The Amerinds, though not always engaged in war, were always on the defensive against stronger tribes whose warriors might appear on the scene. These stronger tribes were not necessarily Amerinds of a different stock or strangers; often, as in the South-west, defensive works were erected against relatives as much as against different tribes, just as we, in our time, have had three wars that were not with another race. In New Mexico the villages, besides being built on the communal principle, were often surrounded by a defensive wall. Such a wall can still be traced around the ruins of Pecos, as well as in parts at other ruins. The hill-forts of the Ohio kind were undoubtedly the result of circumstances similar to those that prevailed in the South-west: a desire to combine as closely as possible defence and the cultivation of the soil. They were often interdependent. If conditions changed, or a tribe grew strong enough to dominate the situation, the defences might be abandoned. These works do not necessarily imply that their builders were defeated and driven back by wilder tribes. They indicate only that the builders felt defensive works necessary at the time of the building; their circumstances then demanded them. They do not indicate difference in race or remote origin. The constructors were Amerinds, though not all one stock. There were tribes of different stocks in the Mississippi valley all the time, just as there were in other parts of the land, and the attempt that has been made by some writers to establish the idea that the Mississippi valley was once occupied by a single mysterious race that was overpowered and driven out or exterminated by the “Indians” has no good foundation.