786 EXPERIMENT STATION RECORD. [Vol. 40 



practical irrigators and water company officers. Descriptions of, and discharge 

 tables for, rectangular, trapezoidal, and triangular weirs, rectangular weirs 

 without end contractions, and submerged orifices are given. 



Irrigation under the provisions of the Carey Act, G. Ervin {U. S. Dept. 

 Afir., Off. Sec. Circ. 124 {1919), pp. 14)- — This circular gives statistical data 

 showing the number, size, and location of irrigation projects operating under 

 the Carey Act. 



" The following States have accepted the terms of the Carey Act in the order 

 of the date of acceptance: Wyoming, Montana. Idaho, Colorado, Oregon, Nevada. 

 Washington, Utah, Arizona, and New Mexico. In only the first five of these 

 has any actual reclamation taken place under the act." About three-fourths of 

 the total area reclaimed is located in Idaho. 



Failures of irrigation projects under the Carey Act are attributed to the fol- 

 lowing causes: (1) Lack of thoroughness in making preliminary surveys, (2) 

 underestimation of cost, (3) lack of proper State and Federal supervision, (4) 

 slow rate of settlement. (5) allowing settlers to make their homes on the land 

 before completion of the project, (6) ignorance on the part of setters of diffi- 

 culties to be overcome, and (7) requirement that water rights be' paid for in 

 10 years or less. 



Freezing and thawing effect on concrete, A. B. McPanif.t. {Concrete [De- 

 troit. Mich.], 13 {1918), \o. 3, p. 84).— Tests at the Illinois Engineering Experi- 

 ment Station of 345 specimens of concrete made in 0-in. by 12-in. cylinders of 

 1:1:2, 1:2:4. and 1:4:8 mixtures Led to the conclusions that "in general, 

 for any of the three mixtures, and under a uniform temperature of aboul 70" 

 F., there was an increase of strength with age within the limits of the ; 

 Fortius normal temperature, the rate of increase in strength decreases with the 

 age of the specimen. The rate of Increase varies with the richness of the mixture. 

 For the specimens tested, under normal hardening conditions of from GO to 70°, 

 the compressive strength of the concrete subjected to a uniform temperature 

 at the ages of 7, 14, and 21 days may be taken as approximately 80, 80, and 

 05 per cent for the 1:1:2 mixtures, as 50, "."., and 90 per cent for the 1:2:4 

 mixture, and as 40, G5, and S5 per cent for the 1:4:8 mixture, of the strength 

 at 2S days, respectively. 



"The loss in strength due to the alternate freezing and thawing conditions 

 (1) decreases with the Increase in the lenu'th of the Initial setting period at a 

 normal temperature. (2i increases with the Dumber of reversals, and (3) de- 

 creases with the richness of the mixture. In Croup 2, in which the specimens 

 received an initial storage of 4, S. 12, and 24 hours, the loss of strength is 

 much greater than that of Group 1, in which the initial storage periods were 

 2, 6, 10, and 14 days. In Group 2 thos,> specimens having had two reversals, 

 show greater loss of strength than those having had only one reversal for the 

 same initial storage periods. Under similar conditions, the richer mixture shows 

 less loss in strength. 



"When concrete of a 1:1:2 mixture is stored at a normal temperature of 

 about 70° for initial storage periods of 4, S, 12, and 24 hours, the percentage 

 loss of strength after one reversal of one day at 20° and one day at 70° may 

 be taken as about 50, 40, 25, and 10 per cent after one reversal, and 70. 65, 50. 

 and 35 per cent after two reversals. The percentage values are based on the 

 strength of the concrete for the same ages stored at a normal temperature of 

 about 70°." 



How lime affects strength of cement mortar. M. O. Fitter {Concrete [De- 

 troit, Mich.], IS {1918), No. S, p. 83, figs. S).—A series of tests on Portland 

 cement mortars are reported, in which it was found that " from 5 to 12.5 



