1919] RURAL ElvrGi:N"EERING. 787 



" The percentage of absorption obtained by immersion in water below the 

 boiling point increases as the temperature of the immersion water decreases. 

 This is true both in cooling after the boiling test and in the regular immersion 

 test. The variation in the percentage of absorption due to this cause is usually 

 noticeable, but it is not in constant ration to the temperature change and is 

 nearly always small ; it is large enough, however, to make it advisable that the 

 temperature of the water in all absorption tests should be specified. 



" The principle does not apply to immersion in boiling water. It was found 

 that there is a definite and fairly constant ratio between the results of the 

 recommended standard boiling test for determining absorption and those of the 

 absorption test by 72 hourjs' complete immersion in water at room temperature. 

 The average of a large number of determinations made in this investigation indi- 

 cates that for Iowa shale tile the percentage of absorption by the recommended 

 standard boiling test is approximately 1.4 times that after 72 hours' complete 

 immersion in water at room temperature. The boiling absorption test is to be 

 preferred to the immersion absorption test. The boiling absorption test has 

 been adopted as standard for draintile by the American Society for Testing 

 Materials, and all absorption tests of draintile should be made in strict compli- 

 ance with sections 21 to 2.5, inclusive, of the ' Standard Specification for Drain 

 Tile.' 



" In these tests, as in many others, it was found in general that the strength 

 increased as the absorption decreased. This relationship was clearly apparent 

 in the case of tile with widely different strengths and absorptions, but was 

 obscured by other factors where the range in either strength or absorption was 

 small. It is now very generally recognized that draintile from several factories 

 can not be judged correctly by a single color standard. It is almost as generally 

 believed that the product of a single plant, while using the same methods and 

 similar clays, may be judged correctly by color. This is upon the assumption 

 that, with the same clays treated in the same manner, the quality of the product 

 will depend upon the burning, and that this will be indicated very clearly in two 

 cases, that this rule will not apply even to the product of a single factory unless 

 the full history of the manufacture of the product is known and considered. 



" The best method for making freezing and thawing tests of draintile is that 

 prescribed in sections 26 to 31, inclusive, of the Standard Specifications for 

 Draintile of the American Society for Testing Materials. The above method is 

 similar to that used in the ' final ' artificial freezing and thawing tests reported 

 . . . and produces much more decisive results than those obtained In 'pre- 

 liminary ' tests. Sodium sulphate tests by the ' recommended method ' developed 

 in this investigation gave results approximating those obtained by three times 

 as many standard freezing and thawing tests." 



The sampling' of deposits on road stone and gravel in the field, L. Reinecke 

 and K. A. Claek {Amer. Soc. Testing Materials Proc, 18 {1918), pp. 393-415).— 

 This is a preliminary report on a series of studies upon variations in the road- 

 making qualities of deposits of bedrocks, bowlder aggregates, and gravel. 



The investigations on bedrock showed that " the results of an abrasion test 

 expressed as percentage of wear are liable to an error of 0.2 per cent due to 

 variations caused by laboratory procedure. No additional error is introduced 

 into the results of abrasion tests by the process of sampling when samples 

 are collected in the manner outlined. Results of abrasion tests on rock in 

 place in a deposit represent, within a probable difference of 0.4, the per- 

 centage of wear that will be shown by a crushed product produced from the 

 deposit. In the case of deposits consisting of stone of a very uniform char- 

 acter and appearance, the results of abrasion tests on samples taken at one 

 153351°— 20 7 



