1919] 



RURAL ENGINEERING. 483 



An analysis of the costs of two adjacent ditches in a large swamp, one ex- 

 cavated with dynamite and the other with hand lahor, is given. The yardage of 

 the dynamited ditch was 4,151 and of the hand clw^ ditcli 1,956. The cost per 

 cubic yard of the dynamited ditch was 39 cts. as against 45 cts. per cubic yard 

 for the hand dug ditch. The method of using the dynamite is described. 



Segment blocks have advantages on larger size drains, D. L. Yabnell 

 (Engin. News-Rec, 82 {1919), A'o. 14, pp. 663, 664). — An investigation of the use 

 of segment block for large size drains, made by the Bureau of Public Roads of 

 the U. S. Department of Agriculture is reported from which it is concluded that 

 owing to their cost, lightness, and convenience of handling, and structural ad- 

 vantages over tile their use for large size drains should increase. 



Progressive erosion in a dredged drainage channel, C. E. Ramser {Engin. 

 News-Rec, 82 {1919), No. IS, pp. 816, 877, figs. (J).— Observations on enlargement 

 and effect on capacity due to erosion in the North Fork Deer River drainage 

 channel, made by the Office of Public Roads of the U. S, Department of Agri- 

 culture, are reported. Measurements of six cross sections of a portion of the 

 channel constructed in May, 1915, were made along a course of 700 ft. in April, 



1916, and in January, 1917. A comparison of the plotted cross section showed 

 that after a certain amount of erosion had taken place in the channel erosion 

 did not tend to increase the irregularity of the channel. 



" Between April, 1916, and January, 1917, the average cross-sectional area 

 of the channel increased from 331 to 409 sq. ft. The values of n in Kutter's 

 foi-mula obtained for high stage during the years of 1916 and 1917 were 0.0271 

 and 0.267, respectively, from which it is seen that the roughness coefficient was 

 practically the same before and after the erosion occurred." 



" The mean velocities in the channel were about 4.5 ft. per second, and the 

 discharge capacities for 1916 and 1917 were 1,473 and 1,881 sec.-ft., which 

 represents an increase of 27.7 per cent for the period from April, 1916, to Janu- 

 ary, 1917. The increase in cross-sectional area was 23.5 per cent, which is less 

 than the percentage of increase in capacity." 



It is noted that in the design of this channel no provision was made for a 

 run-off rate to give satisfactory drainage at the beginning, the probable effect 

 of erosion being foreseen and a considerable financial saving being effected 

 thereby. 



Inspection of drainage ditch cross-sections after contract dredging, E. S. 

 Blaine {Engin. Newfi-Rec, 82 {1919), No. 21, pp. 1019-1022, figs. 7).— This arti- 

 cle describes and explains the development of methods for examination of 

 cross sections of drainage ditches after contract dredging. Soundings at first 

 made by level rod gave way to lead and line following along a tape, the boat 

 in use by the sounding man being pulled across the ditch by means of the tape. 



The water supply of Egypt, 1913—14, B. F. E. Keeling {Trans. 3. Internat. 

 coitg. Trap. Agr. 1914, vol. 2, pp. 370-380, figs. 5).— The hydrography of the Nile 

 and methods of water supply for irrigation are discussed and attention drawn 

 to the abnormal dearth of water during 1913-14. Data are submitted to show 

 that under such conditions the rice crop must be sacrificed in favor of the cotton 

 crop. 



Drinking water (Rpt. Min. Agr. Prov. Qnehec, 1917, pp. 100-102). — Sanitary 

 analyses of 13 samples of water from domestic drinking supplies are reported 

 and briefly discussed. Eleven of the samples were found to be contaminated 

 and one v>'as considered doubtful. Details on the bacterial flora of three of 

 the samples are reported, from which it is concluded that " such waters could 

 only disseminate disease and multiply the consumer's liabilities." 



Water purification, J. W. Ellms {New York: McGraiv-Hill Book Co., Inc., 



1917, pp. X+485, /;?s. 6, figs. 168). — It is the purpose of this book to provide the 



