r-jar chanced to be
modeled in one of the convex-bottom bread-baskets (see Fig. 539), it
would become necessary, on account of the thickness of these wicker
bowls, to remove the form from the mold before it dried. By absorption
it would dry so rapidly that it would crack, especially in contracting
against the convexity in the center of the basket-bottom. (See Fig.
539, _a_.) In order that this form might be supported in an upright
position until dry, it would naturally be placed on one of the
wicker-rings. Moreover, that the bottom might not sink down or fall
out, a wad of some soft substance would be placed within the ring.
(See Fig. 540, _a_.) As a consequence the weight of the plastic vessel
would press the still soft bottom against the central wad, (Fig. 540,
_a_) and the wicker ring (Fig. 540, _c_) sufficiently to cause the
rounding upward of the cavity (Fig. 540, _b_) first made by the
convex-bottom of the basket-mold, as well as form the encircling
indentation (Fig. 540, _c_). Thus by accident, probably, only possibly
by intention, was evolved the most useful and distinctive feature of
the modern water-jar or olla, the _concave bottom_. This, once
produced, would be held to be peculiarly convenient, dispensing with
the use of a troublesome auxiliary. Its reproduction would present
grave difficulties unless the bottom of the first vessel, thickly
coated with sand to prevent cracking, was employed as a mold, instead
of the absorbent convex-centered basket-bowl.

[Illustration: FIG. 539.--Section of incipient vessel in basket-mold.]

[Illustration: FIG. 540.--Section of vessel supported for drying.]

I infer this because, to-day, a Zuni woman is quite at a loss how to
hollow the bottom of a water-jar if she does not possess a form or
mold made from the base of some previously broken jar of the same
type. She therefore, carefully preserves these precious bottoms of her
broken ollas, even cementing together fractured ones, when not too
badly shivered, with a mixture of pitch or mineral asphaltum and sand.
I have seen as many as a dozen or more of these molds (see Fig. 541)
in a single store room.

[Illustration: FIG. 541.--Base-mold (bottom of water-jar).]

As the practice of molding all new vessels of this class in the
bottoms of older ones was general--I might say invariable--any
peculiarities of form in the originals must have been communicated to
those ensuing; from the latter to others, and so on, though in