RURAL ENGINEERING. 587 



and for different time periods, and each tile after curing was subjected to the 

 pressure test. 



The conclusions from the experiments were as follows : The curing of tile in 

 exhaust or moisture steam for 36 or 48 hours respectively gives the best results, 

 after which no sprinkling or wetting is necessary; 8-in. tile, cured in exhaust 

 steam for 3 days, tested 2,000 lbs. after being 7 days old, showing that two- 

 thirds of the total strength can be developed in 7 days, the highest crushing 

 strength obtained being 3,000 lbs. The curing of tile in air alone is unsatis- 

 factory, although it is materially helped by sprinkling. 



How the engineer may help to prevent troubles from defective drain tile, 

 A. O. Anderson {Engin. and Contract., 31 (1912), No. 25, pp. 705, 706). — ^A pre- 

 vailing neglect among drainage engineers is claimed as to the testing of drain 

 tile and in the making of strict specifications for their strength and the materials 

 of their manufacture. The importance of careful design of tile lines is pointed 

 out, and the general principles of earth pressure in their connection with the 



size and thickness of tile is discussed. The formula for tile design T=.^ - 



IRSF 

 12 M' 



in which !r=the thickness in inches, i2=radius in inches, S=the load in 

 pounds per foot, i^=factor of safety for earth pressure, and M=the modulus 

 of rupture in tile in pounds i>er square inch as determineii by test, is presented. 



A summary is given of the duties of the engineer relative to computing and 

 specifying the depth and width of ditch, allowable loading, modulus of rupture, 

 thickness, absorption, and materials of manufacture for the diflferent sizes of 

 the tile in a drainage system. 



Assessment of benefits in drainage districts, I. W. Hoffmann (Proc. Iowa 

 Engin. Soc, 24 (1912), pp. 78-80). — The author points out certain factors to be 

 considered in making drainage district assessments, such as the kind of land, 

 such as swamp, wet, low, and high, the distance of the different tracts from the 

 proposed drain, the elevation of each tract above its drainage outlet, and actual 

 tile benefits from laterals. 



Supplemental report on Nelson Avenue experimental road, and report of 

 experiments in binding gravel and crushed gravel with tar and asphalt, 

 and also in constructing a waterbound road of gravel, J. C. Wonders (Ohio 

 Highway Dept. Bui. 13, 1910, pp. 19, figs. 17). 



The physical testing of rock for road building, including the methods 

 used and the results obtained, A. T. Goldbeck and F. H. Jackson, Jr. ( TJ. S. 

 Dept. Agr., Office Puh. Roads Bvl. U, pp. 96, figs. 20). — This bulletin, in part 

 a revision of Bulletin 79 of the Bureau of Chemistry, previously noted ( E. S. R., 

 15, p. 826), discusses the agencies destructive of roads and the necessary phy- 

 sical and mechanical qualities of the road materials, describes in detail the 

 physical tests of road material as conducted in the Oflice of Public Roads, which 

 include the hardness, toughness, impact, abrasion, cementation, specific gravity, 

 and absorption tests, and briefly interprets the results of these tests in general 

 on trap, limestone, dolomite, granite, sandstone, chert, gneiss, schist, slate, 

 marble, and quartzite. As an appendix a large amount of data is given of the 

 results of physical tests made on rock samples classified according to their loca- 

 tion and showing availability and character of the materials as far as they 

 have been tested throughout the United States. 



Making better country roads, C. W. Bush (Wis. Country Mag., 5 (1911), 

 No. 11, pp. Ji37-Jf39, figs. 2). — The claim is presented that macadam, telford, and 

 dirt roads are the best country roads, and brief directions for their proper 

 construction and maintenance are given. 



Effect of country roads (Missouri Bd. Agr. Mo. Bid., 10 (1912), No. 5, pp. 

 60, figs. 24). — This bulletin points out the social and commercial advantages of 

 65584°— No. 6—12 7 



