including large towns and fortified cities, consistent with an urbanized state-level society. Economy Economy in the Vedic period was sustained by a combination of pastoralism and agriculture. There are references, in the Rigveda, to the leveling of fields, seed processing, and storage of grains in large jars. War bounty was also a major source of wealth. Economic exchanges were conducted by gift giving, particularly to kings (bali) and priests (dana), and barter using cattle as a unit of currency. While gold is mentioned in some hymns, there is no indication of the use of coins. Metallurgy is not mentioned in the Rigveda, but the word ayas and instruments made from it such as razors, bangles, axes are mentioned. One verse mentions purification of ayas. Some scholars believe that ayas refers to iron and the words dham and karmara refer to iron-welders. However, philological evidence indicates that ayas in the Rigveda refers only to copper and bronze, while iron or śyāma ayas, literally "black metal", first is mentioned in the post-Rigvedic Atharvaveda, and therefore the Early Vedic Period was a Bronze Age culture whereas the Late Vedic Period was an Iron Age culture. The transition of Vedic society from semi-nomadic life to settled agriculture in the later Vedic age led to an increase in trade and competition for resources. Agriculture dominated the economic activity along the Ganges valley during this period. Agricultural operations grew in complexity and usage of iron implements (krishna–ayas or shyama–ayas, literally black metal or dark metal) increased. Crops of wheat, rice, and barley were cultivated. Surplus production helped to support the centralised kingdoms that were emerging at this time. New crafts and occupations such as carpentry, leather work, tanning, pottery, astrology, jewellery, dying, and winemaking arose. Apart from copper, bronze, and gold, later Vedic texts also mention tin, lead, and silver. Panis in some hymns refers to merchants, in others to stingy people who hid their wealth and did not perform Vedic sacrifices. Some scholars suggest that Panis were semitic traders, but the evidence for this is slim. Professions of warriors, priests, cattle-rearers, farmers, hunters, barbers, vintners and crafts of chariot-making, cart-making, carpentry, metal working, tanning, making of bows, sewing, weaving, making mats of grass and reed are mentioned in the hymns of the Rigveda. Some of these might have needed full-time specialists. There are references to boats and oceans. Book X of the Rigveda refers to