EUEAL ENGINEERING. 381 



no spirals, slight surface undulations, no aquatic vegetation, and in general good 

 construction and favorable conditions. (4) w = 0.015 for concrete-lined canals 

 having conditions similar to those of type 3, but with greater curvature and 

 some debris or other retarding influences. (5) n = 0.016 for concrete-lined 

 canals of average workmanship and medium conditions, having a rough surface, 

 imperfect joints, and sharp curves; also for canals of smooth lining and good 

 workmanship, but having one or more unfavorable conditions, such as sand and 

 gravel in the bottom or projecting joints which decrease the velocity of water. 

 (6) •n.= 0.017 for concrete-lined canals roughly coated, but otherwise in medium 

 condition. (7) h = O.OIS for concrete-lined canals coated as in type 6 and 

 having the bottom more or less covered with, sand and gravel, or else a clean 

 bottom but poor alignment, irregular cross section, broken gradient, or the 

 like." 



Reference is made to experiments with other kinds of lining, and the prin- 

 cipal benefits to be derived from concrete lining are pointed out as conservation 

 of seepage water, increase in cari-jing capacity of the canal, retluction of charge 

 for operation and maintenance, and insurance against damage to crops. 



As regards suitable grades, it is believed that a mean velocity of between 8 

 and 10 ft. per second is about as high as should be adopted in lining canals under 

 ordiuaiy conditions. 



In locating a new canal for concrete lining, it is stated that sharp curves 

 should be avoided if possible, but that the expense of excavation required to 

 lessen curvature should be balanced against the disadvantages and extra cost 

 of lining sharp curves. In discussing the effect of alkali on concrete lining, 

 reference is made to previous studies of this nature (E. S. R., 29, p. 686), and 

 it is stated that good practice in concrete lining construction where alkali must 

 be reckoned with necessitates the following precautions: "(1) Do not use sand, 

 gravel, or water containing alkali; (2) keep soil waters charged with alkali 

 from coming into contact with, the concrete by the use of suitable drainage; 

 (3) give careful attention to the proper proportioning of materials and use 

 more cement than is needed to fill the voids; (4) protect the surface by a thin 

 plaster coat of dense mortar of granular sand; and (5) both the concrete and 

 the mortar used for the lining may be dampproofed by the addition of 5 to 10 

 per cent of semiasphaltic oil when mixing the materials." 



In summing up the results of experiments on the expansion and contraction 

 of concrete, it is stated " that for concrete slab construction such as canal lining, 

 where only one side is exposed and with the other side in contact with earth, 

 a coefficient of expansion of 0.0000045 should be used, but in the case of concrete 

 construction where all sides are subject to equal temperatures and are not 

 under the conditions of moisture and earth contact found in canal lining and 

 similar construction, a coefficient of 0.0000063 can be used with safety." 



The importance of joints in concrete lining for canals is pointed out and 

 various kinds of joints are described and illustrated. A final section gives data 

 in which an effort has been made to show what constitutes current practice 

 throughout the West in the lining of old and new canals. 



Stream-gaging stations and publications relating to water resources 

 1885-1913, Parts I-V, compiled by B. D. Wood {U. S. Geol. Survey, Water- 

 Supply Paper SlfO {.19U), A, pp. 19+XII; B, pp. XIX+21-30; C, pp. XXn+ 

 Sl-42; D, pp. XX+Ii3-62; E, pp. XXI +53-62). —In Part I, a list of publica- 

 tions relating specifically to the North Atlantic coast drainage basins is given, 

 with a similar list of reports that are considered to be of general interest in 

 many sections and which cover a wide range of hydrologic subjects. Brief 

 references to reports published by state and other organizations are also given. 



