_Compound association._—A still closer association, sometimes called compound association, is found where several workers combine efforts of different kinds in a single finished product. It is easily illustrated in an ordinary dairy, where one of the family drives up the cows, another does the milking, another sets the milk and cares for the purity of all utensils, another perhaps skims the milk and churns the butter, and still another works and packs it. All this labor of many hands has its importance represented in the butter packed for use. The particular advantages of this division of labor will be treated in a future chapter. _Aggregation of forces._—A still further advance in association appears when many laborers in many ways, with multitudes of tools and machinery, are combined in a huge establishment in such a way as to employ all efficiently. This is illustrated in the so-called bonanza farms of the west, but more distinctly appears in the great manufactories, or in any extensive coöperation or great enterprise. A study of these will also require a future chapter. While all these methods of association blend with and into each other in every kind of community, a careful analysis of each is necessary to a full understanding of their relation to welfare. For this reason it is best to analyze and illustrate each by itself. The succeeding chapters will take up all the intricacies of exchange before presenting the special advantages and disadvantages of technical division of labor and of great corporations. Chapter VIII. Exchange: Advantages, Limitations And Tendencies. _Exchange in production._—The immense importance of exchange in promoting the welfare of communities is easily granted, and is illustrated in every village store or even in every simple farming community. Today the market for farm products is easily felt to be the most important consideration, and weighs in every farmer’s mind when buying or selling his farm. When a state like Kansas raises from six to ten times as much wheat as its people can use, exchange is evidently an essential factor in every farmer’s welfare.