The communal household and the political structure built upon it, as above described in the case of the Iroquois, seem to have existed all over ancient North America, with agreement in fundamental characteristics and variation in details and degree of development. There are many corners as yet imperfectly explored, but hitherto, in so far as research has been rewarded with information, it all points in the same general direction. Among the tribes above enumerated as either in savagery or in the lower status of barbarism, so far as they have been studied, there seems to be a general agreement, as to the looseness of the marriage tie the clan with descent in the female line, the phratry, the tribe, the officers and councils, the social equality, the community in goods (with exceptions already noted), and the wigwam or house adapted to communal living. [Illustration: View, Cross-section, and Ground-plan of Mandan round house.] [Sidenote: Circular houses of the Mandans.] The extreme of variation consistent with adherence to the common principle was to be found in the shape and material of the houses. Those of the savage tribes were but sorry huts. The long house was used by the Powhatans and other Algonquin tribes. The other most highly developed type may be illustrated by the circular frame-houses of the Mandans.[85] These houses were from forty to sixty feet in diameter. A dozen or more posts, each about eight inches in diameter, were set in the ground, "at equal distances in the circumference of a circle, and rising about six feet above the level of the floor." The tops of the posts were connected by horizontal stringers; and outside each post a slanting wooden brace sunk in the ground about four feet distant served as a firm support to the structure. The spaces between these braces were filled by tall wooden slabs, set with the same slant and resting against the stringers. Thus the framework of the outer wall was completed. To support the roof four posts were set in the ground about ten feet apart in the form of a square, near the centre of the building. They were from twelve to fifteen feet in height, and were connected at the top by four stringers forming a square. The rafters rested upon these stringers and upon the top of the circular wall below. The rafters were covered with willow matting, and upon this was spread a layer of prairie grass. Then both wall and roof, from the ground up to the summit, were covered with earth, solid and hard, to a thickness of at least two feet. The rafters projected above the square framework at the summit, so as to leave a circular opening in the centre about four feet in diameter. This hole let in a little light, and let out some of the smoke from the fire which blazed underneath in a fire-pit lined with stone slabs set on edge. The only other aperture for light was the doorway, which was a kind of vestibule or passage some ten feet in length. Curtains of buffalo robes did duty instead of doors.