1920] RURAL ENGINEERING. 285 



tonnage of traffic on Iowa highways was found to be considerably larger than 

 has been generally supposed, which emphasizes the wisdom of constructing road 

 surfaces of great durability. It is noted that a system of earth roads has been 

 carrying a traffic that would be considered moderately heavy for a paved road. 



ras.senger automobiles overwhelmingly predomhiate in the present traffic. 

 The preset t highways, because of the extreme variations in the condition of 

 the surface, do not encourage the use of motor trucks; and the development 

 of truck hauling, particularly for farm products, apparently has been held in 

 abeyance pending the construction of suitable road surfaces. About 90 per cent 

 of the tonnage of tratlic on Iowa highways is motor driven. 



The results of traffic weighings on a gravel surface indicates that the traffic 

 Is far beyond the capacity of a gravel road constructed with materials avail- 

 ble in Iowa. 



The use of electricity in agriculture, J. F. Ckowlet (Jour. Roy. Soc. Arts, 

 67 {1919), Xos. 34SS, pp. 605-701 ; 3.',89, pp. 709-721; 31,90, pp. 7 23-73 J,, Has. 15; 

 also in Cliem. News, 119 (1919), Nos. 3106, pp. 193-195; 3107, pp. 201,-206; 3111, 

 pp. 252, 253; 3112, pp. 26.',, 265; 3113, pp. 275, 276; 120 (1920), Nos. 3118, pp. 

 S5-28; 3119, pp. 37-1,0; 3120, pp. 1,9-52; 3121, pp. 66-68, figs. 15; abs. in Sci. 

 Abs., Sect. B— Elect. Engin., 22 (1919), No. 261,, p. 427).— This report deals with 

 the adaptation of electricity to different agricultural works, including lighting 

 and driving farm machinery, with special refex-ence to its develojiment in Ger- 

 many. It is stated that the most striking lesson drawn from a study of the 

 application of electricity to agriculture in Germany lies in the manner in 

 which the thinly populated rural district-s secured the advantages of a cheap 

 supply of electricity. This was done mainly through rural cooperative socie- 

 ties. Some of these societies produced electricity themselves ; some bought it 

 in bulk and distributed it over their own system ; while others combined to 

 guarantee a certain consumption and thus secured cheap current. 



The author is of the opinion that the conditions in England are such as to 

 make the provision of electricity in rural districts a much simpler undertaking 

 than in Germany, and that considerable progress would be made in the pro- 

 motion of a cooperative movement. It is stated that there are over 428,000 

 farms of from 5 to 300 acres each in the United Kingdom, and it is estimated 

 tliat to operate these electrically would consume not less than 4,000,000,000 

 units per annum. 



Belting for power transmission, E. D. Wilson (Trans, Anier. Inst. Chcm. 

 Engin., 11 (1918), pp. 237-21,5, flgs. //).— Tests of a number of belts made of 

 single-ply leather, 4-ply Balata, single and double solid woven cotton, 4-ply 

 friction surface rubber, and 4-ply stitched and filled canvas, are reported. 

 The belts were tested on 24-in. pulleys of cast-iron, steel, and wood at speeds 

 varying from 2,500 to 5,000 ft. per minute and tensions varying from 45 to 90 

 lbs. per inch of belt width. 



It was found that all the belts, with the exception of leather, exhibited the 

 same characteristics and showed inability to transmit power when slipping 

 about H per cent. The striking characteristic of all of the fabric belts is that 

 they pos.sess a very definite maximum capacity beyond which it is impossible 

 to go. Leather belting possessed an overloading capacity of GO per cent. It 

 was concluded that these experiments prove that the cheapest belting ma- 

 terial on a basis of the power actually transmitted is leather. 



Motor truck design and construction, C. T. Sciiaefkk (Xeic York: D. Van 

 Nostrand Co., 1919, pp. riII+318. figs. 292).— A compilation of data and prac- 

 tical information on the design and construction of motor trucks is given for 

 the use of the engineer. The following chapters are included : The general lay- 

 out of the chassis, the motor-truck engine — its construction and lubrication. 



I 



