SOILS OF THE ARID AND HUMID REGIONS. 



403 



sions in this volume have been based. The figures for nitrogen and 

 phosphoric acid maybe assumed to be fully comparable ; that of lime will 

 in general represent fully only that which is present in the forms of 

 carbonate, sulfate and humate, and a part of that existing in zeolitic or 

 hydrous silicate form. Of the two potash determinations only the one 

 made in hot extraction will be even remotely comparable, being pro- 

 bably at least 30% lower than would have been obtained by the writer's 

 method. 



Even thus, however, Wohltmann's results are highly in- 

 structive. He gives the following summary of his mode of 

 interpreting such analyses : 



It will be observed that the figures of this table differ ma- 

 terially only in the matter of potash from those given in chap- 

 ter 19, p. 354; for the latter substance they would have to be 

 multiplied by from 2 to 4, according to the lime-content and 

 other conditions. 



With this understanding a number of Wohltmann's analyses 

 of soils from Samoa and Kamerun are given below, the pot- 

 ash determinations made with hot acid being placed in par- 

 entheses after the other. 



Soih of Samoan Islands. A discussion of these analyses shows, from 

 the writer's point of view, a very low content of potash and lime, with 

 the peculiarity that both are somewhat higher at the depth of a meter 

 than in the surface ten-inches. This is probably to be accounted for 

 from the very high content of organic matter (humus), which is apparent 

 from the high " loss by ignition," a very large proportion of which must 

 be credited to the burning of the organic matter. That this humus 

 reaches to the lowest depths examined, is clear from the nitrogen-con- 

 tent given for these samples. Wohltmann, whose estimate of these 

 soils agrees in most respects with the writer's, attributed to them a very 

 satisfactory nitrogen-content. This would be true of the total; but as 



