1917] RUKAL ENGINEERING. 585 



" Two years' flooding has been sufficient to reduce the alkali present to an 

 amount which is considered safe for crops. The tests show that although there 

 was originally nearly two and one-half times as much NaCl as Na2C03 in the 

 surface foot of soil this salt is much more easily removed by flooding than the 

 NajCOs, and although the latter has been reduced by 15 per cent there was, at 

 the end of the second year, more than one and one-half times as much NusCOa as 

 NaCl in the surface foot of soil. . . . The tract has been changed, after three 

 years, from that previously described to one producing a crop of ISO tons ot 

 grain hay in 1916." 



Velocity coefficients for a dredged drainage canal, P. V. Hodges {Engm. 

 News, 76 (,1916), No. 22, pp. 1052, 1053, figs. 6).— Tests of the application of 

 different formulas to the flow of water in a drainage canal 25 miles long, exca- 

 vated by a % cu. yd. dipper dredge in peat soil underlain with clay, are reported. 



It was found by current meter measurements at two sections that the coeffi- 

 cient n of Kutter's formula varied from 0.0253 to 0.0259, and the velocity as 

 computetl with these values had a variation of 2.5 per cent within the range of 



this experiment. The coefficient m of Bazin's formula, V= — J RS 



552-|- 7n' 



71 

 varied from 1.127 to 1.1 04, and the velocity as computed with these values had a 



variation of 2 per cent. The coefficient C in the exponential formula y= (7/2" *'.§"'" 



varied 4 per cent. To obtain a formula that applies more closely to the law of 



flow in tills canal, the formula V=K{RS)'"^'^ was derived, in v.hich K=229.6 



The value of the coefficient K varied 1.8 per cent within the range of this 



experiment. 



Tlie value of n was found to decrease as the velocity or hydraulic radius 

 incn-asod, the condition of the channel remaining the same. 



Keduction of seepage losses in a canal through, porous shale, J. H. Mi nek 

 (Reclam. Rec. [t7. S.}, 7 (1916), No. 12, pp. 56S-570, fig. i).— Experiments con- 

 ducted on canals of the Grand Valley Irrigation Project showed the favorable 

 influence of artificial silting of canals in markedly reducing conveyance losses. 



" The protective measures adopted consisted in excavating the canal through 

 shale to a depth of 1 ft. below the required grade, with a view of allowing silt to 

 accumulate in this extra depth. . . . Part of the earth lining was placed before 

 water was turned into the canal and part afterwards. The work done with the 

 water in the canal was the more effective in that the material compacted better 

 and more quickly and also spread farther out on the canal bottom."' 



Care and attention necessary for maintenance of metal flumes, F. D. Pylk 

 {Reclam. Rec. [U. S.], 7 {1916), No. 11, pp. 519, 520; ret: in Engin. Rcc, 7.i 

 {1916), No. 21, p. 622). — Experiments with seven paint and tar mixtui'es. includ- 

 ing African black, Egyptian black, elastic gi-aphite, green gi'aphite, tar com- 

 pound, coal tar, and green paint when used as pre.'^ervatives for metal flumes 

 on the Uncompahgre Project, are reported. 



It was found " that the coal tar, coal-tar compound, and elastic graphite Avere 

 the only mixtures that could stand one season's use, and there was som.e doubt 

 as to the elastic graphite standing another season. It appears from observa- 

 tions on this project and the observations of project managers on other projects 

 that coal tar is the best and cheapest mixture available. In some instances a 

 first coat of water gas tar has been applied before the coal tar with excellent re- 

 sults. In tarring flumes care should be exercised to clean the surface thor- 

 oughly. All joints should be carefully tarred. It may be advisable to hot dip 

 all sheets before they are placed in the flume." 

 85476°— No. 6—17 7 



