1919] RURAL ENGINEERING. 383 



monolithic concrete Is developed. Roughening of the old concrete or treatment 

 with dilute hydrochloric acid increased the bond strength by 20 per cent, as 

 did also a bonding medium of a thin layer of neat cement butter. Tamping the 

 fresh concrete hard against the old concrete increased the bond strength 5 

 per cent. 



With reference to shearing strength, it was found that the strength of a 

 joint was greatly increased by treatment of the surface of the old concrete. 

 It was further found that there was no danger of leakage at a joint made in 

 concrete of a mixture as rich as 1 : § : IJ under pressures up to 40 lbs. per 

 square inch when the surface of the old concrete had been treated. 



The results of tests by others, bearing on the subject, are also reviewed. 



[A total of 6,146,617 motor vehicles in the United States], A. P. Anderson 

 iU. S. Dei)t. Agr., Public Roads, 1 (1919), No. 11, pp. 8-16, fig. i).— Data are 

 given covering registrations, licenses, and revenues in the United States dur- 

 ing the calendar year 1918. 



A total of 6,146,617 motor cars and commercial vehicles and 240.564 motor- 

 cycles were registered in 1918 in the 48 States and the District of Columbia. 

 Registrations and license fees, including chauffeurs, operators, and dealers, 

 amounted to a total of $51,477,416.61. These figures do not Include about 

 107,000 automobiles and motor trucks manufactured for the Government 

 during the year. As compared with 1917 the data for 1918 represent an in- 

 crease of 19 per cent in the number of cars and 27 per cent in revenues. 



Motor transportation for rural districts, J. H. Collins (U. 8. Dept. Agr. 

 Bui. 770 {1919), pp. S2, figs. 5).— This bulletin reports in general the results of 

 preliminary studies of rural motor routes established, or in process of estab- 

 lishment, with the purpose to call to the attention of operators and prospective 

 operators those features of the industry which apparently are not understood 

 or appreciated. 



It was found that there are five general classes engaged in rural haiiling 

 on a schedule basis as follows: (1) The farmer who hauls for his neighbor 

 or for the community as well as for himself, (2) the regular local truck oper- 

 ator with limited capital, whose income is derived largely from the business, (3) 

 local automobile or truck agencies operating as a side-line, (4) city transfer 

 companies, and (5) large corporations operating a fleet of trucks and com- 

 manding considerable capital. It was found that the four important factors 

 which must be considered by the beginner in the field of rural motor transporta- 

 tion are (1) the volume of farm products produced along the contemplated 

 route, (2) the volume of miscellaneous hauling which can be secured to supple- 

 ment regular loads, (3) competition with other carriers, and (4) the character 

 of the highways. "Above all, attention should be concentrated on the problem 

 of arranging for loads so that there is a profitable load on all trucks when- 

 ever they are operated." It is stated that in considering competition particular 

 attention should be given to rates, schedules, and delivery arrangements. Good 

 roads are considered a prerequisite to successful motor truck operation. 



With reference to certain operating costs, it was found that the gasoline 

 mileage for trucks of different sizes showed a very wide range under varying 

 conditions. Data from about 60 typical motor routes showed from 5 to 9 miles per 

 gallon of gasoline for 2-ton trucks, 4 to 6 miles for 8-ton trucks, and 3 to 5 miles 

 for 5-ton trucks. Drivers' wages varied from $2.75 to $7.50 a day. Deprecia- 

 tion was estimated by operators at from 20 to 33^ per cent of the cost of the truck 

 annually. The annual average interest on the investment was calculated by 

 A 4-1 C VTJ 



the following formula: —r~'^~2 — ^^^^^^^S© yearly interest. In this formula 

 A represents the estimated life of the truck in years under actual operating 



