190 EXPERIMENT STATION RECOED. 



" The dragline scraper excavator is . . . especially suited to the construction 

 of ditches and levees of large cross section where the ground is sufficiently stable 

 to support the machine. The scraper excavator is also suitable for ditch cleaning. 



" The various forms of so-called dry-land machines find quite extensive use in 

 drainage. The dipper and orange-peel dredges of the dry-land type are suitable 

 for use where sufficient water can not be had to float a dredge. The templet and 

 the wheel types of excavators are applicable to open land where the soil is 

 neither too hard nor too wet. The ditches cut by these latter machines are 

 superior in hydraulic efficiency to those of similar section cut by any other type 

 of excavator. The dry-land machines should be operated upstream. The hy- 

 draulic dredge is not suited to ordinary drainage ditch construction. It has been 

 used to some extent in cleaning ditches and, with the use of slope boards, has in 

 at least one instance made a satisfactory record in levee construction." 



State highway mileage and expenditures to January 1, 1915 (U. S. Dept. 

 Agr., Office .Sec. Circ. 52 {1915), pp. 6). — This circular, preparetl by the Division 

 of Road Economics of the Office of Public Roads and Rural Engineering, re- 

 ports data showing that in the 20-year period ended January 1, 1915, expendi- 

 tures aggregating $211,859,163 have been made by 39 States for the construction 

 of 35,477 miles of improved roads. 



Other data showing the distribution of expenditures under state control for 

 the year 1914 are also reported. 



Highway bonds, L. I. Hewes and J. W. Glox-er (U. S. Dept. Agr. Bid. 136 

 {1915), pp. 136, pis. 9). — This bulletin presents a compilation of data and an 

 analysis of economic features affecting the construction and maintenance of 

 highways financed by bond issues, and discusses in addition the theory of high- 

 way bond calculations. 



The following topics are covered : County highways, economic value of the 

 market road, cost of highway construction, cost of highway maintenance, the 

 bond issue, total cost of highways, and expediency of issuing highway bonds. 

 The following appendixes are included : State highway bonds ; approximate lists 

 of county and district highway and bridge bonds ; table showing cost elements 

 of gravel, macadam, and bituminous macadam roads in Maine, Massachusetts, 

 and New Jersey ; and theory of interest applied to highway bond calculations. 



Trail construction on the National Forests ( U. S. Dept. Agr., Forest Serv., 

 Trail Construction on National Forests, 1915, pp. 69, pi. 1, figs. 22). — It is the 

 purpose of this handbook (1) to establish a uniform classification of trails on 

 the National Forests in accordance with their use, (2) to establish standard 

 specifications for each class, (3) to describe approved methods of location, con- 

 struction, and maintenance, and (4) to furnish reference data useful in pre- 

 paring estimates and in actual construction work. 



Trails following main valleys and streams are classed mainly as A and those 

 following ridges or tributary streams under B or C. The important points to 

 consider in the location of a trail are enumerated as follows : (DA south ex- 

 posure has less snow, is drier, often more open, and has an increased fire hazard, 

 (2) ridges afford less expensive trail routes than valleys, but the period of use 

 is correspondingly reduced, (3) steep side hills, near the angle of repose, are 

 liable to landslides or snowslides, (4) bridges and temporary structures should 

 be avoided as far as possible, and (5) the permanence of a trail depends on the 

 material and its drainage. Three standard maximum grades for trail construc- 

 tion are given, namely, 6 per cent, 12 per cent, and IS per cent. Twelve per cent 

 is considered the limit for safe mountain roads, while 18 per cent is designated 

 as the maximum efficient trail grade. It is stated that long, steep grades should 

 have breaks at frequent intervals where animals may n-st and recover, which 

 for grades between 15 and 20 per cent should be spaced about 200 to 300 yds., and 



