314 EXPERIMENT STATION RECORD. 



The detection of pollution in underground waters, and methods of trac- 

 ing the source thereof, J. C. Thresh (Eiu/iii. Xeics, 58 {1901), A'o. 5, pp. 109, 

 110). — This is an abstract of a paper read before the British Association of 

 Waterworks Engineers, which describes the use of sodium chlorid, ammonium 

 chlorid. and fluorescin in tracing the source of pollution in wells. 



The purification of sewage by peat filters, H. Pottevin (Coinpt. Rend, xicad. 

 Set. [Paris] lU {1901), 'No. IJ,, pp. 768-77r^).— Experiments similar to those of 

 Milntz and Lalne (E. S. R., 18, p. 1023) are reported. 



In these experiments two earthenware cylinders 0.85 meter deep were used as 

 the septic tanks from which the sewage was siphoned off every 24 hours upon a 

 filter bed consisting of alternate layers of peat and chalk. Notwithstanding the 

 fact that the experiments were made during the winter at temperatures which 

 were not the most favorable for purification, the organic and ammoniacal nitro- 

 gen was completely oxidized in the case of sewage containing as much as 200 mg. 

 of nitrogen per liter. The whole of the ammoniacal and organic nitrogen was 

 not recovered in form of nitric nitrogen, but apparently a certain variable 

 amount was lost in form of free nitrogen. 



SOILS— FEKTILIZERS. 



The genesis of soils and the principles of a genetic soil classification, P. 

 KossovicH {ZJiin: Opiiitn. Afjroii. [Ritss. Join: E.rpt. Lundii:.], 1 {190G), No. 4, 

 pp. Jfl8-501). — According to the author, the peculiarities and the character of 

 those physico-chemical processes by which the soils were formed must be taken 

 as a foundation for a genetic classification of soils. The soil solution is the 

 medium in which these processes take place and, on the one hand, is determined 

 by these processes and. on the other, influences their character by its composi- 

 tion ; hence it follows that the nature of the soil solution must in the main deter- 

 mine the peculiarities and properties of the soils. The primary difference in the 

 soil solutions which consist mainly of electrolytes is shown in the reaction of 

 the solution which may be alkaline, neutral, or acid. 



Since a neutral reaction can not long be maintained in a soil solution there 

 exist only 2 main types of soil solution — alkaline and acid — and consequently 

 also only 2 groups of soils. The alkaline soil formation which takes place 

 under the influence of alkali salts of weak acids (carbon dioxid and silica) is 

 characterized by the accumulation of bases, mainly sesquioxids, and the leaching 

 out of silicic acid. The acid type of weathering proceeds mainly under the 

 influence of humic acids and is accompanied by an accumulation of silica and 

 the washing out of the bases. In the group of soils formed through alkaline 

 weathering belong those of the deserts and steppes (chernozem), in which 

 strong bases such as soda, potash, lime, and magnesia are present in quantities 

 suflicient to produce an alkaline reaction in the soil solution. The group of 

 soils of the acid type of weathering consists of the gray forest soils and the 

 podzols which do not contain a sufficient amount of lime and magnesia to neu- 

 tralize the humic acids. The eluvial soils may be distributed between these 2 

 types or may represent intermediate or transition forms. — p. fireman. 



Soil solutions: Their role in soil formation, methods of their examination, 

 and their significance for the characterization of soil types, S. A. Zakhaeov 

 {Zhtir. Opuitn. Agron. {Russ. Jour. Expt. Laiidic], 1 {1906), No. J,, pp. 3S8-.ill, 

 figs. 7). — On the basis of a comprehensive survey of the literature and extended 

 experiments with soils of various types, the author arrives at the following 

 general conclusions : The soil extracts and, consequently, the soil solutions of 

 the various soil types differ from one another in color, reaction, total content of 

 soluble substances, and the ratio of the mineral and organic portions. Further- 



