ON THE CULTIVATION OF THE EARTH. 



" mining the cause of its sterility, which must 

 " necessarily depend upon some def ect in the 

 " constitution of the soil, which may be easily 

 " discovered by chemical analysis ; some lands 

 ". of good apparent texture are yet sterile in a 

 " high degree, and common observation and 

 " common practice afford no means of ascer- 

 " taining the cause or removing the effect. 



" The application of chemical tests in such 

 " cases is obvious, for the soil must contain some 

 " noxious principle, which may be easily dis- 

 * covered, and, probably, easily destroyed. Are 

 " any of the salts of iron present ? They may be 

 " decomposed by lime. Is there any excess of 

 " siliceous sand ? The system of improvement 

 " must depend on the application of clay a.nd 

 "calcareous matter. Is there a defect of cal ' 

 " careous matter ? The remedy is obvious. Is 

 " an excess of vegetable matter indicated ? It 

 " may be removed by liming, paring, and burn- 

 " ing. Is there a deficiency of vegetable matter ?. 

 " It is to be supplied by manure." 



He also says, " The phenomena of vegetation 

 " must be considered as an important branch of 

 " the science of organized nature ; but though 

 "exalted above inorganic matter, vegetables 

 " are yet, in a great measure, dependant for 

 " their existence upon its laws. They receive 

 "their nourishment from the external elements; 



