RURAL ENGINEERING. 889 



some system of demerits assigned fioiu diiect mensurements is worthy of 

 further study. 



"The sieve at best is a measure of tlie coarseness of finely ground niateri.il 

 rather than tlie fineness, and experiments now in progress . . . indicate that 

 air separation will offer a more satisfactory means of determining fineness than 

 mechanical sieving," It is further concluded that a tolerance of 1 per cent 

 from the specification should be allowed with the No. 2fK) sieve and 0.5 per cent 

 with the No. 100 sieve, every care being taken to conduct the test in strict 

 accordance with standard methods. 



French tests on oil-mixed concrete, R. Feret (Ann. Fonts et Chauss^es, 

 9. ser., 17 {1913), pt. 1, No. 5, pp. Jil3-Jf36, pi. 1; a'bs. in Engin. Neivs, 70 {1913), 

 No. 25, pp. 1228, 1229). — A series of French tests on the effect of mixing a 

 heavy mineral oil with a concrete on the density and water repelling qualities 

 leads to the conclusion that it is much simi)ler and cheaper to obtain a maxi- 

 mum density of mortar by a judicious choice of sand and by carefully propor- 

 tioning the mix than by the addition of a water-proofing agent. 



Effect of hydrated lime on Portland-cement mortars, H. S. Spackman 

 {Engin. Rcc, 69 {J91Jf), No. 1, pp. 25, 26, figs, i)).— Investigations of the effect 

 on the physical characteristics of the hardened mortar of the addition of 

 hydrated lime to Portland cement to increase the plasticity and impermeability 

 are reported with curves of results. 



It is concluded from these tests that the addition of hydrated lime to cement 

 mortars is to be recommended on the grounds that, in addition to making the 

 mortar more plastic and impermeable, its use will probably result in a re- 

 duction in tendency of the mortars to shrink and crack, greater durability, and 

 probably an increase in strength beyond that needed in the laboratory tests, as 

 the greater plasticity will permit of better work being done by artisans. 



Cement pipes and distributing" stand pipes, B. A. Etcheverry {Jour. Elec- 

 tricity, 31 {1913), No. 10, pp. 216-219, figs. 7).— This article describes and 

 illustrates the underground cement pipe system of water distribution, particu- 

 larly for orchard irrigation. Information is given regarding the location and 

 construction of the system, particularly discussing the construction and opera- 

 tion of the stand pipes containing the regulating valves. 



Some data on reinforcing" concrete pipe, C. E. Sims {Concrete-Cement Age, 

 3 {1913), No. 5, pp. 204, 205).— Tests of the relative value of different methods 

 of reinforcing concrete drain tile showed that single-hoop reinforcement at 

 the wall center and longitudinal reinforcement added little to the strength of 

 the tile. The best results were obtained with double-hoop reinforcement. 



The use of the formula J/=0.075 WD, developed in connection with the tests 

 for computing reinforcement, is illustrated. .1/ equals the negative bending 

 moment at the crown, W is the weight in pounds per inch in length of tile, and 

 D is the diameter of the tile from the wall centers. 



Transverse streng-th of screws in wood, A. Kolberk and M. Birnbaum 

 {Cornell Civ. Engin., 22 {1913), No. 2, pp. 31-41, figs. 4; o^s- in Engin. a)id 

 Contract., 40 {1913), No. 25, pp. 694-696, figs. ^).— The results of tests to 

 determine the strength of ordinary cut screws in single shear in cypress, yellow 

 pine, and oak joints are reported, and the following conclusions are drawn : 



In cypress, the effect of boring holes for the screws is to weaken slightly the 

 joints, while the opposite is true in yellow pine. Friction between adjoining 

 pieces plays only a small part in the strength of the joint. Decreasing the 

 number of screws per joint increases slightly the strength per screw. To se- 

 cure the best results in a wooden joint, the outer piece should be about 0.4 the 

 length of screw. For a particular gage, equal i^enetration into the middle piece 



