584 SELECTIONS FROM ADDRESSES. 



these common ingredients. Iodine, for example, is an exceed- 

 ingly precious medicinal article, which is manufactured from 

 the incineration of sponge and other vegetables growing on the 

 sea-shore. It would be perfectly useless to try to abstract 

 iodine from plants grown away from the salt water of the 

 ocean, which always shows this ingredient on being tested, but 

 no more vain than it is to try to raise wheat from a soil which 

 gives, on testing, no phosphates. 



Of these dozen or fourteen elements, necessary to the forma- 

 tion of the ordinary edible vegetable products, silica, or silex, 

 or flint makes up the larger proportion in most kinds of rocks, 

 and consequently in most kinds of soils. A fair proportion of 

 this article would be anywhere from thirty to seventy per 

 centum, although some soils are capable of supporting some 

 vegetables with a vastly higher ratio of pure silex. The arundo 

 arenaria, a species of reed grass, which has proved of the 

 utmost value in political economy, by its aid in reclaiming 

 millions of acres of movable sands on the western coasts of 

 France, and even on our own cape, by its roots binding the 

 loose and blowing sands, is sustained in perfection where more 

 than ninety per centum of its soil is pure flint. 



Next after silex, is alumina, the basis of clay soils ; then 

 come lime, magnesia, soda, various acids and some oxides or 

 rusts of metals. Let us give an illustration of the relative pro- 

 portions of these in an ordinarily fertile soil, or one which will 

 produce good fair crops without the addition of manures. 

 Such a soil might be expected to present in every thousand 

 pounds in weight, a hundred pounds of organic matters ; six or 

 seven hundred of silex ; fifty or sixty of lime, and the same of 

 alumina, and from two to eight pounds each of potash, soda 

 and magnesia; forty pounds of carbonic acid and two to four 

 pounds each of phosphoric and sulphuric acids. And as be- 

 fore suggested, it is just as fatal, so far .as specific plants are 

 concerned, to leave out the one as the other of the various 

 components. 



The question will naturally be asked, " Where do such in- 

 gredients as potash, soda, and oil of vitriol, drugs we know in 

 every day experience as the costly, corrosive and strongly 

 marked articles of the apothecaries' shelves, come from ?" The 

 reply is easy, for their whereabouts in the soil is one of the 



