1920] RURAL ENGINEERING. 789 



It was found that tho value of the coefhcient of roughness n in the Kuttta- 

 formula, as obtained by experiments in a drain or pipe at any depth of flow 

 less than full, does not necessarily apply to that drain or pipe when flowinj: 

 full. It was also found that the Chezy formula sivcs the same velocity of 

 flow In a pipe flowing one-half full as in one flowing full with the grade constant. 

 The experimental data obtained seemed to disprove this theory, and showed 

 tljjit the exiioneut of the slope ,v is practically 0.5, and that the exponent of 

 the mean hydraulic radius II is two-third.s. From these data a new formula is 

 presented for computing the flow in drain tile, as follows: V=138 RSsi,in 

 which V=the velocity, R=the mean hydraulic radius, and s=the slope. 



A diagram is given showing discharge capacities bf^sed upon this formula 

 covering tile sizes from 4 to 4S in. and grades from 0.04 to 3 per cent. A detailed 

 description of the equipment and methods used is given, together with tabulated 

 data from the experimental work. The data are also graphically reported and 

 the method of developing curves is explained. 



The Tempo drainage ditch, A. E. Vinson and C. N. Catlin (Arizona Sta. 

 Rpt. 1918, p. J.'/6).— Continuing work previously noted (E. S. R., 39, p. 793; 41, 

 p. 379), analyses of the waters discharged from the Tempo drainage ditch for 

 the year 1918 are reported. 



The effect of alkali upon Portland cement, II, K. Steik {Wyoming Sta. 

 Bid. 122 (1919), pp. 38, J'ujs. 23).— This is the second and final report on the 

 subject (E. S. R., 37, p. 788) in which a neat cement and cement and sand luor- 

 •tars varying in strtMigth from 1:1 to 1:5 were subjected to the action of 

 different alkali solutions singly and in different combinations for time periods 

 up to 84 months. 



It was found tliat the chief reacting substance in the cement is lime in the 

 form of calcium hydroxid. Cement put in solutions of alkali salts was found 

 to set as well as in water. Sodium hydroxid and magnesium liydroxid were 

 formed respectively in solutions of sodium sulphate and magnesium sulphate. 

 A solution of magnesium chlorid had the greatest disintegrating efl'ect, due to 

 the action of hydrochloric acid produced by the hydrolysis of this salt. A 

 sodium sulphate solution was more harmful than a magnesium sulphate solu- 

 tion, other conditions being equal. 



The presence of sodium chlorid in solutions of sulphates of sodium and mag- 

 nesium increased their harmful effect on cement. A 5 per cent solution of 

 .sodium sulphate had a stronger effect tlian either the 1 per cent or 10 per cent 

 solutions. The presence of .sodium carbonate in solutions of the other salts 

 retarded the disintegrating effects. Compression strength and tensile strength 

 were not affected in the same degree. Tensile strength decreased more rapidly 

 in all solutions, even when compression strength increased. Solutions of cal- 

 cium sulphate had no bad effects. Water-proofing paints offered protection only 

 for short periods. 



A so-called iron cement resisted the action of sodium carbonate-sulphate- 

 chlorid solution. The other cements tried had somewhat lower tensile strengths. 

 It is concluded that the mixing of cement in weak solutions of sulphuric acid, 

 disodium phosphate, magnesium fluorid, and oxalic acid is of advantage and 

 increases the alkali-resisting qualities. 



Test of timber posts with warp and seasoning cracks, T. W. Greene 

 (Engin. News-Rec, 85 (1920), No. 8, pp. 3f,2, 3/,3, fig. i).— Tests at the U. S. 

 Bureau of Standards of four columns of Virginia pine 4 in. by 8 in. by 8} ft. in 

 length showed that seasoning cracking alone does not appreciably affect the 

 strength of straight columns where the plane of cleavage is parallel to the plane 

 of least dimension. However, any bending or warping produced by seasoning 

 considerably weakens the column. 



