“He returned, therefore, to his house, and stated his whole purpose on a sheet of paper, as clearly as he could possibly express it, when it was given to the tribunal in the following terms:—­’The difficulties of this erection being well considered, magnificent signors and wardens, I find that it cannot by any means be constructed in a perfect circle, since the extent of the upper part, where the lantern has to be placed, would be so vast, that when a weight was laid thereon, it would soon give way.  Now it appears to me that those architects who do not aim at giving perpetual duration to their fabrics, cannot have any regard for the durability of the memorial, nor do they even know what they are doing.  I have therefore determined to turn the inner part of this vault in angles, according to the form of the walls, adopting the proportions and 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