lead to the attempt to make its surface smooth. This would need to be
effected while the article was still soft; which necessity probably
led to the discovery that ajar of the corrugated or simply coiled type
may be smoothed while still plastic without danger of distortion, no
matter what its size, if supported at the bottom in a basket or other
mold so that it may be shifted or turned about without direct
handling. (See Fig. 526.)

[Illustration: FIG. 526.--Basket-bowl as base-mold for large vessels.]

[Illustration: FIG. 527.--Clay nucleus for a vessel.]

[Illustration: FIG. 528.--Clay nucleus shaped to form the base of a
vessel.]

After this discovery was made, the molding of large vessels was no
longer accomplished by the spiral method exclusively. A lump of clay,
hollowed out (see Fig. 527), was shaped how rudely so ever on the
bottom of the basket or in the hand (see Fig. 528), then placed inside
of a hemispherical basket-bowl and stroked until pressed outward to
conform with the shape, and to project a little above the edges of its
temporary mold, whence it was built up spirally (see Fig. 529) until
the desired form had been attained, after which it was smoothed by
scraping (see Fig. 530).

[Illustration: FIG. 529.--Clay nucleus in base-mold, with beginning
of spiral building.]

[Illustration: FIG. 530.--First form of vessel.]