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manner of the pointed arch, this being a form which displays a rapid
tendency to ascend, and when loaded with the lantern, each part will
help to give stability to the other. The thickness of the vault at the
base must be three braccia and three-quarters; it must then rise in the
form of a pyramid, decreasing from without up to the point where it
closes, and where the lantern has to be placed, and at this junction the
thickness must be one braccia and a quarter. A second vault shall then
be constructed outside the first, to preserve the latter from the rain,
and this must be two braccia and a half thick at the base, also
diminishing proportionally in the form of a pyramid, in such a manner
that the parts shall have their junction at the commencement of the
lantern, as did the other, and at the highest point it must have
two-thirds of the thickness of the base. There must be a buttress at
each angle, which will be eight in all, and between the angles, in the
face of each wall, there shall be two, sixteen in all; and these sixteen
buttresses on the inner and outer side of each wall must each have the
breadth of four braccia at the base. These two vaults, built in the form
of a pyramid, shall rise together in equal proportion to the height of
the round window closed by the lantern. There will thus be constructed
twenty-four buttresses with the said vaults built around, and six strong
high arches of a hard stone (macigno), well clamped and bound with iron
fastenings, which must be covered with tin, and over these stones shall
be cramping irons, by which the vaults shall be bound to the buttresses.
The masonry must be solid, and must leave no vacant space up to the
height of five braccia and a quarter; the buttresses being then
continued, the arches will be separated. The first and second courses
from the base must be strengthened everywhere by long plates of
_macigno_ laid crosswise, in such sort that both vaults of the cupola
shall rest on these stones. Throughout the whole height, at every ninth
braccia there shall be small arches constructed in the vaults between
the buttresses, with strong cramps of oak, whereby the buttresses by
which the inner vault is supported will be bound and strengthened; these
fastenings of oak shall then be covered with plates of iron, on account
of the staircases. The buttresses are all to be built of _macigno_, or
other hard stone, and the walls of the cupola are, in like manner, to be
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