KURAL ENGINEEEING. 891 



Roads of this Department for cement concrete with bituminous surface, oil 

 cement concrete, cement, gravel, crushed limestone, and crushed trap rock for 

 road construction are presented. 



A highway bridge in detail (Cement Era, 10 {1912), No. 10, pih 30, 31, 

 figs. 2). — Working plans and specifications are given of a novel combination of 

 steel and reinforced concrete in a double span highway structure with rein- 

 forced concrete abutments and piers, and reinforced concrete floor supported on 

 steel I-beam girders. The estimate shows 30,491 lbs. of steel and reinforcing 

 and 267A cubic yards of concrete for the 56 ft. structure. 



Influence of moisture on the expansion and contraction of concrete 

 {Engin. Rec, 66 (1912), No. Ui, pp. 315, 576).— This is an abstract of a paper 

 read by L. W. Page before the Ohio Engineering Society in which he gives the 

 results and conclusions of investigations of the cracking of concrete, especially 

 in road construction soon after completion, due to the inherent contractive 

 qualities of the concrete mass in hardening. 



The results show that the contraction and expansion vary with the strength 

 of the mixture, which is a cause for shearing action and separation of the rich 

 top coat from the leaner base mixture in concrete pavements. They further 

 show that if during a period of 6 months the temperature of a concrete mass 

 falls 100° F., each inch of length will contract 0.00055 in. ; that if the mass 

 dries, each inch will contract 0.00OG8 in. ; and that there is a further contrac- 

 tion due to the subsequent loss of heat brought about by the chemical action 

 of the cement. In a 100 ft. concrete roadway the contraction might be as much 

 as Ih in., which brings about an enormous tensile stress causing cracking and 

 breaking up of the jiavement. 



[A selection of farm power], Strecker (Maschinen Ztg., 10 {1912), No. 16, 

 pp. 185-192, figs. Jf). — This is a discussion of the farm power question, making 

 comparisons of the costs of power by electricity, internal combustion engines, 

 and steam. Tables showing cost data are given for all three, with a table of 

 comparative cost data, showing that economy in farm power depends on the 

 use to which it is put. the amount required, the length of time it is to be used, 

 and the local prices per unit of power. When from 8 to 20 horsepower are 

 required for au average of 200 working hours or less per year, electricity is 

 considered the cheapest, but when from 8 to 20 horsepower are required for 

 from 600 to 1,500 working hours or more per year the data indicate that 

 internal combustion power is the cheapest with steam and electricity alternating 

 for second place in cheapness. 



Electricity on the farm, P. A. Bates {Neiv York. 1912, pp. 1661-1679, pis. 

 12, figs. 3). — This is a pai>er presented at the twenty-ninth convention of the 

 American Institute of Electrical Engineers in which the author discusses the 

 application of electricity to irrigation and drainage pumping and to farm light- 

 ing and machinery driving, describing several installations and ix)inting out 

 their economic advantages. He discusses public service electric lines and farm 

 cooperative systems, and states that where neither of these is feasible a small 

 private system of lighting may be installed for approximately $250, and that 

 more power as needed may be generated at reasonable cost. He encourages the 

 use of electricity for lighting, heating, and power because of the great safety 

 from fire. 



Electricity in agriculture, A. Vietze (Ar&. Landiv. Kamnier Prov. SacJisen, 

 1911, No. 22. pp. Ji2, figs. 18). — This pamphlet discusses the farm electric iwwer 

 and light movement with special reference to installation and relative economy 

 of cooperative and central electric farm plants and public service systems, 

 makes comparisons with other sources of power and light, and outlines the 



