Advances in the economy were obviously present in the fully developed Middle phase. The Union County flint “mines” and workshops were intensively worked. Trade with the Lake Superior, lower Atlantic and Gulf Coast regions was resumed. Chief imports of raw materials were copper and marine shells, Busycon, Marginella, Oliva and Olivella. Art, while possibly as highly developed as Hopewellian, resulted in a far smaller number of art objects in fewer durable media. Intaglio rock carvings (chiefly in southern Illinois) of geometric designs, human hands, ceremonial paraphernalia, animal outlines, and, in a few instances, painted hollowed-out animal silhouettes can probably be ascribed to this period on the basis of the symbols employed. Dwellings or cabins were relatively substantial structures and the extent of village remains indicate a large general population as compared to earlier times in the state. Trade and art suggest leisure and wealth or surplus available for exchange or to support officials and others in non-food productive pursuits. This prosperity was possibly due to newly discovered methods of intensive cultivation of maize and possibly to a greater diversity of crops than ever before. [Illustration: Fig. 25. Carved stone pipe (fragmentary) from Kingston Lake Site (Cahokia subculture, Middle Mississippi period). Owned by Donald Wray. Right-hand figure shows the pipe reconstructed.] Territorially the tribe probably consisted of a number of villages and the surrounding country. Each tribe may have had a chief village or capital that was also a religious center with tribal (public) buildings and a temple. Archaeological and historical evidence shows that these buildings, presumably temples and the dwellings of tribal chiefs and the high priests, were erected on the flat tops of rectangular earthen mounds or pyramids, which were grouped around a plaza of ceremonial square. Here the tribe gathered for religious and political ceremonies and for important funerals. Intertribal negotiations and chunkey games were probably also staged on or near the plaza. Pipes, either of stone or pottery, were generally of the “equal-armed” type (where stem length is about equal to bowl height). In numerous instances, a short projection resembling the stem in shape but shorter, extends beyond the bowl away from the smoker. Massive effigy pipes of stone were widespread but not numerous. Some were excellently carved. From their construction, it is obvious that they were made to be smoked through a reed or hollow wooden stem called in later times the calumet. These together probably constituted a form of ceremonial pipe that served as a safe conduct between tribes, as a bond and signature at peace- and treaty-making ceremonies, and to present tobacco smoke as incense to the gods in religious rituals.