478 EXPERIMENT STATION RECORD. [Vol.43 



tern of combined drainage and irrigation of swamp land in Argentina is de- 

 scribed and experience in tbe design and development of the different engi- 

 neering features discussed in some detail, with drawings of different struc- 

 tures. Drainage is accomplished both by tile and open drains, and the drain- 

 age water is partially utilized for irrigation by pumping from oi)en drainage 

 canals and storage reservoirs. 



The flow of water in dredged drainage ditches, C. E. Ramser (U. S. Dept. 

 Agr. Bui. 832 (1920), pp. 60, jils. 20, figs. i3).— This bulletin reports and sum- 

 marizes a series of experiments to determine the values of the roughness 

 coefficient n in Kutter's formula which will proi^erly apply to the various con- 

 ditions of dredged drainage channels. The experiments were conducted in 

 Lee and Bolivar Counties, Miss., western Tennessee, western Iowa, southern 

 North Carolina, and eastern Florida. 



It was found that a deposit of sliclv, slimy .silt on the sides and bottom of 

 a channel and the clearing out of perennial growth reduce frictional resistance 

 to flow and increase the capacity. The growth of grass and weeds and the 

 accumulation of drift trees, logs, and other obstructions in the channel greatly 

 decrease the capacity. After a certain amount of erosion has taken place in 

 a channel, further erosion does not necessarily increase the roughness of the 

 perimeter. 



The roughness coefficient n was found to be appreciably higher for a roughly 

 dredged channel than for a smoothly dredgetl one, and abrupt vai-iations in 

 cross section are active in reducing the hydraulic efficiency of a channel. 

 Ordinarily a dredged channel quickly deteriorates in hydraulic efficiency unless 

 systematically maintained. 



The conclusion is drawn that generally in designing a proposed dredged 

 channel a value of n of 0.03 should be used if the channel is to be smoothly 

 dredged and of 0.035 if roughly dredged. If these values are used, the channels 

 should be carefully maintained, and if not to be so maintained a value of n 

 should be selected in accordance with the worst anticipated conditions for the 

 channel. In computing the capacity of an existing channel the value of n 

 chosen should, whenever possible, be based upon a comparison of the condi- 

 tions in the existing channel with the conditions of channels for which values 

 of n have been determined. 



Community tile drainage construction, J. R. Haswell (U. S. Dept. Agr. 

 Yearbook 1919, pp. 79-93, figs. iO).— Several small community tile drainage 

 organizations are briefly described, and data are given on operation, especially 

 with ditching machinery. 



Information on the divining rod, Maeage (Rev. Sci. [Paris], 58 (1920), No. 

 3, pp. 72-80, figs. //). — A number of experiments on the use of the divining rod 

 for locating underground water supplies are described, the author apparently 

 being a believer in this method of discovering underground water. 



Importance of hygienic inspection of Avells in securing a supply of pure 

 potable water, L. Kroeber (Schweis. Apoth. Ztg., 55 (1917), Nos. 19, pp. 27 Jf- 

 277; 20, pp. 287-290). — On the basis of his studies the" author expresses the 

 opinion that chemical examination alone is not sufficient, but that the analyst 

 must secure the sample personally and examine the surrounding conditions, with 

 particular reference to closets and agcumulations of kitchen wastes. 



Methods of chemical examination for chlorin contamination are briefly 

 outlined. 



The purification of moorland water supplies, E. G. Blake (Sci. Prog. 

 [London], U (1920), No. 56, pp. 659-664)-— Information is given on the in- 

 Btallation of moorland water supply systems for rural use in England, with 



