370 



SOILS. 



Unfortunately neither Maercker's method of preparing the 

 soil extract, nor his ratings as given in the table, are accepted 

 by all soil chemists even in Germany. As will be seen by 

 reference to Wohltmann's work on the soils of Samoa and 

 Kamerun (chap. 21, p. 404), his methods and numerical esti- 

 mates differ widely from those given by Maercker, and also 

 from those adopted by the Prussian soil surveys. Reference to 

 the analyses of the soils of Madagascar by Miintz and Rous- 

 seaux, given in the same chapter, page 406, shows still another 

 different method, although as it happens their numerical esti- 

 mates do not differ very widely from those of Wohltmann. In 

 both cases, a special, more incisive extraction is made for the 

 determination of potash. Why the same more energetic action 

 is not used for the other ingredients also, is not stated, and is 

 obscure. Fortunately, in all cases the action is at least suffi- 

 ciently strong to secure the dissolution of all the lime existing 

 in the form of carbonate, and of all, or nearly all, the phos- 

 phoric acid not securely locked up as ferric phosphate; the 

 latter being inert, is of no special interest (see Analyses of 

 Hawaiian Soils, this chapter, page 256). 



