THE PHYSICO-CHEMICAL INVESTIGATION OF SOILS. 315 



recognize the causes of the observed vegetative preferences', 

 we should be enabled to project that recognition into those 

 cases where native vegetation is not present to serve as a 

 guide; and we might thus render the physical and chemical 

 examination of soils as useful practically, everywhere, as is, 

 locally, the observation of the native growths. To a certain 

 extent, such knowledge would be useful in determining the 

 salient characters of cultivated soils, also ; and would be the 

 more useful and definite in its practical indications the more 

 nearly the cultural history of the land is known, and the less 

 the latter has been changed by fertilization. For, so soon as 

 the first flush of production has passed, the question of how 

 to fertilize most effectually and cheaply demands solution. 



It was from this standpoint, suggested by his early experi- 

 ence in the Middle West and subsequently most impressively 

 presented to him in the prosecution of the geological and agri- 

 cultural survey of Mississippi, that the writer originally un- 

 dertook, in icS57, the detailed study of the physical characters 

 and chemical composition of soils. It seemed to him incred- 

 ible that the well-defined and practically so important distinc- 

 tions based on natural vegetation, everywhere recognized and 

 continually acted upon by farmers and settlers, should not be 

 traceable to definite physical and chemical differences in the 

 respective lands, by competent, comprehensively-trained scien- 

 tific observers, whose field of vision should be broad enough 

 to embrace concurrently the several points of view geological, 

 physical, chemical and botanical that must be conjointly con- 

 sidered in forming one's judgment of land. Such trained ob- 

 servers should not merely do as well as the "untutored 

 farmer," but a great deal better. 



"Ecological" studies. Yet thus far we vainly seek in gen- 

 eral agricultural literature for any systematic or consistent 

 studies of these relations. \Ye do find "ecological" lists of 

 trees and other plants, or " plant associations," growing in cer- 

 tain regions or land areas, described in some of the general 

 terms which may refer equally well to lands of profuse pro- 

 ductiveness, or to such as will hardly pay for taxes when cul- 

 tivated. Or when the productive value is mentioned, the 

 probable cause of such value is barely alluded to. even con- 

 jecturally, unless it be in describing the " plant formations " 



