RURAL ENGINEERING. 485 



pockets, and that once formed these pockets would quickly develop Into holes. 

 It was also noted that for the hard and tough stones, when used in compara- 

 tively large sizes, the bonding mortar would wear away and allow the rock to 

 protrude, making an uneven and bumpy surface. . . . Where the stone pre- 

 sented lines of cleavage, as is present in many hard stones, the protruding 

 stones would laminate and then kick out. Deep pockets were formed when the 

 laminations ran vertically, the part of the stone between the laminations being 

 dislodged and the remainder of the broken stone, having no backing of material, 

 being dislodged. The softer mortar would then break down, followed by 

 the stones surrounding the pocket, and the small pocket would very speedily 

 develop into a much larger pocket. When the laminations ran horizontally 

 the pockets formed were more or less shallow and the unevenness of the surface 

 was not so pronounced. In the crushed stone specimens this condition of 

 surface was developed at a much later period in the course of rattling than in 

 the case of the gravel rings. 



" In general, the tests show that crushed stone makes a better wearing sur- 

 face than the gravels, this advantage being due to the better bond. It was 

 demonstrated in the case of the sandstone specimens that the stone wore down 

 with approximately the same rapidity as the bonding mortar, producing a 

 smooth, even surface. It is also to be noted that the percentage of wear was 

 normal." 



In the gouging tests " the kicking out of the gravel was more marked. . . . 

 Also the laminated stones were dislodged much more rapidly." 



An investigation of the concrete road-making properties of Minnesota 

 stone and gravel, C. F. Shoop (Univ. Minn. Studies Engin., No. 2 (1915), pp. 

 1+46, pis. V, figs. 6).— This is a detailed report of the above experiments. 



Can we use more fine aggregate? W. K. Hatt {Cement Era, 13 (1915), No. 

 8, pp. 50, 51). — The detailed results of tests previotisly noted (E. S. R., 34, p. 

 87) are reported in this article. 



Suggestions regarding concrete foi' use on the farm, etc., E. D. Wal k e r 

 (Ann. Rpt. Penn. State Col. 1912, pp. 89-98, pis. 6, figs. 2).— General information 

 is given regarding the proportioning and mixing of concrete, building of forms, 

 and placing of the concrete for various farm striictures. 



Compass surveying and the siraplified calculation of farm areas, C. M. 

 THoaiAS (WythevHlle, Ta.: D. A. St. Clair Press, 1915, pp. TT-f92, pis. 4, figs. 

 8). — This book describes the process of compass surveying and the method of 

 computing land areas by latitudes and departures, with illustrative examples. 



Poisoning green timber with sodium arsenite, C. W. Bukrows (Agr. Oas. 

 N. S. Wales, 26 (1915), No. 9, pp. 767-769).— In this note the author calls at- 

 tention to the fact that arsenite of soda has been introduced with marked suc- 

 cess in haistening the killing of ringbarked trees. Trees that ordinarily would 

 take months to kill by the old method are now killed in a few weeks and fre- 

 quently in a few days by the application of arsenic. In order to prevent sucker- 

 ing the operation should be carried on when the tree is dormant Saplings may 

 be cut off low down and th» solution may be dabbad on to kill and prevent 

 snckering. 



Cost of fencing farms in the North Central States, H. N. Hu2XFHret ( U. S. 

 Dept. Agr. Biii. 321 (1916), pp. S2, pfe. 5, figs. 10).— This bulletin contains data 

 obtained by circular letter from 5,837 farmers In Ohio, Michigan, Wisconsin, 

 Illinois, Indiana, Slinnesota, Iowa, Missouri, Kansas, Nebraska, North Dakota, 

 and South Dakota presenting the essential features of farm fence practice in 

 those States. The purpose of the study was to establish economic standards 

 for fencing and fence management. 



