KURAL ENGINEERING. 



885 



virus of epitholioma contagiosum does not prevent the contraction of roup. 

 Under the conditions of our experiment, epithelioma contagiosum was not 

 fatal to mature fowls, while all that contracted roup died. The cell inclusions 

 present in the hyperplastic epithelial cells of epithelioma contagiosum show 

 changes which may perhaps represent stages in the development of a protozoan 

 parasite, but we are unable so to connect them that a complete life cycle is 

 definitely established." 



A bibliography of 20 titles is appended. 



RURAL ENGINEERING. 



Frictional resistance in artificial waterways, V. M. Conk, K. E. Trimble, 

 and P. S. Jones (Colorado Stn. Bui. 104 {lOlJf), pp. Jf8, figs. Jfl).—A series of 

 field experiments in cooperation with this Office with metallic, reinforced con- 

 crete, and timber flumes, concrete lined and earth canals, concrete and timber 

 chutes, and inverted siphons of wood-stave pipe are reported which were con- 

 ducted to determine (1) the coeflicient of roughness in empirical formulas for 

 the several types of open channels; (2) whether such coefficient changes with 

 variations of discharge; and (3) the loss of head in water flowing through 

 siphons, to compare Kutter's formula with the ordinnry fricti«»n formula as 

 adapted to pressure pipes, and to compare the accuracy of difl'eront methwls of 

 making current meter measurements. 



The average values found for the coefficient of friction n in Kutter's formula 

 for the several types of open channel were as follows: (] ) Semicircular metallic 

 flumes, smooth water face, wasteways less than 100 ft. long, 0.021; smooth 

 water face, 0.011 ; joint connections protruding into the waterway, 0.0174 ; corru- 

 gations at right angles to the line of flow, 0.0225. (2) Timber flumes, lined with 

 patent roofing materinl, 0.016; planed lumber, battens on the sides, flooring 

 placed transversely, 0.015; planed lumber, battens on the sides, flooring placed 

 longitudinally. 0.012; planed lumber, no battens, perfect alignment, 0.011. (.3) 

 Concrete-lined channels, smooth concrete or mortnr-finislied surface. 0.012; sur- 

 face unplastered as left by forms, 0.016 ; bed exceptionally smooth, fine silt, uni- 

 form cross-section, straight alignment, 0.017; bed of hard, water-worn adobe, 

 0.022; bed of coarse gravel and small loose stones, 0.024; banks, smooth clay; 

 bottom, fine sand ; grass hanging into water, 0.027 ; bed, hard, water-worn adobe, 

 many fine roots projecting, 0.028; bed, fine silt, merging into clay, many large, 

 loose stones, 0.030; bed. little gravel, mainly smooth, rounded stones, 0.032. 



The following table gives the hydraulic elements as found for wood-stave 

 siphons : 



Hydraulic elements of icood-stare siphons. 



' Value of (c) in Chezy formula V^CtJrs. 

 2 Value of (n) in Kutter's formula. 



• Value of if) in formula for lost head due to friction and curvature, h=f 



L 22 

 d 2g 



