KURAI> KNlil.XKKKlNG. 

 C'ciiK III idliKs of mi.nd rue/.- ilii-fts. 



485 



III tile opinidii of the w ritor, these results iiuliciite that "the road builder 

 should blend his material. .>-o as to briiij; alKuit the u^reatest aiuoiint of decompo- 

 sition possible anions the road jiartioles on which he; depends for the formation 

 of the bonded surface of liis road." 



The construction of sand-clay and burnt-clay roads, W. I.. Spoon ( I . >S'. 

 .ihpl. I///-.. Office Pill). Roads Bill. 27. pp. J9. p/.v. '/. pi/x. ■'>)■ — 'I'lds bulletin dis- 

 cusses the iiivesti^'ations made by the Oftice of Public Roads on the use of a 

 mixture of sand and clay for the improvement of roads, and upon the utilization 

 of burnt clay for road construction. 



By the use of a proper mixture of sand and clay it has been found possible 

 lo construct roads throuiih localities where the prevailin,i; soil is either sand or 

 clay or an objectionable mixture of both. These roads are well adapted for light 

 tratlic. are less noisy, less dusty, and more resilient than the average macadam 

 road, '{'he best sand-clay- road is one in which the wearing surface is composed 

 of sand, and in wliich the spaces between the particles are eutii'ely filled with 

 ( lay. Such a mixture is best secured by thoroughly mixing the right proportion 

 of the two ingredients with water. In practice the clay is first spread on the 

 road and the larger lumps broken tip. The surface is spread with a few inches 

 of sand immediately after a hard rain, and the mixture then thorotighly stirred 

 by a turning plow or disk harrow. The cost of sand-clay roads varies with local 

 i-onditions. but may be taken at if300 to $800 per mile, the character of the 

 fnundation, whether sand or clay, making no difference in the cost. 



In the improvement of roads through "gumbo" soils of the Yazoo district 

 of Mississippi, simple burning of the clay upon the road surface was resorted to. 

 ^Y(lo(l. i>rocured adjacent to the I'oad, is used as fuel, 1 cord being required per 

 s liiii'ai- ft. of a 12-ft. road. After deeply plowiug the road transverse furrows 

 are formed, across which the wood is laid. Lumps of clay and more wood are 

 liiled on this. A third layer of wood parallel to the first is then put on and 

 finally covered with a layer of finer clay to a depth of not less than (i or 8 in. 

 Fifteen to twenty flues are fired at once, and the process of combustion made as 

 uniform as possible. After the burning pi'ocess is complete, the material, which 

 is entirely changed in character, having no tendency to form mud when wet, is 

 rolled down and tniii]p;Htcil. forming a road .surface Ct to S in. in thickness. 



The total cost jtcr mile of such construction, as based on the experiments ear- 

 ned (III. is .$1,478. It is thought that any soil which bricks or clinkers at com- 

 paratively low temperatur<> is suitable for the work. Koads constructed by 

 this method are said lo ln' successftil so far and to sustain ti-aflic in cvcmi the 

 wettest weather. 



Waterproof roads as a solution of the dust problem, 1). Mackenzie (Eii(/i- 

 nrcr [Loiuhm]. Jd.! {lilii(i). A o. .t(l',.i. mi. 1S~). l,Si;). — A jtaper read before the 

 British Asociation. York, 1J»0<>, in which the author discusses the question of 

 obviating the dust nuisance. 



After conmienting upon the failure of tin' oil (ir tar Irc.ilnieiit because of its 

 short jieriod nf usefulness and ol)Jecti(inaiile features fi-oni llie standiiciiil of 



