105. 



aeration, which helps smaller forms of life. 



A large amount of extremely fine silts in thes clay uoil gives 

 the putty soil, which differs from the pure clay both in composition 

 nnd in action with respect to site and plants growing on it. The par- 

 ticles are about 25 microns in diameter. 



Clay is very plastic, this "being a characteristic property, sin- 

 ce clay is * hydrous aluminum eilcate. This plasticity is restricted to 

 particles of very small size; n. plastic clay will not hold 8 inches of 

 water in 24 hours. The addition of salt ( ImCl } will flocculate clay. 

 Sodium carbonate (l\a 2 COo) will prevent f locculr>tion cf clay. 



Further information in regard to clay and its properties may be 

 found in references on Soils as mentioned nbove, arm also in Bulletin 

 388, J, .Geological G-urvey, entitled: The Colloid Matter of Clay and its 



ent . 



ci. \Veight of Ciils. is 



The average specific gravity of rocks about 25 Heavy rocks 

 contain iron. Soils have half the volume weight of the soil rocks. In 

 other words, they are half rock and half atmosphere. 



The weight of soil is the result of two factors: the absolute 

 specific gravity, and the volume of pore space in the mans. An average 

 specific grnvity of r.oil material is often Accepted ^s 2.65. The weight 

 of n givcm volume of soil may be determined from the pore space and spe- 

 cific gravity of the materials, by use of the following formulae: 



.1) V/3 * Jw x (2.65' x (100 ~ \. 



Where vvs * Height of given volume of soil 



/v; = Weight of volume of water equal to volume tff soil 



P r Per cent of pore space 



(100 - P) a Per cent of volume occupied by soil 



2) Or the following formula may bs used, and is often more 

 convenient : 



We * Ap.Sp. x Ww. 

 -re WB r height of soil 



Ap.Sp. Apparent specific gravity 



Ww r v.eight of volume of water equal to that occupied by 

 the r>oil. 



Following ia a table of weights of a few soils: 



Vol.Wt. ft. per Wt.per 



Soil or apparent cu.ft. acre-ft. 



Sp. Gr. 



1. Clean sand l.?6 110. 0# 4,800,000 # 



2. Coarse sand 1.60 100.0 4,3^6,000 



3. 'odium sand 1.J4 96.0 4,200,000 



4. Fine s*nd 1.48 93-0 4,o60 t OOO 



5. Sandy loam 1-30 61.0 3.5!?Q,000 



6. Pine sandy loam 1.32 82.5 3.590,000 



7. Silt loam 1.24 77-5 3,400,000 



8. Clay loam 1.22 7^.0 3.330,000 



9. Clay 1.17 72.6 3,150,000 

 10. "Gumbo" clay 1.10 Ou.i>' 3,000,000 



--Lyon and .Pippin. 



