latter method, known as _pisé_ construction, walls 5 to 7 feet thick were sometimes built. The outer walls of the lowest story were pierced only by small openings, access to the interior being gained by means of ladders, which could be drawn up if necessary, and of a hatchway in the roof. It is possible that some of the elaborate structures of Mexico were developed from such hive-like buildings as those of the typical _pueblos_, the cells increasing in size toward the south, as suggested by Bandelier. Chimneys appear to have been unknown in North America until after contact of the natives with Europeans, the hatchway in the roof serving the double purpose of entrance and flue. Other forms, some 'community' and others not, are the following: The Tlingit, Haida, and some other tribes build substantial rectangular houses, with sides and ends formed of planks, and with the fronts elaborately carved and {47} painted with symbolic figures. Directly in front of the house a totem pole is placed, and near by a memorial pole is erected. These houses are sometimes 40 by 100 feet in the Nootka and Salish regions, and are occupied by a number of families. Formerly some of the Haida houses are said to have been built on platforms supported by posts. Some of these seen by such early navigators as Vancouver were 25 or 30 feet above ground, access being had by notched logs serving as ladders. Among the north-western Indian tribes, as the Nez Percés, the dwelling was a frame of poles covered with rush matting or with buffalo or elk skins. The houses of the Californian tribes were rectangular or circular; of the latter, some were conical, others dome-shaped. There was also formerly in use in various parts of California, and to some extent on the interior plateaus, a semi-subterranean earth-covered lodge known amongst the Maidu as _kum_. The most primitive abodes were those of the Paiute and the Cocopa, consisting simply of brush shelters for summer, and for winter of a framework of poles bent together at the top and covered with brush, bark, and earth. Somewhat similar structures are erected by the Pueblos as farm shelters, and more elaborate houses of the same general type are built by the Apache of Arizona. As indicated by archæological researches, the circular wigwam, with sides of bark or mats, built over a shallow excavation in the soil, and with earth thrown against the base, appears to have been the usual form of dwelling in the Ohio valley and the immediate valley of the Mississippi in prehistoric and early historic times. Another kind of dwelling, in use in Arkansas before the Discovery, was a rectangular structure with two rooms in front and one in the rear; the walls were of upright posts thickly plastered with clay on a sort of {48} wattle. With the exception of the _pueblo_ structures, buildings of stone or adobe were unknown until recent times. The dwellings of some of the tribes of the plains, such as the Sioux, Arapaho, Comanche,