Aristotle, the Greek philosopher, summed up the four chief qualities of money some 2000 years ago. It must be lasting and easy to recognize, to divide, and to carry about. In other words, it must be 'durable, distinct, divisible and portable, When we think of money today, we picture ti either as round, pieces of metal which we call coins, or as printed paper notes are of no use. They will buy nothing and a traveler might starve if he had none of the particular local money' to exchange for food.