290 EXPERIMENT STATION- RECORD. 



Concrete Road Building bearing on standard practices in concrete road con- 

 struction includes recommendations as to specifications, construction, mainte- 

 nance, and cost. 



The contraction and expansion of concrete roads, R. J. Wig, N. H. Tunni- 

 CLiFF, and W. A. McIntyre {Abs. in Engin. and Contract., 4I {1914), ^0. 8, 

 pp. 257-262, figs. 4; Engin. News, 11 (1914), ^o. 9, pp. 446-449, fig. J).— Ex- 

 perimental data are reported relating to the effect on expansion and contrac- 

 tion of concrete in concrete roads of changes in the temperature and variations 

 in the moisture content of the concrete, variation in the condition and character 

 of the sub-base, and excessive loading by traffic. These data " indicate that the 

 effect of moisture content is very much greater than the effect of temperature 

 change, and may be sufficient to cause a stress in the concrete opposite to that 

 which would be caused by a normal temperature change. A variation in the 

 quality of the concrete will cause a variation in the tendency to expand and 

 contract with change in moisture content." 



It is concluded that a proper combination of change in temperature, change in 

 moisture content, and friction have made possible the construction of long slabs 

 which have remained free from cracks. " With a proper understanding of the 

 physical phenomena . . . and a proper application of engineering principles it 

 is believed . . . that all expansion and contraction of concrete in roads can be 

 so controlled as permanently to avoid craclving." 



Desig'n of reinforced concrete, C. Aubrt (Calcnl du Beton Arme. Paris, 

 1913; rev. in Sci. Amer., 110 (1914), No. 8, p. i68).— This is a compilation of 

 formulas, tables, and diagrams in compact form for use in designing and esti- 

 mating reinforced concrete. 



Concrete destruction by ground water containing sulphates (moor water), 

 ScHEELHAASE (A&s. in Wttsser u. Abwasser, 7 (1914), ^P. 11, p. 4^4)- — Investi- 

 gations on the effect of moor water on concrete led to the conclusion that water 

 containing gypsum, such as moor water, is able to destroy concrete, this de- 

 struction being produced by increase in volume. The effect on concretes made 

 from different makes of cement was entirely different and the age of the con- 

 crete had little Influence on the processes of destruction. Concrete made with 

 certain cements was not destroyed. 



How to calculate the losses in gas engines, G. W. Muench (Power, 39 

 (1914), ^^0. 7, pp. 248, 249). — Simple calculations are given showing how to 

 figure the heat balance of a gas engine with a degree of accuracy which is con- 

 sidered close enough for ordinary purposes. 



Notes on power variation with atmospheric changes, H. Chase (Oas 

 Engine, 15 (1913), No. 11, pp. 627, 628).— Tests of an internal-combustion 

 motor showed appreciable power variations with marked changes in barometric 

 pressure. 



Power losses due to tardy ignition, R. Trautschold (Oas Engine, 15 (1913), 

 No. 11, pp. 604-607, fig. 1). — The author points out by data, curves, and dis- 

 cussion that tardy ignition in an internal combustion engine decreases the power 

 output by reducing the mean effective pressure and by causing inefficient expan- 

 sion of the products of combustion In the engine cylinder. 



Elementary machine design, W. C. Marshall (New York and London, 1912, 

 pp. VIII+320, pla. 3, figs. 193; rev. in Science, n. ser., 39 (1914), No. 999, p. 

 288). — This is a book of information and instruction on machine details, and 

 is intended for students who have not studied mechanics and mechanism, 

 although considered to be of service to draftsmen who are already familiar 

 with the principles and methods of machine design. It contains chapters on 

 machine drawing, rivets and riveted joints, piping, screws and bolts, shafting 



