"That was tested," said Percy. "The green manure alone increased the average yield to only fourteen bushels while the green manure and limestone together raised the average wheat yield to nineteen bushels, the further increase to twenty-seven bushels having been produced by the addition of phosphorus." "Well, Sir," said the Chief, "we have made both extensive intensive investigations concerning the chemistry of the soil solution by very delicate and sensitive methods of analysis we have developed, and we have also conducted culture experiments for twenty-day periods with wheat seedlings in the water extract of soils from all parts of the United States, and the results we have obtained have changed the thought of the world as to the cause of the infertility of soils." "But you have not made analyses for total plant food in the soils or conducted actual field experiments with crops grown to maturity?" asked Percy. "No, we have not done that," answered the Chief. "Those are old methods of investigation which have been tried for many years and yet no chemist can tell in advance what will be the effect of a given fertilizer upon a given crop on a given soil." "That is true," said Percy, "but neither can any merchant tell in advance just what effect will be produced on the next day's business by the addition of a given number of a given kind of shoes to a given stock on his shelves. There are many factors involved in both cases." "Yes, you are right in that," said the Chief, "we are just beginning to understand the chemistry of the soil, and we hope soon to have very complete proof of the advanced ideas we already have concerning the causes of the fertility and infertility of soils." "Referring to the specific case of the Leonardtown loam of Maryland," said Percy, "I find the following statement on page 33 of the Report of the Field Operations of the Bureau of Soils for 1900. After describing the Norfolk loam of St. Mary County, the writer says: "'The Leonardtown loam is a very much heavier type of soil. It covers about forty-one per cent. of St. Mary County. The soil is a yellow silty soil, resembling loess in texture, underlaid by a clay subsoil with layers or pockets of sand. This soil has been cultivated for upward of two hundred years, but it is now little valued and is covered with oak and pine over much of its area. It is worth from $1 to $3 per acre. The cultivated areas produce small crops of corn, wheat, and an inferior grade of tobacco.'"