Wheeled transport by wagon or cart was the typical mode in barbarian Europe. The wheel was invented in Mesopotamia prior to 3000 B.C. Its use spread across Europe by 2500 B.C. (Fig. 12-10). Early wheels were solid, either of one piece of wood or discs made from planks. There were two forms of vehicles, the two-wheeled cart and the wagon with four wheels. There is also archaeological evidence of corduroy roads of logs built as early as 2500 B.C. The use of wheeled vehicles required proper terrain, not too hilly or boggy. Central and northern Europe possessed these qualities, with the result that wheeled vehicles aided the frequent moves of the peasant farmers. Another aspect was the associated rise in importance of draft animals, both oxen and horses with their harness trappings. In Celtic times there was a shift from the heavier wagons to the lighter two-wheeled war chariots. After 500 B.C. the typical warrior or chief's grave includes the chariot. The appearance of spokes likely derives from the need for lighter, faster chariots. Spoked wheels are a common Celtic trait dating from the last few centuries B.C.
The gauge of wagons, the distance between the wheels, was established at 3 feet 6 inches to 3 feet 9 inches; a tradition that extends from the time of Ur in Mesopotamia down to the Hallstadt wagons of the fifth and sixth centuries B.C. The later La Tene wagons shifted to a gauge of 4 feet 8 V 2 inches which is the standard railroad gauge still in use today. Archaeological evidence for these gauges is provided by wheel ruts preserved in numerous European sites. In northern Europe we have a continuation in use of the vehicles developed in earlier periods—the sledge, wooden dugout, and skis (Fig. 12-11).