THE PHYSICAL PROPERTIES OF THE SOIL. 771 



Specific (/ravitif of soil constitiiciifs. 



Quartz 2. 622 



Clay 2.503 



Lime, carbonate crystalliuc 2. 756 



Lime, carbonate preciititatcd 2. 678 



Gypsum, precipitated 2. 318 



Oxid of iion 4. 54-5. 20 



Hydrated oxid of iron 3. 760 



Humus 1.462 



With these vahtes it is possible to calculate the density of any soil. 

 The more important minerals occurring in vsoil have the following 

 sx>ecific gravities:^ 



Sprcijic (jiaritii of different itiinerals. 



Feldspar 2.5 to2.8 



Orthoclase 2. 5 to 2. 6 



Olijioclase 2. 6 to 2. 7 



Calcite 2. 6 to 2. 8 



Dolomite 2. 8 to 3.0 



Chlorite 2. 7 to 3. 



Labradoritc 2. 6 to 2. 8 j Talc 2. 6 to 2. 7 



Augite 3. 2 to 3. 5 j Magnetite 4. 9 to 5. 2 



Hornblende 2. 9 to 3. 4 Limonite 3. 4 to 4. 



Mica 2.8to3.2 I Hematite 5.1to5.2 



Potash mica 2. 8 to 3. 1 



Magnesia mica 2. 8 to 3. 2 



THK VOIXMK WKKfHT OF THK (SOIL. 



This is also called apparent specific gravity, and is the weight of a 

 given volume of the soil compared with an equal volume of water. In 

 the specific gravity we are concerned only with the volume of the actual 

 solid matter of the soil, exclusive of the air or water that occurs in the 

 spaces between the particles; in the volume weight we consider the 

 soil as a whole, including the spaces occurring in it. 



According to the investigations of the author^ quartz has the highest 

 volume weight in the air-dry state (1.4485), humus the lowest (0.3349), 

 and clay a value intermediate between the two (1.0108). The volume 

 weight of soils, other things being equal, increases with the i)resence 

 of iron and stones. The volume weight of one and the same soil 

 depends on the mode of arrangement of the particles and is subject to 

 great variations. The more compactly the particles are arranged the 

 greater is the weight of the mass, when equal volumes are considered, 

 and vice versa. Under otherwise similar circumstances the coarser the 

 grains the higher the volume weight. A mixture of grains of different 

 sizes has a higher volume weight than a mass composed of grains of 

 the same size, large or small. By the formation of floccules in a soil, 

 its volume weight is decreased in proportion to the coarseness of the 

 aggregates formed. 



' G. Schiibler, Grundsiitze der Agriculturchemie, 1838, pt. II, p. 61. C. Trommer, Die 

 Bodenkunde, 1857, p. 258. A. von Liebenberg, Ueber das Verhalten des Wassers im 

 Boden, Inaugural-Dissertation, Halle, 1873. C. Lang, Forsch. Geb. agx. Phys., 1, p. 

 136. G. Amnion, Ibid., 2, p. 26. E. Wollny, Ibid., 8, p. 347. E. Ramaun, Forstliche 

 Bodenkunde, 1893, ji. 61. 



- Forsch, Geb. agr. Phys., 8, p. 349. 



