83．An auction is usually advertised beforehand with full particulars of the articles to be sold and where and when they can be viewed by potential 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 I and continue in the order of numbers: 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.