Maria del Fiore in Florence, the difficulties of which were such that after the death of Arnolfo Lapi there had been no one courageous enough to think of raising it without vast expenditure for a wooden framework. Yet he did not impart this his invention to Donato or to any living soul, nor did he rest in Rome till he had considered all the difficulties connected with the Ritonda, wondering how the vaulting was raised. He had noted and drawn all the ancient vaults, and was for ever studying them; and if peradventure they had found pieces of capitals, columns, cornices, and bases of buildings buried underground, they would set to work and have them dug out, in order to examine them thoroughly. Wherefore a rumour spread through Rome, as they passed through the streets, going about carelessly dressed, so that they were called the "treasure-seekers," people believing that they were persons who studied geomancy in order to discover treasure; and this was because they had one day found an ancient earthenware vase full of medals. Filippo ran short of money and contrived to make this good by setting jewels of price for certain goldsmiths who were his friends; and thus he was left alone in Rome, for Donato returned to Florence, while he, with greater industry and labour than before, was for ever investigating the ruins of those buildings. Nor did he rest until he had drawn every sort of building--round, square, and octagonal temples, basilicas, aqueducts, baths, arches, colossea, amphitheatres, and every temple built of bricks, from which he copied the methods of binding and of clamping with ties, and also of encircling vaults with them; and he noted the ways of making buildings secure by binding the stones together, by iron bars, and by dove-tailing; and, discovering a hole hollowed out under the middle of each great stone, he found that this was meant to hold the iron instrument, which is called by us the ulivella,[18] wherewith the stones are drawn up; and this he reintroduced and brought into use afterwards. He then distinguished the different Orders one from another--Doric, Ionic, and Corinthian; and so zealous was his study that his intellect became very well able to see Rome, in imagination, as she was when she was not in ruins. In the year 1407 the air of that city gave Filippo a slight indisposition, wherefore, being advised by his friends to try a change of air, he returned to Florence. There many buildings had suffered by reason of his absence; and for these, on his arrival, he gave many designs and much advice. [Footnote 18: This was probably something like the modern lewis.]