RURAL ENGINEERING. 281 



Anatomical and Mstolog'ical studies on some new species of avian cestodes, 

 H^LENE BaczySska {Bul. Soc. Netichatel. Sci. Nat., JfO (1914), pp. 187-239, figs. 

 73). — P"'ifteen new species are here dealt with of which two, namely, Davainea 

 penetrans and D. cohni, were taken from the domestic fowl {Gallus domesticus) 

 in West Africa. 



RURAL ENGINEERING. 



Experiments in the use of current meters in irrigation canals, S. T. Habd- 

 ING (U. S. Dept. Agr., Jour. Agr. Research, 5 (1915), No. 6, pp. 217-232). — In 

 connection with experimental work by Scobey previously n(>ted (E. S. R., 33, 

 p. 183) comparisons of various methods of current-meter gaging of irrigation 

 canals were made with measurements in which the velocities at from 70 to 120 

 points were taken. Canals of various types of cross section having discharges 

 varying from 2 to 2,600 second-feet and velocities of from 0.5 to 8 ft. per second 

 were included. 



" In 96 measurements the 0.2 and 0.8 depth, or two-point method gave results 

 averaging 0.73 per cent too high, and the 0.6 depth, or single-point method gave 

 results 4.8 per cent too high. The average variation for a single measurement 

 was 1.5 per cent for the two-point method. If the results for the single-point 

 method are corrected by — 5 per cent, the average variation of a single observa- 

 tion is 2.5 per cent. 



" In 55 measurements the vertical integration method gave results averaging 

 0.76 per cent too high, and an average variation for a single observation of 2.07 

 per cent. The use of three-point methods gave errors greater than the two- 

 point method alone. 



" There were no marked variations of the accuracy of any of these three 

 methods due to difference in velocity, depth, or value of n in Kutter's formula. 



" In 92 measurements to determine the coefficient to be used to reduce the 

 liiaximum surface velocity as measured by small floats to the mean for the 

 entire cross section the coefficient was found to vary with the value of n in 

 Kutter's formula and the size of the canal. For water cross sections of over 

 about 35 sq. ft. the coefficient remains constant for any given value of w. . . . 

 The coefficient varies from 0.6 to 0.91 for different conditions. The average 

 variation of the coefficient for a single observation from the mean values was 

 about 6 per cent, and in one-fifth of the observations exceeded 10 per cent. 



" In 89 experiments on the use of observations of varying numbers of ver- 

 ticals across the width of canals, it appears that in uniform cross sections, 

 such as flumes or lined canals, observations in 8 verticals gave an average 

 within 1 per cent and in 4 verticals within 3 per cent of the discharge obtained 

 within 16 verticals. In earth canals observations in 8 verticals give an average 

 within 3 per cent and 4 verticals within about 9 per cent. For equivalent 

 accuracy about twice as many verticals should be observed in ordinary earth 

 sections as in uniform lined sections. 



" It was found that the use of only 2 verticals located from one-fifth to 

 one-sixth of the width of the water surface from the sides of the section in 

 canals with vertical sides such as flumes, gave results within an average of 

 2.5 per cent. In concrete-lined sections with sloping sides similar results were 

 obtained where the velocities were measured at from one-fifth to one-fourth 

 of the width from the sides, and the areas were secured from the known cross 

 sections. 



" In earth canals 2 points from one-fifth to one-fourth of the width of the 

 water surface from the sides give velocities varying from the mean of the 

 whole cross section by about 6 per cent. Where the depths at these two points 



