18 STATE BOARD OF AGRICULTURE. 



that "the constant dropping of water will wear away a stone." If we 

 say ''will dissolve a stone," thus seeming to wear it away, we shall 

 get nearer scientific accuracy. This constant action of carbonic acid, 

 ''at noon of day and noon of night," is one of the agencies which has 

 greatly modilied the condition of the surface of our globe. The im- 

 portance of a supply of humus in the soil as a constant source of this 

 persistent acid has possibly been overlooked. 



The humus itself has strong solvent powers, especially for the in- 

 soluble phosphates. The influence of oxygen in converting the metallic 

 sulphides to sulphates and ferrous oxide to ferric compounds, thus 

 breaking up the molecular structure of some of the hardest rocks, is 

 too well recognized to need elucidation before this audience. 



The uses of the minute organisms in the soil in elaborating plant food 

 will probably be discussed by Prof. Marshall. The process of nitrifica- 

 tion is still a matter of great importance in agriculture, even if the nitre 

 plantations have become matters of history in consequence of the dis 

 covery of nitrate of soda in Chili. Nature is not crowded out of her 

 normal field of work by discovery of temporary supplies in some 

 province of her wide domain. She still works her continental nitre 

 beds under favorable conditions, even if man forgets it in the discovery 

 of a pocket of Chili nitre. Her mighty plan still moves on, forgetful 

 of the forgetfulness of man. The wise farmer will seek to avail himself 

 of her benefits, even if not quotable on boards of trade. 



THE ACTIVE AND THE MECHANICAL ELEMENTS OF THE SOIL. 



The relatively small per cent of active elements in the soil and the 

 very large amount of mechanical elements attracted your notice. When 

 we find that some of these materials do not enter into the structure 

 of agricultural crops, or only in very small proportion, the question 

 arises, Are they of any benefit? Take clay for example, a silicate 

 of alumina, the aluminous material forming no part of any cultivated 

 plant. The oxide of iron, while a necessary constituent of all chloro- 

 phyllous or leaf plants, is found in our soils in great abundance above 

 all' requirements of plants. Yet these materials, reinforced by the lime 

 and magnesia in the soil, have a wonderful power of fixing in relatively 

 insoluble form the materials for plant food that are readily soluble in 

 pure "water. 



If we filter a solution of nitrate of potash through garden soil, the 

 water that filters through will contain nitrate of lime, leaving the potash 

 in the soil. If chloride of ammonium is treated in the same way, the 

 ammonia is left in the soil and chloride of calcium is found in the filtrate. 

 Thus the oxide of iron found in the soil and the clay are found to con- 

 tain ammonia. A permeable soil is not necessarily a leachy soil. The 

 cheap and abundant compounds of lime and magnesia are washed away 

 in the drainage water, while the precious potash, phosphates and am- 

 monia are retained in the soil. The great loss is nitrate, and the quantity 

 is enormous. The Rhine daily discharges nitrates equivalent to 270 tons 

 of nitrate of potash; the Nile, 1,100 tons, and the Mississippi 2,000 tons. 

 How stop this enormous waste? The green withes did not suffice to bind 

 the limbs of Sampson, but green growing crops will arrest the fugitive 

 nitrates and hold them for use of man and beast by the halter of veg- 

 etable growth. 



