covered with tin, and over these stones shall be crampingirons, 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 all of solid stone bound to the buttresses to the height of twenty-four braccia, and thence upwards they shall be constructed of bricks, or of spongite (spugne), as shall be determined on by the masters who build it, they using that which they consider lightest. On the outside a passage or gallery shall be made above the windows, which below shall form a terrace, with an open parapet or balustrade two braccia high, after the manner of those of the lower tribunes, and forming two galleries, one over the other, placed on a richly-decorated cornice, the upper gallery being covered. The rain-water shall be carried off the cupola by means of a marble channel, one-third of an ell broad, the water being discharged at an outlet to be constructed of a hard stone, (pietra forte), beneath the channel. Eight ribs of marble shall be formed on the angles of the external surface of the Cupola, of such thickness as may be requisite; these shall rise to the height of one braccia above the Cupola, with cornices projecting in the manner of a roof, two braccia broad, that the summit may be complete and sufficiently furnished with eaves and channels on every side; and these must have the form of the pyramid, from their base, or point of junction, to their extremity. Thus the Cupola shall be constructed after the method described above, and without framework, to the height of thirty braccia, and from that height upwards it may be continued after such manner as shall be determined
FF
