252 SELECTIONS FROM ADDRESSES. 



soils are adapted to particular crops, and has perhaps been told 

 that this depends upon the fact, that some chemical compound 

 is present or absent in such soils. He has heard it assigned as 

 a reason, why the grasses soon tire if kept without change in 

 one soil, that they exhaust the alkaline silicates more rapidly 

 than, in the process of decomposition or of manuring, they are 

 afforded to the soil. Phosphates of lime and magnesia, and nit- 

 rogenized bodies, are mentioned as indispensable to the grain 

 crops. But what are silicates, and phosphates, and nitrogen 

 compounds, but terms of ignorance, to the uninitiated? Neither 

 their composition nor properties can be understood, without the 

 fundamental information of which we are speaking. What the 

 practical man wants, is to be carried clear back of words to 

 things, — behind compounds, to elements. These, for once in 

 his life, at least, he should be permitted to see face to face. He 

 ought to know whether they are solid, liquid, or aeriform ; what 

 is their color, density, and other sensible properties : and more 

 especially, what friendships they have for one another ; by what 

 laws they build themselves up into compounds ; and by what 

 rules these, again, transform themselves into still other combi- 

 nations, or split into their primitive elements. 



But, leaving the composition of the solid earth, and the living 

 beings it supports, what, let us inquire, is known concerning the 

 air, that transparent medium in which we live, and move, and 

 have our being ? How far is its actual weight appreciated, what 

 is known of its power of commingling with other gases, of dis- 

 solving liquids and even solids themselves? Who realizes that 

 the air, in invariable proportions, is made up essentially of two 

 elements, as diverse in nature as charcoal and sulphur ? How 

 few are aware, that it is ever suffering important changes from 

 the burning of combustibles and the breathing of animals ; and 

 that these changes would be fatal to ourselves, unless corrected 

 by the respiration of plants ! Notwithstanding much is said 

 about the atmosphere, about good and bad air, and airs dry and 

 wet, hot and cold, very few are the persons who are rationally 

 convinced of the nature of that deterioration which takes place 

 in an atmosphere that has sustained the combustion of ordinary 

 fuel or lights. Few, very few, are the persons who practically 



