Matthews's description of the caches prepared by the tribes with whom he was so closely associated is most interesting, and it tends to explain the origin and use of the numerous pits often discovered in the vicinity of ancient village sites east of the Mississippi. He wrote: "The numerous _caches_, or pits, for storing grain, are noteworthy objects in the village. In summer, when they are not in use, they are often left open, or are carelessly covered, and may entrap the unwary stroller. When these Indians have harvested their crops, and before they start on their winter-hunt, they dig their _caches_, or clear out those dug in previous years. A _cache_ is a cellar, usually round, with a small opening above, barely large enough to allow a person to descend; when finished, it looks much like an ordinary round cistern. Reserving a small portion of corn, dried squash, etc., for winter use, they deposit the remainder in these subterranean store-houses, along with household-utensils, and other articles of value which they wish to leave behind. They then fill up the orifices with earth, which they trample down and rake over; thus obliterating every trace of the excavation. Some _caches_ are made under the floors of the houses, others outside, in various parts of the village-grounds; in each case, the distance and direction from some door, post, bedstead, fire-place, or other object is noted, so that the stores may be found on the return of the owners in the spring. Should an enemy enter the village while it is temporarily deserted, the goods are safe from fire and theft. This method of secreting property has been in use among many tribes, has been adopted by whites living on the plains, and is referred to in the works of many travelers." (Op. cit., pp. 8-9.) Such were the characteristic features of the Hidatsa villages. CROWS. Before the separation of the Crows from the Hidatsa they may have occupied permanent villages of earth-covered lodges, such as the latter continued to erect and use until very recent years. But after the separation the Crows moved into the mountains, the region drained by the upper tributaries of the Missouri, and there no longer built permanent structures but adopted the skin tipi, so easily erected and transported from place to place. Many of their tipis were very large, beautifully made and decorated, and were evidently not surpassed in any manner by the similar structures constructed by other tribes of the Upper Missouri Valley.