186 EXPERIMENT STATION EECORD. 



Au experiment begun at Birniingbam, Ala., consisted of building a 24-ft. tar 

 macadam road, witb 5-ft. sboulders, out of an old road. Tar, tar slag, and tar 

 slag limestone ^A•ere used, the tar being a coke oven by-product of specific 

 gravity 1.1G9. The average total cost per square yard was $1.10. 



Three experiments were begun in Kansas to determine if sand clay could be 

 used as a wearing surface capable of resisting the action of the constant winds, 

 and in one experiment clay was used to form a hard top surface on a bridge 

 approach. The cost per square yard of this clay treatment was from 10 to 

 14 cts. 



Of the earlier experiments reported upon, the sections of road at Wayland, 

 Mass., were inspected about 13 months after treatment. The special tar 

 preparation employed on 2 of these sections proved to have given greatest satis- 

 faction, and the other tar experiments showed varying results. It is reported 

 that these experiments seem to indicate that a properly refined coal tar is much 

 preferable to a crude tar. 



At Bowling Green, Ky., where rock asphalt was used as a binder and also to 

 fill the voids of a fresh macadam surface, the road was found to be smooth and 

 free from ruts. Crude oil had been satisfactory as a dust layer. 



At Jackson, Tenn., the tar treatment was found to be on the whole satisfac- 

 tory, confirming results previously reported. Oil, where used on a country 

 road, proved beneficial in preventing raveling and washing and in laying dust. 



Illinois experimental macadam roads {Good Roads Mag., n. ser., 10 {1909), 

 No. 5, PI). 158-161. flij-s. (i). — This is an abridgment of a report as to the con- 

 dition of several experimental macadam roads constructed in Illinois under the 

 direction of the State Highway Engineer. 



Among the findings it is reported that the sticky and gumbo soils apparently 

 furnish the most solid foimdation, while the most treacherous conditions exist 

 on hilly roads where seepy places occur and where there is often encountered 

 more open or porous soil. 



The chief deterioration of the roads was found to be caused by mud tracked 

 upon them, and the report includes suggestions as to methods of protecting the 

 ends of roads to prevent this. 



Tables of construction cost of some of the roads are given, with brief de- 

 scriptions. In this connection it is stated that there is a prevailing impression 

 that the average cost per mile is not over $2,000 or $3,000, but that it is im- 

 possible to construct good roads at such figures. 



Agricultural machinery and implements, E. Weobel (Landwirtschaftliche 

 Maschhien iind Geratc. Hanover, 1907, pp. 218, figs. 1^0). — The object of this 

 book is stated to be to explain the construction and use of machinery with refer- 

 ence to the peculiar purpose of each machine and its parts. An introductory 

 chapter deals with soils and soil cultivation, and the essential mechanical and 

 physical processes of plant growth. There is a brief review of the present status 

 of the agricultural machine industry in Germany, followed by a detailed de- 

 scription of plows, cultivators, harrows, manure handlers and spreaders, drills, 

 weeders, and other implements for the cai-e of plants. 



Agricultural machines, K. AValther (Die Landwirtschaftlichen Maschinen. 

 Leipsic, 1908, pp. 132, figs. 91). — This is the first of a series of books on the 

 subject of agricultural machinery, and treats of machinery for cultivating soils 

 and plants. The construction and mode of operation of various types of plows, 

 cultivators, harrows, fertilizer distributers, drills, and machines for the care of 

 plants are explained in detail. There is also included a chapter on the con- 

 struction and management of machinery used for mechanical cultivation. 



[Traction plowing] (Canad. Thresherman and Farmer, 12 {1909), Xo. .'/). — 

 This number is especially devoted to traction plowing, and contains a brief ac- 



