Value of chemical analysis 539 Interpretation of chemical analysis 539 Nitrogen 540 Phosphoric acid 541 Importance of mechanical condition of phosphate 542 Potash 542 Other items in the chemical analysis of manures 543 Fertilisers and Feeding Stuffs Act 543 Different methods of valuing manures 544 Unit value of manurial ingredients 544 Intrinsic value of manures 545 Field experiments 545 Educational value of field experiments 547 Value of manures deduced from experiments 548 Value of unexhausted manures 549 Potential fertility of a soil 549 Tables of value of unexhausted manures. 551 APPENDIX TO CHAPTER XXV. NOTE I. Factors for calculating compounds from manurial ingredients 553 II. Units for determining commercial value of manures and cash prices of manures 554, 555 III. Manurial value of nitrogen and potash in different substances 556 IV. Comparative manurial value of different forms of nitrogen and potash 557 V. Lawes' and Gilbert's tables for calculating unexhausted value of manures 559 CHAPTER XXVI.--THE ROTHAMSTED EXPERIMENTS. Nature of experiments on crops and manures 561 Soil of Rothamsted 561 Table I. List of Rothamsted field experiments 562 Wheat experiments-- Unmanured plots 562 Wheat grown continuously on same land (unmanured) 562 Table II. Results of first eight years 562 Table III. Results of subsequent forty years 562 Table IV. Wheat grown continuously with farmyard manure (14 tons per annum) 564