RURAL ENGINEERING. 387 



unscientific design, lack of rolling, incorrect proportions, improper materials 

 or their defective preparation, mixing or careless placing, improper finish of 

 wearing surface, faulty joints, neglect of protection, inadequate curing, and 

 inspection. 



Tests of concrete and brick pavements {Bnyin. lice, 68 (1913), Xo. 17, pp. 

 457, 4o8, figs. 4). — Tests were made on concrete and brick pavements by means 

 of a so-called '* determinator " designed by the department of public works of 

 Detroit. A test space 40 ft. square was divided as follows: In half of the space 

 a l:li:3 gravel concrete pavement was laid, in one-fourth of the remaining 

 space crushed granite concrete, and in the remaining space a brick pavement 

 composed of two sections similar in all respects except that one had a 1 : 5 

 mortar cushion and the other an ordinary sand cushion. 



The determinator consists essentially of a central vertical column or pivot 

 around which revolves a horizontal shafting having heavy cast-iron wheels on 

 each end 48 in. in diameter with rims 3 in. wide. The weight transmitted to 

 the floor by each wheel is 1,650 lbs. To reproduce the wear due to rough shod 

 horses each wheel is provided with 5 plungers on the ends of which are metal 

 plates having 4 steel calks. As the wheels revolve, these plates strike the sur- 

 face of the pavement a heavy blow, estimated in this test at loO lbs. 



After 19,315 revolutions of the machine the gravel concrete had worn badly 

 and unevenly, as much as IJ in. in places, while the granite concrete showed 

 only little wear and that very even. The brick section laid on a mortar 

 cu-shion was in excellent condition while that on the sand cushion was begin- 

 ning to disintegrate. 



The use of mechanical power in German agricultural work, II. K. Schwan- 

 ECKE (FiihUng's Landw. Ztg., 62 {1913), Nos. 2, pf- 41-65; 3, pp. 95-lOb, figs. 3; 

 7, pp. 242-272; 8, pp. 2S6-306; 12, pp. ^2M43).— This article deals at length 

 with the comparative efliciencies and economies of the various forms of power 

 used in German agricultural work. The investigations are grouped under 3 

 heads: (1) Small power up to 15 h. p. for belt work confined to the farm j-ard. 

 (2) power for heavier field machinery and for transportation, and (3) electric 

 power plants and central power plants. 



For work confined to the farm yard and requiring up to 15 h. p. it is con- 

 cluded that wind power, when available, may be profitably used in spite of the 

 high initial cost of the plant. In case wind power is not available and where 

 an all-purpose power from 8 to 15 h. p. is desired, the small portable steam 

 engine is concluded to be the most practical and economical if the engine oper- 

 ator can be profitably employed at other work when the engine is not in use. 

 For smaller belt work the internal combustion engine may be profitably em- 

 ployed and also the electric motor, providing the price for electric current does 

 not exceed 15 pfennigs (3^ cts) per horsei)ower hour. Steam power is concluded 

 to be in general the most efficient and economical power for the heavy field work 

 of plowing, threshing, etc., where several related operations are combined into 

 one operation. 



A .comparison of motor trucks and horses for transportation purposes indi- 

 cates that the former may be used with economy only in case special apparatus 

 for loading and unloading is used and where the truck is used at least 70 or 

 SO days a year, carrying a full load on an average of not less than 30 km. 

 (18.6 miles) daily. The use of motor trucks is concluded to be uneconomical 

 for farms smaller than 375 to 500 acres. 



The article further considers small private electric power plants and central 

 power plants, giving information regarding the installation and oi>eration of the 

 former and data on the cost of power from both. 



32052°— Xo. 4—14 7 



