y of treasures. Donatello soon returned to
Florence, but Filippo pursued his studies with unremitting diligence.
Having exhausted his means, although he lived in the most frugal manner,
he contrived to supply his wants, says Milizia, by pawning his jewels,
but Vasari with greater probability, by setting precious stones for the
goldsmiths, who were his friends. "Nor did he rest," says Vasari, "until
he had drawn every description of fabric--temples, round, square, or
octagon; basilicas, aqueducts, baths, arches, the Colosseum,
amphitheatres, and every church built of bricks, of which he examined
all the modes of binding and clamping, as well as the turning of the
vaults and arches; he took note, likewise, of all the methods used for
uniting the stones, as well as of the means used for securing the
equilibrium and close conjunction of all the parts; and having found
that in all the larger stones there was a hole, formed exactly in the
centre of each on the under side, he discovered that this was for the
insertion of the iron instrument with which the stones are drawn up, and
which is called by us the mason's clamps (_la ulivella_), an invention,
the use of which he restored, and ever afterwards put in practice. The
different orders were next divided by his cares, each order, the Doric,
Ionic, or Corinthian being placed apart; and such was the effect of his
zeal in that study, that he became capable of entirely reconstructing
the city in his imagination, and of beholding Rome as she had been
before she was ruined. But in the year 1407 the air of the place caused
Filippo some slight indisposition, when he was advised by his friends to
try change of air. He consequently returned to Florence, where many
buildings had suffered by his absence, and for these he made many
drawings and gave numerous counsels on his return.

"In the same year an assemblage of architects and engineers was gathered
in Florence, by the Superintendents of the works of Santa Maria del
Fiore, and by the Syndics of the Guild of wool-workers, to consult on
the means by which the cupola might be raised. Among these appeared
Filippo, who gave it as his opinion that the edifice above the roof must
be constructed, not after the design of Arnolfo, but that a frieze,
fifteen braccia high, must be erected, with a large window in each of
its sides: since not only would this take the weight off the piers of
the tribune, but would also permit the cupola itself to be