684 EXPERIMENT STATION RECORD. 



or rock, and the whole of the rear mass of (lraina.ue should he carried down to 

 such rock wheu It is within reasouahle depth. 



"When no such niooruni or rock is availiible then the site is not desirable, but 

 if a bank has to be built a large trench should be excavated beneath the rear toe 

 and filled with good drainage material and a berm formed ov(>r it. 



"If a masonry core wall be used in an earthen dam it must be sujiported by 

 earth backing to enable it to resist the thrust of the saturated material on the 

 ui)stream side of the wall. 



" If the cross sections of all sorts of embankments be studied, from that of a 

 small watercourse up to a small tank embankment with 40 ft. depth of water, it 

 will be found that in all cases where the bank is thoroughly satisfactory the 

 hydraulic gradient through the bank is not less than 4 to 1 ; the hydraulic 

 gradient is the slope from the point where the water touches the bank to the 

 rear toe, and is the maxinmm gradient available fur driving (he water through 

 the bank." 



Laud drainage, A. R. Whitson and E. R. Jones {Wiscoiisiti Sla. Bui. 138, 

 pp. .'/O. fit/s. !.')). — The authors include a compilation of data sufficient to enable 

 the design of an open ditch or tile drainage system, and describe in detail several 

 examples of the successful application of drainage in Wisconsin, citing the bene- 

 fits which have accrued in. each case. The practical operations necessary in the 

 construction of tile drains are discussed, and various details of construction are 

 described and illustrated. A brief synopsis of the Wisconsin drainage laws is 

 followed by a discussion of the distrilmtion of benefits, and the luilletin is con- 

 cluded by an appendix on the description and use of instruments used in making 

 drainage surveys. 



The best value of Kutter's " N" to adopt in canal design, [W. G. Ken- 

 nedy] {[Pr(x:~\ Irriy. Coiif., Simla, 190J{, I, p. 175). — In discussing the question 

 the author admits that the values of N worked out from time to time from 

 observed canal discharges vary greatly for the same channel and even for the 

 same site. Sufficient observations have, however, been made to fix N for 

 Indian canals within fairly narrow limits. " On a quite new and well-dressed 

 channel N goes down to 0.020, but with the bed silted and the banks fairly 

 well kept, N is fairly steady at 0.0225 and ought to be adopted as an all-round 

 figure in canal design." 



In the discussions on this subject at the same conference the consensus of 

 opinion seemed to be " that for distributaries or not very large canals, 0.0225 

 is the right value to assume, and for very large canals, 0.020 may safely be 

 taken." One instance was cited where with a discharge of 1.200 to 1,500 cu. ft. 

 per second the coefficient was found to be 0.01(5 to 0.017 ; in another case \yhere 

 the bed width was 250 ft, the depth 9.5 ft., and the discharge S..^,20 cu. ft. per 

 second the coefficient was found to be 0.018. 



Industrial alcohol: Sources and manufacture, II. W. Wiley {V. S. Dept. 

 Agr., Farmers' Bill. 268, pp. 45. p(js. 10). — This bulletin is prepared in response 

 to the general demand for information on the manufacture and use of indus- 

 trial alcohol. The law inider whch this product may be manufactured occupies 

 the first few pages of the bulletin, after which some extracts are given from 

 the rulings of the Conmussioner of Internal Revenue relative to the restric- 

 tions surrounding the production of denatured alcohol. 



The substances used in its manufacture and denaturation are named and 

 discussed. In this connection the suitability of several plants, such as arti- 

 chokes, bananas, barley, cassava, potatoes, rice, speltz, and sweet potatoes for 

 us(> in alcohol production are considered in -some detail, tables being given of 

 the usual starch or fermentable content of (>ach. The comparative value of 

 p(»t;itoes and other root crops for making alcohol is shown by the following 



