A constant width for the dado is also common to all the orders in that it
always lines up with the projection of column bases. This projection is the same for
all the orders, as was established in the third chapter and as will be further explained
in what follows.
PERRAULT
82 Chapter VIII
The Diminution and Enlargement of Columns
TJLn.HE TWO most important requirements
in architecture are durability and the appearance of durability, which, as we have
already said, produce one of the principal constituents of beauty in buildings. All
architects have made columns more slender at the top than at the bottom, and this
is what we call diminution. Some have made them a little thicker near the middle
than at the bottom, and this is what is called enlargement [enflement}?2
Vitruvius would have the diminution of columns vary according to their
height in feet and not according to their height in modules. Accordingly, a column
of fifteen feet must be diminished by the sixth part of the diameter at its base and
one of fifty feet by only one eighth. For other columns of medium height, he makes
the diminution proportional. But we find that these rules have not been observed at
all in antiquity. The diminution of the columns of the Temple of Peace and of the
portico of the Pantheon, of the Roman Forum, called the Campo Vaccino, and of the
Basilica of Antoninus does not differ at all from the diminution of the columns of
the Temple of Bacchus, which are only one quarter the height of the others. There
are even some very large ones, such as those of the Temple of Faustina, of the Portico
of Septimius, of the Temple of Concord, and of the Baths of Diocletian, whose diminution is greater than that of others that are half their size, such as those of the Arches
of Titus, Septimius, and Constantine. In fact, these small columns, which are less
than fifteen feet high, have a smaller diminution than the sixth part that Vitruvius
gives them, since they diminish by only about a seventh part and one half. Furthermore, even in the largest, although they exceed the fifty feet of Vitruvius, we find a
greater diminution than that prescribed for them, for they also diminish by as much
as a seventh part and one half, instead of by only one eighth, as they should according
to Vitruvius's rule.
Nor are the differences between the orders what determine variations in
diminution, since both small and large diminutions are present in various works of
all the orders. The Tuscan column must be excepted, however, since Vitruvius gives
it a diminution as large as a fourth part. Nevertheless, some Moderns have not followed Vitruvius in this, and Vignola gives it a diminution of only one fifth. In Trajan's Column, the only Tuscan work remaining from antiquity, the diminution, being
only a ninth part, is much smaller still. Therefore, in order to maintain a mean between these extremes, I give the Tuscan column a diminution of a sixth part, rather
PART ONE: THINGS COMMON TO ALL THE ORDERS
than only a seventh part and one half, which the columns of the other four orders
have. It would appear reasonable, were diminution to be altered according to the
orders, to make diminution less rather than more in orders where columns are shortest
in proportion to their thickness, because it is in these that diminution is most apparent. Nevertheless, since the diminution that Vitruvius gives the Tuscan column
has been followed by most architects, I believe that deference to custom,33
which is
one of the chief laws of architecture, demands that this diminution be somewhat
increased in the Tuscan Order.
I have put in the following table the different dimensions of the various
orders, together with their diminutions, in order to show by these examples that the
Ancients varied diminution neither according to the different orders nor according to
different column heights. Diminutions vary within the same order and for the same
column height and, moreover, are the same in different orders and for different column heights. One may see in the table, for example, that the Doric column of the
Theater of Marcellus and the Doric column of the Colosseum, which are about the
same height, have very different diminutions, one being twelve minutes, the other
four, and that the Ionic column of the Temple of Fortuna Virilis and that of the
Colosseum, which are also the same height, have divergent diminutions of seven and
ten minutes respectively. On the other hand, in the column of the Temple of Fortuna
Virilis and in that of the Portico of Septimius the diminution is the same, although
the former, which is Ionic, measures only twenty-two feet and the latter, which is
Corinthian, measures as much as thirty-seven feet.
Now of all the diminutions that have been given to all columns, examples
of which are listed in the table, I have taken the mean, adding the size of the smallest
diminution to the size of the largest and taking half of their sum, which comes to
about eight minutes. If we add the size of the smallest diminution, which is that of
the Doric column of the Colosseum at only four and one-half minutes, to the size of
the largest, which is that of the Doric of the Theater of Marcellus at as much as
twelve, half of these sizes, which together make sixteen and one half, is eight and
one quarter. Similarly, if we add the size of the smallest diminution of the columns
that remain, which is six and one eighth in the column of the Basilica of Antoninus,
to the largest of ten and one half in the column of the Temple of Concord, half of
these two sizes, which together make sixteen and five eighths, is eight and five sixteenths. Now this dimension of eight minutes, which makes almost exactly a seventh
part and one half of the diameter, is one fifth of my small module, or four minutes,
taken from either side of the column. I have not listed the diminutions of the Moderns
because they are the same as those of antiquity, which vary from author to author and
from order to order.
83
PERRAULT
84 TABLE OF THE DIMINUTION OF COLUMNS
Height Diameter Diminution
of Shaft
feet inches feet inches minutes
Theater of Marcellus 21 0-0 3 0-0 12-0
Doric
Colosseum 22 lo-V-z 2 8-Y4 4-'/a
Temple of Concord 36 0-0 4 2-'/2 io-Y2
Ionic Temple of Fortuna Virilis 22 IO-O 2 II-O 7-Y2
Colosseum 23 o-o 2 8-3/4 I O-O
Temple of Peace 49
6
3- 5 8-0 6-