388 EXPERIMENT STATION RECORD. 



Enlarging an irrigation canal, K. A. Hekon {Engin. News, 74 (1915), No. 11, 

 pp. 486, 487, figs. 9). — A concrete-lined irrigation canal was enlarged by rais- 

 ing the lining wall, breaking up one wall with dynamite and moving it back, 

 and lowering the bottom. 



Irrigation weir, measuring rod, and discharge card, K. A. Heron (Engin. 

 News, 74 (1913), No. 6, p. 257, figs. 2). — At frequent intervals In canals of the 

 Modesto project, California, weirs are placeil to allord a vertical drop in grade 

 or to raise the head on a side gate. Movable flashboards are used to obtain 

 the desired head. The structures consist of two or more weirs, each about 3J 

 ft. in length, constructed on a downstream slope of between 35 to 45° from the 

 vertical. Tests of a method of making measurement'^, consisting of holding 

 vertically on the weir crest a J-in. smooth iron rod to determine the head and 

 using this in the Francis formula as though there were no end contractions 

 or slope to the weir, have shown tlie metliod to be sufHciently accurate for 

 practical purposes. 



Life of wood pipe, D. C. Henny (Redam. Rec. [U. S.], 6 (1915), No. 8, pp. 

 354-358; Engin. News, 74 (1915), No. 9, pp. 400-403; abs. in Engin. Rec, 72 

 (1915), No. 6, p. 162). — The author summarizes his experience and reports 

 studies in tabular form on continuous and sectional wood-stave pipe and sec- 

 tional bored-wood pipe, drawing the following conclusions in regard to the 

 relative life of hr and redwood in pipe : 



" Under favorable conditions of complete saturation fir well coated may have 

 the same life as redwood uncoated. Either kind of p\[>e will have a lonc:er 

 life if well buried in tight soil than If exposed to the atmosphere. Such life 

 may be very long. 30 years and over, if a high steady pressure is maintaiui'd. 

 Either kind of pipe will have a longer life if exposed to the atmosphere tluin 

 if buried in open soil, such as sand and gravel and volcanic ash. provide<l in a 

 hot and dry climate it be shaded from the sun. Under questionable conditions, 

 such as light pressure or partially filled pipe, fir, even if well coated, may have 

 only from one-third to one-half the life of re<lwood. Under light pressure the 

 use of bastard staves in fir pii>e should be avoided. 



"The use of wooden .sU^^ves in connection with wire-wound pipe is objection- 

 able and has caused endle.ss trouble and expense. It is possible that the ob- 

 jection may be partially overcome by dipping the ends of sleeves in creo.sote 

 and by applying a heavy coating of tar to the ends of the sleeves. Saturation 

 of sleeve wood will never be as perfect, however, as of the straight pipe, and 

 full creosote treatment of the wood or else some form of metal sleeve, either 

 riveted iron or steel heavily coatetl, or cast Iron, will probably be well worth 

 its extra cost. If wooden sleeves are employed, they should be provided at 

 least for sizes from 10 in. up with individual bands to permit taking up leaks. 



" Pitch seams do not occur in redwood. In fir they should be distinctly 

 liniito<l as to size, frequoncy. and depth. In respect to knots, there appear.s 

 to be no reason for making any distinction betwiH?n the two classes of woo<l. 

 Small, sound knots, If not passing through the full thickness and not occur- 

 ring close to edges or ends might be itorniitted in either wood. Sap is objec- 

 tionable, and the higher cost in prohibiting it entirely or of putting narrow 

 limitations on it is probably justifietl In both fir and redwood, 



" Wooden pipe is not suitable in cases where it can not be kept full and under 

 pressure during periods of use. Coating can not under such condition be 

 expecteil to afford protection against decay. Coating should be continuous 

 and heavy, not less than t^ In. to be fully effective, and should preferably 

 consist of more than one individual coat of a mixture of asphaltum and tar, 

 or of an application of gas tar followed by one or more applications of refined 



