The practical implication from these correlations" is that particle spacing and 

 bulk density possibly may be used as a substitute for X or to estimate X in other 

 fuels as well as those studied. Measurement of X entails considerable work because 

 knowledge of fuel surface area and volume is required for its computation. In many 

 fuels, it would be easier to determine spacing by actually sampling the distances be- 

 tween particles or by counting the number of particle intersections with a sampling 

 plane. Bulk density can be determined readily by measuring fuel weight and dimen- 

 sions of the fuel complex from a sample of plots. It is uncertain which of the three 

 properties--bulk density, particle spacing, or ^--provides the most accurate descrip- 

 tion of porosity. Perhaps more accurate expressions of porosity than these three can 

 be developed. 



14 



