But these two architects had not much experience in laying foundations in Pisa, and since they did not drive in piles as they should have done, before they were half through the work, there was a subsidence on one side, and the building leant over on its weaker side, so that the campanile hangs 6-1/2 braccia out of the straight according to the subsidence on that side, and although this appears slight from below, it is very apparent above, so that one is filled with amazement that the tower can stand thus without falling and without the walls being cracked. The reason is that the building is round both within and without, and the stones are so arranged and bound together, that its fall is all but impossible, and it is supported moreover by foundations raised 3 braccia above the ground level, which were made to maintain it after the subsidence had taken place, as may be seen. Had it been square; I am convinced that it would not be standing, to-day, as the corners of the square would have pushed out the sides so that they would have fallen, a thing which frequently happens. And if the Carisenda tower at Bologna, which is square, leans without falling, that is because it is lighter and does not hang over so much, nor is it nearly so heavy a structure as this campanile, which is praised, not because of its design or good style, but simply by reason of its extraordinary position, since to a spectator it does not appear possible that it can remain standing. The Bonanno mentioned above, while he was engaged on the campanile, also executed in 1180 the principal door of the Duomo of Pisa in bronze. On it may be seen these words: _Ego Bonannus Pis, mea arle hanc portam uno anno perfeci tempore Benedicti operarii._ That the art was making steady progress may be seen by the walls of S. Giovanni Lateran at Rome, which were constructed of the spoils of antiquity under Popes Lucius III. and Urban III., when the Emperor Frederick was crowned by the latter, because certain small temples and chapels there, made with these spoils, possess considerable merit of design and contain some things which are worth notice, and this, among others, that the vaults were made of small tubes with compartments of stucco, so as not to overload the side walls of the buildings, a very praiseworthy contrivance for those times. The cornices and other parts show that the artists were helping one another to find the good.