* 

 154 ACTION OF SOIL ON FOOD OF PLANTS IN MANURE. 



munerative, and science has no power to help him over 

 his difficulties, what is the use of theory ? So says the 

 agriculturist who is himself unacquainted with the 

 essence of theory. 



It is a common error to fancy that an accurate 

 knowledge of theory will give the power of explaining 

 all cases that occur. Theory of itself does not explain 

 a single phenomenon in astronomy, mechanics, physics, 

 or chemistry ; it studies and points out the causes which 

 lie at the foundation of all phenomena, not the special 

 causes upon which an individual phenomenon depends. 



Theory requires that the causes which govern each 

 individual case should be sought out one by one, and 

 then the explanation is the proof or exposition of the 

 manner in which they work together to produce the 

 particular fact. It teaches us what to look for, and how 

 to employ proper experiments in the discovery. 



The reason why we have arrived at no conclusions 

 about the facts just mentioned, depends chiefly upon 

 this, that hitherto the practical farmer has troubled 

 himself very little about the causes of those facts, as, 

 indeed, the investigation of causes is not his proper 

 business ; while those who have undertaken this task 

 show, by the way in which they attempt to discharge 

 it, that they are but little acquainted with the plant as 

 an organised being, having peculiar requirements which 

 must be accurately known by all who would cultivate 

 it properly. 



In the following remarks I shall compare a pea- 

 plant with a cereal, and shall call the attention of agri- 

 culturists to certain peculiarities which have to be con- 

 sidered in the cultivation of both plants. 



A moderately moist, strong soil, not too cohesive 

 and perfectly free from weeds, is particularly suited for 

 peas and barley ; a well-tilled, calcareous loam or marl 

 is the best for both plants. An arable surface soil 6 

 inches deep suffices for barley, which, with its fine- 

 inatted roots spreading in tufts, finds a loose subsoil 

 rather injurious than beneficial. Fresh manuring just 

 before sowing acts powerfully on the growth of barley. 



