RURAL ENGINEERING. 589 



give such appreciable results on metaled roads with heavy vehicles and intense 

 traffic as on metaled roads with a moderate traffic, since the metiiled road itself 

 does not wear well under heavy vehicles and intense traffic. To obtain good 

 results it is not only necessai-y " to adopt a good system of surface tarring but 

 the roads on which it is done must be selected judiciously." 



Concrete highways (Philadelphia, 1913, pp. llJf, figs. 62). — This pamphlet 

 deals with tlie design and construction of concrete highways and with different 

 types of wearing surfaces. Specifications are included for 1- and 2-course pave- 

 ments, bitumen and sand wearing surfaces, and reinforced concrete pavements. 



The effect of salts upon the strength of concrete cured at low ajid normal 

 temperatures, II, E. Pulvee (Wis. Engin., 18 {1913), No. 1, pp. 6-13, figs. //; 

 abs. ill Cement Era, 11 {1913), No. 11, p. 4I). — Tests are reported which were 

 conducted to determine the effect of sodium chlorid and calcium chlorid sepa- 

 rately and together on a 1:2:4 concrete, cured at normal room temperature 

 and at temperatures below freezing. The salts were dissolved in the mixing 

 water in the following percentages by weight: Sodium chlorid G. 0, 12, and 15; 

 and calcium chlorid 2, 4, G, 8, and 10. 



The results show that the strength of the concrete cured under normal tem- 

 perature decreased as the percentage of sodium chlorid increased. For the 

 concrete cured at low temperature there was an increase in strength for the 

 addition of sodium chlorid up to 12 per cent after which tliere was a decrease. 

 The addition of calcium chlorid Increased the strength of this concrete up to 

 about 4 per cent at which point the maximum strength was reached. 



Serious disintegration was observed on the surfaces of cubes cured at low 

 temperatures and containing 6, 8, and 10 per cent of calcium chlorid. The 

 best effect was obtained at low temperatures b.y using both sodium chlorid and 

 calcium chlorid in the mixing water, a 2 per cent calcium chlorid and 9 per 

 cent sodium chlorid mixture giving the best results. 



Explosives in agriculture, F. R. Tbei^eaven (Queensland Agr. Jour., 81 

 (1913), No. Jf, pp. 201-204). — From the successful results of "experiments 

 carried out covering a period of the past eleven years ", the author briefly re- 

 views methods of using both nitroglycerine and chlorate compounds for land 

 clearing, subsoiling, log splitting, ditching, and drainage. He recommends the 

 chlorate compounds for the heavier blasting on account of their higher rending 

 and energy retaining powers. 



Electricity for the farm and home, F. Koesteb (New York, 1913, pp. XX+ 

 279, pi. 1, figs. 53). — ^This book includes the following chapters: Benefits of 

 agricultural electricity, central station service, generating electric power, elec- 

 tric motor applications, cost of operating, electricity in the manufacture of 

 farm by-products, electricity in the preservation of farm products, electric 

 transportation of farm products, electric plowing, diverse applications of elec- 

 tricity, electric heating, electric lighting, the telephone in rural communities, 

 electric power in irrigation, and electric stimulation of vegetation. 



Economics of rural distribution of electric power, L. E. Hildebband ( Univ. 

 Mo. Engin. Expt. Sta. Buh, // (1913), No. 1, pp. 50, figs. i2).— This paper is 

 primarily a discussion of the economic problems of the rural distribution of 

 electric power and is intended to be of interest to farmers, central station 

 managers, and engineers. It takes up in some detail the application and ad 

 vantages of electric power to farms, discussing these questions from the stand- 

 point of private and isolated generating plants on the one hand and rural di 

 tribution .systems on the other. Typical installations of both systems are de- 

 scribed and the fundamental, technical, and practical points to be considered 

 in the design and installation of a rural electric distribution system are out- 



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