Palladio Alberti, Vignola, and
some others, have allowed it but one eighteenth part, intirely
suppressing the half part. Scamozzi and Barbaro have
given it one part and a quarter. The projection may be
large, but it nevertheless seems to be such as was intended
by Vitruvius; for it makes the projecture of the abacus no
more than equal to its heighth, which is conformable to his
general rule in all moldings.
As the draught of this capital, as well as the other figures,
which Vitruvius annexed at the end of his book; are lost,
it is not possible from this brief description to understand
perfectly his method of forming the volute. What has been
said above, at note 12, encourages an opinion, that it is
something like Serlio's. On the other hand, his speaking
of the operations of the several quarters, makes it supposable
that it is one of those methods in which each point turns a
quarter circle only ; whereas, if all the points are in the
cathetal line, as in Serlio's method they are, each point must
turn a semicircle.
There are many different methods in use for turning the
lonic volute, which are described in the many books of
architecture now extant, and to which therefore I refer the
reader. Nicholas Goldmanno has published a tract con¬
cerning the lonic volute of Vitruvius, where he supposes
he has discovered Vitruvius's method. It is nearly like
that method given by Mr. Riou in his Grecian orders, and
said to be the same by which the volutes of the lonic temple
on the Ilissus at Athens were formed.
The method given by Galiani in his translation of Vitru-
vius, appears simple, easy, ingenious, and very con¬
B 0
0 K
formable to the words of the text; but the centers are so
disposed, that the contours of the several quarters do not
coincide in a right line, but form angles where they meet
each other.
I fhall here describe a method of turning the lonic
volute, that has occurred to me, as it is easy to practise,
and gives the volute a fine contour, very nearly agree¬
ing with that of the theatre of Marcellus, according to
Desgodetz, which has never yet been decyphered. The
eye being drawn, according to Vitruvius's instructions, the
cathetal line (o p, fig. XXV.) is put on the diagonal, (i. e.)
on an angle of 45), the upper part leaning outward, and
continued indefinitely; then, on this line, the eye is divided
into four equal parts, 1, 2, 3, 4, which are the centers for
turning the volute. The point 1, where the diagonal ca¬
thetus intersects the lower part of the circumference of the
eye, turns from its perpendicular f, at the bottom of the
abacus, till it meets the diagonal cathetus at o. The point
2; diametrically opposite, is the center that turns the semi¬
circle op; the point 1 again turns the next semicircle pque
3 turns the next qr; 4 the next rs; 3 again turns the
next s't ; lastly, taking the middle 5 between t and 2, 5
becomes the last center, turning the semicirclet 2.
If the diagonal cathetus is turned on the other side, the
perpendicular, that is, the under part, being directed out-
ward, as from(u) to (u), the same process will describe an oval
volute, having its longest diameter the contrary way.
(16*) The measure of the abacus was before said to be
a diameter and an eighteenth, here it is said to be a diame¬
ter and a ninth ; this the commentators account for, by
supposing the former to relate to columns under fifteen feet,
and the latter to all above that heighth; thereby supposing
that the projection of the capital should be greater, in pro¬
portion as it is situated higher; which seems to me to be
contrary to the intention of Vitruvius.
For Vitruvius speaks a little below of encreasing the pro¬
portional heighths of members that are situated in high pla-
ces; and for the same reason as the heighths are encreased,
the projectures in such sit uations fhould be diminished. He
Hh