EURAL ENGINEERING. 191 



Cement and concrete fence posts, II. M. Bainer and H, B. Bonebkight {Colo- 

 rado Sta. Bui. 1^8, pp. 3-36, p'gs. JO). — As a result of the increasing scarcity 

 and cost of wood and the prohibitive cost of iron fence posts, cement and con- 

 crete posts are beginning to be used as substitutes. Though these are some- 

 what expensive at present, they are long-lived,. present a good appearance, and 

 can be made on the farm. 



Part 1 of this bulletin discusses the materials suitable for their construction, 

 gives directions as to propoi'tions for use, the mixing of materials, and the 

 making, reinforcing, curing, and handling of both poured and tamped posts, 

 describes a homemade concrete mixer designed by the station, and several 

 forms of post molds and wii'e fasteners, and gives other useful data. Part 2 

 reports experiments conducted for the purpose of determining the method of 

 building the best posts at the least cost. In these experiments a total of 238 

 line posts and 8 corner posts, variously constructed and reinforced, were tested 

 as to breaking strain under conditions as nearly like those of fencing as possi- 

 ble. The results are reported in tabular form, and the following conclusions 

 are drawn : 



" Poured posts are easier to make than tamped ones. They are somewhat 

 more expensive because one mold will make but one poured post per day, while 

 the same mold may be used for making as many tamped posts as the builder 

 can mix and tamp in the same time. 



" According to the tests made poured posts ai-e a little over 25 per cent 

 stronger than tamped ones of the same size, mixture and I'einforcement. 



" I'oured posts are not so porous as the tamped ones and iire therefore more 

 nearly waterproof, thus making them better able to withstand the action of 

 frost and alkali. 



" The poured post is enough better in every respect to justify its construction 

 and use in preference to the tamped one. 



" Most commercial molds make a post which tapers from the base to the 

 top, but the most economical mold is one which casts a post as large at the 

 ground line as at the base, tapering from the ground line to the top. . . . 



"The best form of post is one which is equally strong from all directions. 

 The square, or round post, fulfills this requirement. The triangular post does 

 not meet the requirements because it can not be economically constructed so as 

 to be equally strong from all directions. 



" To be economical, the amount of reinforcement should be in proportion to 

 the size of the post and strength of the mixture. . . . 



" The material used for reinforcement should be strong, light and rough 

 enough to permit the mixture to get a firm grip upon it. It should be very 

 rigid, with little or no tendency to spring or stretch. 



" The smooth reinforcement tends to slip even if hooked at the ends. 



" Two or more wires twisted together make as satisfactory a reinforcement 

 as can be obtained. 



" Crimped wire tends to straighten and thereby breaks pieces out of the post 

 at the point of greatest stress. 



" The reinforcement should be placed in each corner of the post at a depth 

 of from H to f in. from the surface. . . . 



" The posts should be cured in the shade for at least 60 days, the first 30 

 days of which they should be sprinkled daily." 



Silo construction, L. Carrier (Virginia Sta. Bui. 182, pp. 3-23, figs. 13).— This 

 bulletin describes materials, methods and costs of constructing types of silos 

 which have proved satisfactory and which it is believed will be used in the 

 future. 



