Barter, or Truck, is the ex-? changing of one commodity for another ; and forms a rule in the commercial part of arithmetic, by which the commodities are properly calculated and equalled, by computing the respective value of the different articles offered for exchange.

The proper way of ascertaining the difference of prices in barter would be, to find the price of one of the commodities, and an equivalent quantity of the other, either by practice, or by the rule of three.