86 EXPERIMENT STATION RECORD. [Vol. 43 



to give results which will check within 0.4, or 10 per cent, of the range in 

 coefficient of wear of granite block. The maximum range in coefficient of wear 

 by the modified method, and including tests of good fresh stock from practically 

 all of the coumiercial quarries, was from 6.5 to 10.5. Discoloration of granite 

 block is not necessarily an evidence of disintegration. Disintegration which 

 has progressed far enough to render the block unsuitable for paving purposes 

 may be readily detected by means of the abrasion test. In order to place the 

 question of tests of granite block on a definite basis, the author recommends 

 that in the future specifications for quality include the one requirement of 

 coefficient of wear, and that this value be determined by the modified abrasion 

 test mentioned above. 



An apparatus for determining the consistency of concrete, F. L. Roman 

 (Engin. and Contract., 53 {li)20), No. 9, pp. 240, 2^1, fig. 1). — A number of ex- 

 periments, conducted by the Illinois State Highway Department, are reported, 

 from which it was found that an apparatus consisting of a truncated cone 12 

 in. high with 8 in. inside diameter at the base and 4 in. inside diameter at the 

 top, will give results as regards consistency of concrete superior to all other 

 truncated cones investigated. The truncated cone obtained was far better than 

 a cylinder for determining the consistency of concrete by means of a slump test. 



Concrete blocks: How to make and use them {Concrete Utilities Bur. 

 [Pamphlet^, No. 12 [1919'\, pp. 17, figs. 17). — Brief popular information on the 

 manufacture and use of concrete blocks is given. Drawings of equipment for 

 manufacture are included. 



The proper balancing of fuel, lubricant, and motor, W. F. Parish {Mech. 

 Engin. [New TorA-], 42 {1920), No. 3, Sect. 1, pp. 164-168, 193, figs. 8).— This is 

 a study of the dilution of lubricating oils in internal combustion engines, 

 especially for vehicle propulsion, by the fuel mixture, the purpose being to 

 show the resulting losses of fuel, power, and lubricant. 



Heat flow through cylinder Avails, L. Illsier (Trans. Soc. Automotive 

 Engin., 13 {1918), pt. 1, pp. 162-195, figs. 9).— The results of research into the 

 speed limitations imposed upon high-duty internal combustion engines by ex- 

 cessive heat flow through the cylinder walls are reported. 



It is pointed out that excessive heat flow raises the temperature of the bore 

 and head walls unduly, resulting in lubricating and cracking troubles. It is 

 shown that lai'ge bore engines reach their limiting bore temperatures at com- 

 paratively low rotative speeds, and that large high-speed engines are likely 

 to suffer seriously from destructive heat flow effects. The determining factors 

 which control heat flow are shown to be temperature, rotative speed, and rela- 

 tion of volume to cooling surface. Formulas are presented for the quantitative 

 determination of heat flow, and a method is developed for critical analysis 

 of the design characteristics of any normal gas or oil engine for heat flow 

 effects. From a study of speed limits taken of numerous engines in various 

 kinds of service, the desirable bore temperature limit was found to lie between 

 400 and 450° F. The combined temperature and pressure stress set up in a 

 cylinder wall is analyzed, and fornmlas are deduced for its estimation. Other 

 factors are discussed. 



Report of the Inter-Departmental Committee on the employment of gas 

 as a source of power, especially in motor vehicles in substitution for 

 petrol and petroleum products, B. Redwood {London: Govt., 1919, pp. 35, pis. 

 11, fig. 1). — This is the report of a committee appointed in 1917 iii England to 

 investigate (1) the substitution of gas for petrol and petroleum products as a 

 source of power, especially for traction purposes, and (2) the manner in which 

 such gas may be supplied, stored, carried, and used with convenience and safety. 



