486 EXPERIMENT STATION RECORD. 



lu flume construction it is considered advisable usually to erect a small saw- 

 mill to saw out the lumber needed for construction. An accurate and careful 

 survey of the proposed line of flume construction is considered a prime necessity,' 

 particulai'ly as regards grades and curves. In general, the lowest grade con- 

 sidered satisfactory for successful operation is about 1 per cent, and the most 

 satisfactory results are obtained when the grade is from 2 to 10 per cent, with 

 a maximum of 15 per cent. The degree of curvature should be kept as low as 

 practicable with a usual maximum of 20°. Where the topographic conditions 

 in a locality are such that abrupt curves in the flume are absolutely necessary, 

 it is considered advisable to reduce the length of the boxes, and correspond- 

 ingly shorten the distance apart of the bents, arms, and braces, and to Increase 

 or raise the height of the V on the outside of the curve. The most satisfactory 

 distance between bents is said to vary from 12 to 16 ft., according to the 

 capacity of the flume and the use to which it is to be put. " Flume construction 

 should usually be strongly reinforced at those points from which it is con- 

 templated to do extensive shipping or where such material is to be loaded into 

 the flume over the side." 



Other general information is given regarding feeders for maintaining the 

 required amount of water, tunneling, small holding reservoirs at different 

 points of flume, reservoir ponds at the head of flumes, branch flumes, switches, 

 the use of telephones in flume operation, and cost of construction of flumes. 

 Tabular data on the weight of water in a 16-ft. section of flume when filled to 

 various depths, amount of water required to fill flumes, and velocity of water 

 in flumes when filled to various depths at different grades, and estimates of the 

 approximate amount of material required, for the construction of typical flumes 

 are giA^en. 



The use of coordinates in surveying and laying out tracts for irrigation, 

 H. H. Logan {En gin. Ncios, 71 {191Jt), No. llf, pp. 738-740, fig. i).— This method 

 is described and illustrated. 



Soil porosity and the distance between drainage channels, L. Schmeer 

 (Engin. and Contract., 41 (1914), No. 13, pp. 398, 399, figs. 2).— The author, by 

 means of formulas and tabulations, deduces values of the transmission con- 

 stant for soils, noted in previous work (E. S. R., 30, p. 289), as modified by 

 humus in the top layers of the soil. 



The road drag and how it is used (U. 8. Dept. Agr., Farmers' Bui. 597 

 (1914), Pik- 15, figs. 8). — The purpose of this paper is to describe the best meth- 

 ods of constructing and using road drags and to supply information concerning 

 the conditions for which such drags are adapted. The principal points dis- 

 cussed are summarized as follows: 



The road drag is the simplest and least expensive contrivance yet devised for 

 maintaining roads constructed of earth or earthy material. Its successful oper- 

 ation depends to a very great extent on the skill and intelligence of the oper- 

 ator. The time to use the drag is when the material composing the road sur- 

 face is sufficiently moist to compact readily imder trafiic after it has been 

 moved by the drag and when it does not contain sufficient moisture for the 

 traffic following the drag to produce mud. Dragging can not usually be so 

 arranged as to keep teams employed all the time, making it desirable to have it 

 done by interested persons who are otherwise employed when not engaged in 

 dragging. 



It is further pointed out that the road drag is essentially a maintenance 

 implement, that its use in construction is distinctly secondary, and that roads 

 which are very rocky or very sandy can not be materially improved by its use. 



An outfit for boring taprooted stumps for blasting, H. Thompson (U. S. 

 Dept. Agr., Farmers' Bui. 600 (1914), pp. 5, figs. .^).— This publication gives 



