788 EXPERIMENT STATION EECOED. 



The tensile strength of a mixture of 1 part cement and 3 parts sand im- 

 mersed in sodium carljoiiate, sodium sul])liate, and sodium chlorid was decreased 

 0.7 per cent after 12 months and 2.7 per cent after 26 mouths and the com- 

 pressive strength was increased GO.l per cent after 12 months and decreased 

 17.2 per cent after 2G montlis. A similar mixture immersed in a solution of 

 sodium chlorid, sodium sulphate, magnesium chlorid, and magnesium sulphate 

 was considerably reduced in strength after 12 months and could be crushed 

 between the fingers after ^6 months. 



A mixture of 1 part cement to 1 part sand immersed in a solution of sodium 

 carbonate, sodium chlorid, and sodium sulphate increased in strength in all 

 cases except in tensile strength after 2G months. The same mixture immersed 

 in a solution of sodium clilorid, sodium sulphate, magnesium chlorid, and mag- 

 nesium sulphate exiierienced a decrease in strength in all cases except in tensile 

 strengtli after 12 mouths. 



Permeability tests on gravel concrete {Engin. Rcc, 70 {1914), No. 13, pp. 

 355, 356; aJ)s. in Indus. Engin. and Engin. Digest, 14 {1914), No. 10, p. 411). — 

 In tests made at the University of Wisconsin to determine the permeability of 

 concrete to water it was found that tlie proportions of mixture, time of mixing, 

 socpience of placing materials in the mixer, and method of curing are vital 

 factors w^hen an impervious concrete is required. It was also found that 

 permeability of lean concrete in a direction normal to the pouring is greater 

 than in the direction of pouring. 



Wooden gang mold for concrete posts, F. W. Ives {Farm. Engin., 2 {1914), 

 No. 5, p. 85, figs. 5). — ^The construction and use of this mold is described and 

 illustrated. 



Recent road improvements in Hawaii, M. J. Adams {Engin. Rec, 10 {1914), 

 No. 13, pp. 342^34 'h flU'^- 5)- — This article describes road construction in territory 

 where rainfall is excessive and where the soil is from G to S ft. in depth, over- 

 lying lava rock. After one and one-half years of service the puddled macadam 

 surface was covered with a bituminous carpet, using two grades of asphalt 

 and two grades of asphaltic oil. The design of culverts and bridges and the 

 necessary road construction equipment are also described. 



Hai-per's gasoline engine book, A. H. Vebrill {New York: Harper & Bros., 

 1914, pp. XX+292, figs. 226; rev. in Engin. News, 12 {1914), No. 21, pp. IO45, 

 1046). — This book is intended for mechanics, farmers, and automobilists. It is 

 written in popular form and takes up in tuni the construction of the engine, its 

 use at home and elsewhere, and its oi^eration and maintenance. 



Tests of substitutes for gasoline, J. A. Moykb {Power, 40 {1914), No. 16, pp. 

 569-572, figs. 4)- — Comparative tests of kerosene, alcohol, motor spirit, and 

 mixtures of kerosene and gasoline as substitutes for gasoline in a farm gas 

 engine are reported, the primary object being to determine the maximum power 

 and fuel consumption for each of the fuels used with and vrithout water 

 injection. 



The tests showed that the maximum horsepower of the engine is considerably 

 increased, especially with kerosene as fuel, but that the fuel consumption per 

 horsepower-hour is considerably greater with water injection. For purposes 

 of comparison similar tests were made with gasoline without water injection, 

 ■which shov\ ed that the fuel cost per brake horsepower-hour was greater in all 

 cases than with the other fuels. Tests with the so-called air injection devices 

 showed that the economy of tlie engine is considerably improved when air is 

 injected into the manifold. 



The cause of the so-called preignition in kerosene engines, which is dis- 

 tinguished by sharp pounding at the connecting rod, is said to be probably not 



