C; libration of the - 13 - D. M. Poole and 



Emery Settling Tube W. S. Butcher 



for Sand Analysis 



with coarse sands some sliimping may occur* The inaccuracies in reading the 

 sand height due to the rapidly changing interface, plus the error due to slump- 

 ing, indicate that the settling tube should not be used in analyzing samples 

 containing an apprecicble amount of coarse sand. 



Summsry 



The tLme saved making mechanical analyses of sand by means of the settling 

 tube contrasted to sieving has already been pointed out by Emery (I938). This 

 paper shows that the probable error of analysis is about the same for both 

 methods, if the particles greater than 1 mm. rjid less than I/I6 mm. (if more 

 than 5^ of total sample) are removed before running a sample through the set- 

 tling tube. The settling tube analyses have also been shown to be reproducible 

 with a percentage probable error of 0.8 (settling tube error). The error due 

 to splitting the sample to the correct size (splitting error) for use in the 

 settling tube is undetermined at present. The Jones type splitter may be used 

 alone, or the "Otto Microsplit" may be used after the srmple has been split to 

 a weight of about 20 - 25 grams. 



Acknowledgments 



Acknowledgment is made to Mr. D. L. Inman for his constructive suggestions 

 during the course of the investigation and his critical reading of the manu- 

 script. Dr. F. P. Shepard kindly read and suggested improvements in the manu- 

 script, Mr. J. C. Ludwick, Jr., allowed the use of unpublished data collected 

 by him and discussed the problem constructively with the writers. Mr. D. B. Say- 

 ner is to be thanked for drafting the several diagrams. 



