THE CHEMICAL PROCESSES OF SOIL FORMATION. 25 



Yukon and Dwina show wider differences than any two other 

 waters in the list, unless it be the St. Lawrence, another 

 northern stream. The Missouri and Rio Grande show by 

 their high content of soda, chlorin and sulfuric acid their 

 origin in arid climates, where alkali lands prevail. The water 

 of the Nile is here represented by two analyses, 1 one showing 

 the season when the water is " red " and of high fertilizing 

 quality because of the sediment it brings down from the 

 mountains of Abyssinia; the other the " green " and relatively 

 clear water which comes from the great lakes and through the 

 " sudd " or grassy swamp region near the junction of the 

 Gazelle river with the Nile. Of the analyses given of the 

 Mississippi river water, the first represents the average of a 

 full year's observations made weekly under the auspices of the 

 New Orleans Commission on Sewerage and Drainage, by J. 

 L. Porter. The fourth is an analysis made of water taken at 

 the same point in May, 1905 ; the analysis having been made in 

 full by Mr. Stone, of the Reclamation Service of the U. S. 

 Geol. Survey, the direct determination of potash and soda 

 being in this case included. As will be seen, and might be ex- 

 pected, the average of the Mississippi water corresponds quite 

 nearly to that of nineteen of the world's great rivers as given 

 by Murray. The very great variation in the content of sul- 

 fates is evidently due to the occasional heavy influx of the 

 gypseous waters of the Washita and Red rivers when in flood ; 

 while the minimum content (in January) agrees almost pre- 

 cisely with the general average. Murray's table would hardly 

 be changed if these analyses of Mississippi water were incor- 

 porated therein, owing doubtless to the large and varied 

 drainage area of the great river. 



Sea Water. The nature of the substances permanently 



1 The correctness of Letheby's analyses has been disputed, partly because of their 

 disagreement with former analyses in the very high amount of lime, partly because 

 of the high potash-content in the Low-Nile water. The lime content is, however, 

 confirmed by the partial analyses made by Matheyin 1887, which gives an average 

 of 44.1 for the year, while the older analyses, made in Europe, of transported water 

 gave only half as much. Letheby working on the spot was doubtless more nearly 

 right in this respect. His figure for potash in the " Low-Nile " water agrees with 

 former determinations, but that in the " High-Nile " is approached only by that in 

 the Dwina water. It may be suspected that the soda is too low and potash too 

 high in this analysis. 



