686 EXPERIMENT STATION RECORD. 



theories of the foriuatiou of ground water, the interchange of surface and sub- 

 soil waters, the law of resistance to tlie motion of water through the ground, the 

 efliciency of different methods of obtaining a water supply, the determination 

 of the shape of the cone of depression of the ground-water surface by means of 

 experiments with pumps, and the determination of the discharge of a stream of 

 ground water tlirougli a given basin or cross section. 



Economic factors involved in road construction in strictly rural sections 

 {Hmjin. and Contract., Jf.l (IDi-'t), No. 11, pp. 2.7.5-2.58). — This article considers 

 the economics of country road construction from the standpoint of the general 

 welfare of the community, discusses the relative permanence of construction 

 and structural details, and describes methods of financing. 



It is considered fundamental that any outlay of money be made in such a 

 manner that it will result in a paying investment to the community. With this 

 in view it is concluded (1) that no road should be improved without some pro- 

 vision for its maintenance, (2) that all unprofitable work and works " de luxe" 

 be avoided within certain limits, (3) that all improvements not actually and 

 positively needed be omitted or postponed, (4) that the choice of kinds of pave- 

 ment the durability and ease of maintenauc of which have not been ascertained 

 in practice be avoided as much as possible, and (5) that unnecessary experi- 

 ments be avoided. 



The relation of farm produce hauling to permanent road improvements 

 (Engin. and Contract., }fi (1914), No. 9, pp. 215-217, figs. ,?).— This arti<-!e dis- 

 cusses economic questions relating to the classification of highways, hauling 

 radius, apportioning of aid. supporting areas of cities, and cost of distributing 

 food products, treating these subjects as fundamentals to economic road design 

 imder Ontario, Canada, conditions. 



Concrete highway bridge construction as standardized by Iowa commis- 

 sion, C. B. McCuLLOuGH (Eni/in. Rec, 10 (191-'f), No. 19, pp. ')l.'t-5n, figs. 6). — 

 The author, in describing the process by which the Iowa Highway Commission 

 has arrived at its standards for concrete highway bridges, states that topograph- 

 ical conditions markedly influenced the selection of designs for different parts 

 of the State. 



The cantilever type of abutment has been chosen for the general standard, but 

 to meet conditions of scarcity of concrete materials in the Kansan drift area 

 the pedestal or integral approach span type is being developed. The box type 

 of culvert is said to have proved in general the solution of the culvert problem 

 except in cases of very deep ravines requiring excessive fill, when the arch 

 culvert is used. 



Specifications and permissible stresses in material are given, and the standard 

 superstructure plans were designed for the following loadings: (1) Dead load- 

 ings of earth fill at 120, concrete at 150, and brick masonry at 150 lbs. per cubic 

 foot ; treated timber at 5 and untreated timber at 3^ lbs. per foot, board meas- 

 ure; and (2) a uniformly distributed live load over floor and sidewalk surface 

 of 100 lbs. per square foot or a concentrated live load consisting of a 15-ton 

 traction engine with weight on the rear axle of 20.000 lbs. and on the front axle 

 of 10,000 lbs., distance between axles 11 ft., distance between the rear wheels 

 6 ft, and width of the I'ear wheels 22 in. "Where the floor slab supporting 

 this concentration is relatively thin, as in the deck girder floors, each of the 

 rear wheels is assumed to distribute over an area 4 by 4 ft. Where the slab is 

 12 in. thick or over the lateral distribution is increased to 6 ft. for each wheel 

 or 12 ft. for the entire rear axle load, and the longitudinal distribution is taken 

 as 5 ft. The culvert loadings are taken the same as the foregoing with the addi- 

 tion that below 1 ft. the wheel load concentration is assumed to distribute 

 through the earth fill in four directions at the rate of ^ horizontal to 1 ver- 



