SECRETARY'S REPORT. 109 



organic contents of furnishing a continual supply'of this most 

 vahiable form of the food of plants. 



Observe further, that not only does the carbonic acid, thus 

 distributed throughout such rich vegetable loams, convey 

 directly its important nutritious matter to the growing plant, 

 but it is the most powerful solvent which nature furnishesus, under 

 these conditions, for the calcareous compounds, and for the 

 various alkaline compounds contained in the granules of sub- 

 divided rocks ; so that the water passed through such soil 

 becomes freighted with carbonic acid, and thus has a powerful 

 dissolving action which it did not possess when it descended in 

 the form of rain to strike upon the surface of the ground. All 

 these various conditions, then, require to be taken into account, 

 and they must be in each particular case precisely determined, 

 otherwise we have not the facts. But when we do obtain all 

 the facts, then we are in a condition well prepared to reason 

 upon them, and to deduce our general laws and our practical 

 rules, suggested by those generalizations. 



But, further than this : this knowledge of the soil, this terra 

 Jirma of the science and practice of agriculture does not consti- 

 tute its whole. We have to deal in agriculture, as we all know, 

 with living beings. We have all the physiological la'ws relating 

 to their development and growth, their nutrition and various 

 functions, to consider. We have in agriculture much of the 

 mystery, much of the difficulty and complication in our problems 

 which belong to the practice of the physician. We have added 

 to the requisitions of the most profound chemical analysis and 

 the largest generalizations in chemical science, a demand for 

 the facts and laws that belong to physiology, embracing all that 

 is known of the functions of living beings, in their relations to 

 external agencies of a chemical and mechanical nature. What 

 wonder, then, is it, that agriculture (pardon me for saying it,) 

 is a science still in its infancy, when we know well that medi- 

 cine, as a science, is recognized by its greatest and most illus- 

 trious lights, as at best, only in its nonage; and when we 

 conceive of the vast difficulties and the complexities of the 

 problems that belong to it ! Yet, we have this to console us — 

 that while we may not be able, for want of a thorough knowl- 

 edge of all the facts, and perhaps of a complete and perfect knowl- 

 edge of very many of them, to draw the broadest generalizations, 



