15. Size Analysis - sample size fraction values are based on dry- 

 weight and given in ^h±{(^) units to the nearest whole percent. 

 An American Instrioment Company sieving machine and U. S. Standard 

 sieves are used for determining sand and larger size fractions. 

 The pipette method of analysis was used for determining the silt 

 and clay fractions. 



QD^ - (phi quartile deviation) - is that statistical parameter 

 which is a measure of one half of the spread of the quart iles 

 and is expressed in phi units to the nearest tenth with the 

 given value computed from the formxila: 



QDo( = ^ M 



2 



SKj^ - (phi quartile skewness) - is that statistical parameter 

 which is a measure of half the sum of the first and third quartile 

 values less the median and is expressed in phi units to the near- 

 est hundredth with the given value computed from the formula: 



SY.4 = 3i^ + U - Md^ 

 2 



MD^ - (phi median) - is the middlemost member of the distribution 

 curve above which 50 percent of the diameters in the distribution 

 are larger and below which 50 percent of the diameters are sriialler 

 and is expressed to the nearest tenth of a phi unit. 



The following table is presented for the conversion of phi units 

 to millimeters: 



Phi (iz() Millimeters 



-2 4.0 



-1 2.0 



1.0 



1 0.50 



2 0.25 



3 0.125 



4 0.0625 



5 0.0313 



6 0.0156 



7 0.0078 



8 0.0039 



16. Wet Density (ibs./ftP) - density measured to the nearest tenth 

 of a pound as determined by means of a "Mudwate" hydrometer. 



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