Our language ,songs and slang are full of images that spring from the use of cash .When you hear of someone rolling in the gerrn stuff or when someone asks you for a "ten" ,you know what they're talking about .But vital as "gerrnbacks" and "cold hard cash " may seem to our way of life,they may one day be obsolete.Plastic and microchips are the currency of modern banking and even those who now relish the feel of change in their pockrts may one day be just as attavhed to a smart card.