107. 



Lyon an. ;^in give the following relations between texture and 

 pore opaCf- for soils in field condition: 



by volume 



1. Clean sand 33 .W 



2. Coarse sand 40.00 



3. Medium smid 41. bO 



4. Fine snnd 44.10 

 I?. Sanely loasa i?'l00 



6. Fine sr-ndy loaiL >0.00 



7. Cilt loom ^3- 00 



8. Clav loam . 



. Clf?.y .00 



10. "Gunsbo* clay 58.46 



11. Heavy clay 47.19 



12. Very horr/y cl; 6^.12 



5on for the ^re' ter porosity of the finer soils appears 

 to be, that the smallest particles are so li&ht that they do not settle 

 so closely together in proportion to their &&& aiae a& do the sand par- 

 ticlee, becnusrr of the greater friction between their surfaces. Mien 

 thia i overcome by mixing in wattr, such material becomes uena. Xrea% 

 ment grontl. ta th Qtructure ana therefore the porosity of the 

 coil. 



m*ter of tlie individual pore spaces id of importance, a* 

 1 ns the total volume of pore apace, sine theae determine the cr pa- 

 city o: oil to retain and r&ove water and to permit the? circulation 

 of gnr: i the soil maas, as well as to facilitate the extension of tfee 

 " ; nt root;-. 



best arrangement of the soil is that of "crumbs". There are 

 veral possible arrangements of the soil particles, belonging to the 

 folio 2 ;>.i forme.: 



i; In columnar order, with each particle 

 ite ncigiibors at oniy four points. I'ho 

 unocc . or pore space is 47.64> of the total 

 volume occ 



In oblique order, with each particle 

 touching i Labors at six points, t^ie pore 

 space is 2t>.9b, of the total volume. 



3) Vheo^ spheres ma> be gati^ered into 

 larger spheres vshich r^-at together in the 



oecon r. Tlie pore space ia greatly increased, 

 ing 74. 



4) On Uie otaer hand, if there ore 

 spheres of several sizes so that Uie small ones 

 may rv;at in the spaces between the lar^e ones, 



1 pore spaco will be reduced below 2>.9: 

 and the spaces may continue to te filled in by 



spheres until the mass is practically 

 soliu, without pores. 



It is of course re cognised that under field conditions these 

 iderl nrrangemento do not pertain, but these figures illustrate the 



