_Scientists' Failure to Agree._ It is only fair to say that much of the doubt and indecision on the part of the public is directly attributable to the conflicting statements of our scientists. It should be borne in mind that careful investigation in respect to the relative values of the various forms and sources of lime has been confined largely to the short period of time that has elapsed since recognition of the lime deficiency of our country's soils. Our agricultural literature contained little about soil acidity 20 years ago, and our experiment station tests afford only relatively recent results. Some knowledge of sour soils and the efficacy of lime in their amendment is nearly as old as the history of agriculture, it is true, but answers to the questions uppermost in the minds of men wanting to apply lime to land have been sought only within recent years. The variation in soil types, and in sources of lime, and in preconceived ideas of men drawing conclusions from incomplete data may easily account for failure of our soil scientists to be in the close agreement in statement that would remove all confusion in the public mind. However, the agreement respecting the facts is becoming better assured with every added year of investigation, as a study of station bulletins shows. CHAPTER VII DEFINITIONS _Technical Terms._ The practical man uses a great number of technical terms in his own field of labor, and often fails to recognize the fact that they are technical, and may be puzzling to many other people. He uses such terms for the sake of accuracy, desiring to express to his fellow-workmen exactly what he means. The farmer, stockman, carpenter, banker--all have command of such terms, and need them, but the chemist who, in a way, must come even nearer to accuracy in expression, finds that many people who want his assistance do not care to master and use any of his terms. Failure to do so compels misunderstanding. Anyone who is interested in the right use of lime should be willing to add a few of the chemists' technical terms to the scores in his own line of work that he uses constantly, and thus let the whole matter of liming land come to appear more simple to him. Acquaintance with a few terms is necessary to any understanding of statements of analyses upon which purchase should be made. _An Element_ is a substance that cannot be divided into simpler substances. The number of elements necessary to the growth of plants is small, and of this number calcium is one and magnesium is another.