Auctions are public sales of goods, conducted by an officially approved auctioneer. He asked the crowd to gather in the auction room to bid for various items on sale. He encourages buyers to bid higher figures and finally names the highest bidder as the buyer of the goods. This is called 'knocking down' the goods, for the bidding ends when the auctioneer bangs a small hammer on a raised platform. The ancient Romans probably invented sales by auction and the English word comes from the Latin 'autic', meaning 'increase'. The Romans usually sold in this way the spoils taken in war these sales were called 'sub hasta', meaning 'under the spear', a spear being stuck in the ground as a signal for a crowd to gather. In England in the eighteenth and nineteenth centuries goods were often sold 'by the candle' a short candle was lit by the auctioneer and bids could be made while it was burning. Practically all goods can be sold by auction. Among these are coffee, skins, wool, tea, cocoa, furs, fruit, vegetables and wines. Auction sales are also usual for land and property, antique furniture, pictures, rare books, old china and works of art. The auction rooms at Chritie's and Sotheby's in London and New York are world famous. An auction is usually advertised beforehand with full particulars of the articles to be sold and where and when they can be viewed by the buyers. If the advertisement cannot give full details, catalogues are printed, and each group of goods to be sold together, called a 'lot', is usually given a number. The auctioneer need not begin with lot one and continue the numerical order he may wait until he notices the fact that certain buyers are in the room and then produce the lots they are likely to be interested in. The auctioneer's services are paid for in the form. of a percentage of the price the goods are sold for. The auctioneer therefore has a direct interest in pushing up the bidding as high as possible. The auctioneer must know fairly accurately the current market values of the goods he is selling, and he should be acquainted with regular buyers of such goods. He will not waste time by starting the bidding too low. He will also play on the rivalries among his buyers and succeed in getting a high price by encouraging two business competitors to bid against each other. It is largely on his advice that a seller wilt fix a 'reserve' price, that is, a price below which the goods cannot be sold. Even the best auctioneers, however, find it difficult to stop a 'knock-out', whereby dealers illegally arrange beforehand not to bid against each other, but nominate one of themselves as the only bidder, in the hope of buying goods at extremely low prices. If such a 'knockout' comes off, the real auction sale takes place privately afterwards among the dealers. The end of bidding is called 'knocking down' because______.