788 EXPERIMENT STATION EECOED. 



Engineering of tliis Department for measuring the wear of concrete roads is 

 described in detail and illustrated. It " essentially consists of a fine wire 

 stretched tightly across the road at a constant height, together with an inside 

 micrometer for measuring the distance from the road surface to the wire. 

 Measurements taken 1 ft. apart across the road permit the plotting of its cross 

 section, and if these measurements are repeated at long intervals the change of 

 cross section or the decrease in the thickness of the road will be revealed." 



Public highways: Kansas roads, past, present, and future, AY, S. Gear- 

 HAiiT (Bien. Rpt. Kans. Bd. Ayr., 19 (1913-14), pp. 56-120. figs. 5S).— This 

 article points out the benefits of good roads to Kansas farmers, and discusses 

 Yi some detail the location, design, construction, maintenance, and financing 

 of the different types of roads in Kansas. 



Economic factors all important in i-ural highways, L. "W. Page (Engin. 

 Ilcc, 112 (1915), No. 13, p. 3S5, fig. 1). — The principal factors which affect the 

 economic efficiency of an improved road, and upon which it is thought economic 

 comparisons should be based, are discussed as cost of construction and main- 

 tenance, amount and character of traffic, and the average unit cost of hauling 

 before and after the improvement is made. With special reference to the 

 kst factor, it is stated that " if the improvement is to be justified economically 

 I the] total annual saving must be sufficient, after all costs for maintenance 

 and repairs are deducted, to pay a reasonable interest on the original invest- 

 ment. . . . The State is much better circumstanced for planning and supervis- 

 ing road improvement work than are any of its political subdivisions." 



A diart is shown wliich is intontled to illustrate the scope of a model state 

 organization. See also a note of a previous report along similar lines by 

 Tennypacker (E. S. II.. 33, p. 290). 



Effects of varying mixture and ignition timing, V. R. Gage (Poucr. .i2 

 (1915), No. 21, pp. 120-122, figs. 2). — Indicatdr diagrams obtained from a 

 6-horseix)wer, 4-stroke cycle, hit-and-miss governed internal combustion engine, 

 operating on different fuel mixtures and with the spark retarded or advanced, 

 are given. These show that " not only maximum economy but also maximum 

 power are obtained by ail justing the engine to run on as lean a mixture as 

 possible, with the spark advanced only enough to overcome the lapse of time 

 required for the mixture to liurn and to overcome the electrical lag." 



The Highland Society's exhibition trial of motor tillage implements at 

 Stirling (Iiiipl. and Mach. Ucv., J,l (1915), No. J,SS, pp. 926, .027).— Trials of 

 four tractor plowing outfits and one motor plow on uniform stiff clay soil and 

 light .soil, with grades varying from 1 in 7 to 1 in 30. are reported, in which it 

 was attempted to simulate actual working conditions on the farm. It was re- 

 quired, however, that " the depth of furrow shall be not less than 8 jn. and not 

 more than 10 in. on the light land and not less than 6 in. on the stiff land." 



It was found that " none of the tractors was successful in ascending the 

 gradient on the plats originally assigned to them on the light land and had to 

 be removed to a part of the field where the gradient was less severe. The 

 presence of a liberal dressing of fresh manure on the surface addetl to the 

 difficulty." It was concluded that the tractors are unable to do field work on 

 a grade exceeding 1 in 20. Under the favorable weather conditions prevailing 

 (hiring the trials no appreciable packing by the wheels of the tractors was 

 observed. 



Test of a potato planter and coverer, A. Nachtweh and K. Vormfelde (Mitt. 

 Verb. Landtr. Mnach. rhifungsanM., 9 (1915), No. 1, pp. 1-9, figs. 5). — A two- 

 row potato planter is described and diagramraatically illustrated, and tests are 

 feoorted. The moiM feature of the planter is a traveling cup chain which lifts 



