914 • EXPERIMENT STATION RECORD, 



70.r>3 in. and supplied Mitproxiinatcly 17r» ll)s. of clilorin aiul l>.r» Ihs. of nitrogen 

 I)pr iicre." 



The chemistry of the Biver Nile, A. Iatcas (Survey Dcpt., KfJiipt, Paper 

 A^o. 7, pp. 78, (hjm. 1, map. J). — This paper briuRS together what lias alreadj' 

 been publisbod on the water of the Nile eliannels and the matter susi)ended iu 

 it (E. S, K., IS, pp. 421, 424; 10, p. 1013) as well as records of the results of 

 further worlc recently done in the Survey I)ei)artiuent hiboratory of Egypt, and 

 gives a brief outline of work on tlie water iu the soil of the Nile Valley as a 

 basis for future investigations. Appendi.xes give data on the following sub- 

 jects: Bacteriology of the Nile water, preliminary microscopic examination 

 of Nile silts, physical analyses of sauii)les from well borings, chemical analyses 

 of Nile water, and chemical analyses of water from desert wells. A bibli- 

 ography containing 71 references to literature of the subject is given. 



It is stated that " the whole body of underground, water in the valley is 

 simply a lateral continuation of that in the river and is in contact with it and 

 supplied from it." Analyses of these underground waters show wide variations 

 at dift'erent places. "This is only to be expected, since, owing to the varying 

 nature of the soil through which the water percolates, it will naturallj' come into 

 contact with, and will dissolve out, more salts in some places than in others." 



Potable water and sewage (Rev. G6n. HcL, 19 (1908), No. 22, pp. 905-908).— 

 This is a brief review of progress in methods of procuring pure water supplies 

 and in disposing of sewage. Among the methods especially referred to are 

 filtration through submerged, and unsubmerged sand, filters, rapid American 

 filters, and sterilization by means of ozone and iron. The growing use, partic- 

 ularly in England, of the septic tanlc for disposing of sewage is also referred to. 



On the role of bacteria in the biological methods of sewage purification, 

 with special reference to the process of denitrification, W. Mair (.Jour. Uyii. 

 [Cambridge], 8 (1908), No. 5, pp. 609-6.53). — The investigations reported in this 

 paper were carried out in connection with an experimental plant built by the 

 Corporation of Belfast for the purpose of discovering suitable methods of deal- 

 ing with the sewage of that city. The investigations included " an examination 

 of the experimental contact beds, and of the sprinlcler, with reference to the 

 disappearance of certain groups of bacteria," and. a study of " the occurrence 

 of denitrification in sewage with reference to the bacteria concerned in the 

 process, with isolation in pure culture of certain of these bacteria and a study 

 of their chemical effects upon nitrates." 



The investigations on denitrification included more particularly the isolation 

 and study of typical denitrifying bacteria, especially of the Bac'iUuH hypo nit ro.su.<i 

 group, and the relation of the activities of these organisms to the purification 

 of sewage. 



It is thought probable " that in the contact beds a considerable i>roportion of 

 the organic nitrogen disapi>ears as gas as a result of alternate nitrification and 

 denitrification. In the sprinlvler the free exposure to air renders it uulilvely that 

 any appi-eciable amount of denitrification occurs." The general conclusion is 

 reached " that the role of bacteria in the purification of sewage is a somewhat 

 limited one, which by no means justifies the application of such terms as ' bac- 

 teria betls' and 'bacterial purification.' . . . 



" There is, however, one other stage in the process which may with great 

 probability be ascribed to bacterial action, the stage, namely, of nitrification," 

 but thQ author finds it difiicult in view of the results obtained in these investi- 

 gations " to correlate the nitrification which occurs in nature, and in particular 

 that which occurs in sewage purification, with the activity of" the nitrite and 

 nitrate bacteria as isolated and studied by Winogradski. 



