I. General characteristics of the potash industry, 31.— II. The industry's demand curve: relationship between potash prices and mixed fertilizer prices, 32; elasticity of the demand for fertilizer, 34; elasticity of the demand for potash, 42. — III. Nature of the supply: few sellers, 43; formally free entry, 43; no exit from the industry without loss, 47. — IV. History of potash prices in the United States: base prices (prices at the ports), 48; the basing point system of pricing, 53. — V. The individual demand curve, 55. — VI. The effects of oligopoly: profits and expanding capacity, 60. — VII. Conclusions, 67.