There are three groups of pottery accepted as existing in North America in the pre-Columbian era. These are the crude stone implements of the nomadic tribes of the Atlantic coast, the earthenware vessels found in the mounds of the Mississippi Valley, and the advanced ceramics of the Pueblo peoples in the Southwest. Though we cannot here discuss the first two varieties, it is worth while, in passing, to note that the Mound Builders left behind them a vast number of pipes for smoking. These were made from a single piece of the hardest procurable stone carved to represent certain birds and animals. Moreover, their pipe sculpture betrays an art so superior to all else that they did that it makes evident how great an importance was probably attached to these pipes. Smoking is an essential preliminary to, and element of, every ritual. Hence it follows, naturally enough, that no one institution, for so it may be called, was more firmly fixed by long usage among the North American Indians, or more characteristic of them than the pipe in all its varied uses and significances.[257] In the arid regions of the Southwest, water was so precious a commodity that the Pueblo peoples very early acquired skill in making receptacles for its transport and conservation and became, as Powell says, “the potters _par excellence_ of aboriginal America.” Just as the first incentive toward the art of pottery grew out of the need of utensils for the preparation of foods, so to-day it is the most general and important motive for its creation. Profoundly influenced by the earlier art of basketry, pottery is always found in close relationship with its sister art wherever the two industries occur together. The nomad tribes would naturally prefer the basket because so much more easily transported from place to place, and they showed extraordinary skill in making cooking vessels of wicker that are not only water-tight but are of such beauty that they are to-day accounted almost priceless by collectors.