VIII HOW CROPS FEED. 
CHAP Ti R at. 
ORIGIN AND FosMATION OF SOILS... 2.4.5. .:5 5.22 .se pes dun oe 106 
§ 1. Chemical Elements: of Rocks 52. 2..5.0 occ <cc 0» 2 sieee'enuh nee ee 107 
§ 2. Mineralogical Elements of Rocks) .42:.0.22 Get « sow eo eet eee 108 
§ 8 Rocks, their Kinds and Characters. ...... ..2..00. ssssme sees seen 117 
§ 4. Conyersion of Rocks into Soil 2..... jis. <2 5c o ewe openly ee tea 122 
§ 5. Incorporation of Organic Matter with the Soil, and its Effects....... *...135 
CHAPTER: PIL 
Krinpbs oF SoILs, THEIR DEFINITION AND CLASSIFICATION. 
§ 1. Distinctions of Soils based upon the Mode of their Formation or Deposi- 
§ 2. Distinctions of Soils based upon Obvious or External Characters....... 146 
CHAPTER IV. 
PHYSICAL’ CHARACTERS OF THE) SOD; 2.5.22: «s,s /clgyis onan tee eee thee 
§ 1. Weicht of Soils... 2. ...02. 20. ..s daclis ss Sey cape ee 158 
§ (2. State.of Divisions. 033,255. ease aa eee eee eee OS en Ce 159 
§ 3. Absorption of. Vapor of» Water. 2.0 o..020 200 lc coc os one eee 161 
§ ‘4. Condensation of Gases... . 2... 2 eee ka) eels anneal ieee eee 165 
§ 5. Power of Removing Solid Matters from Solution...............-+-2+++ +: 171 
§ 6. Permeability to Liquid Water. Imbibition. Capillary Power........... 176 
§ 7. Changes of Bulk by Drying and Frost........... 22.2 seceeeee cece cece: 183 
§ 8. Adhesiveness. ... 2.0 cc 0s. cece cece nacue ed. sweels ce) acetate ae 184 
§ 9. Relations to Heat... 2. .....6. sec cence ewelced seve obs sles es semis enna 186 
CHAPTER oF. 
Tue Sor As A SouRCE oF Foop To Crops: INGREDIENTS WHOSE ELEMENTS 
ARE OF ATMOSPHERIC ORIGIN. 
§ 1. The Free Water of the Soil in its Relations to Vegetable Nutrition...... 199 
§ 2. The Air-of the Soil. oo 0... oe. oe oe ee ele ale ale eles ee ae 217 
§ 3. Non-nitrozenous Organic Matters. Humus.:.......... scceecesssseerene 222 
§ 4, The Ammonia.of the Soil. ..( 5.23602. 2.0 0.40 e 0s 000 3 <i eee 238 
§ 5. Nitric Acid (Nitrates) of the Soil...2.. 0... 5.2. Jo cee aceasta eee 251 
§ 6. Nitrogenous Organic Matters of the Soil. Available Nitrogen........... 274 
§ 7%. Decay of Organic, Matters... 2.2... 0.0)..2.00e0 «oe » beste ee eaeiee a 289 
§ 8. Nitrogenous Principles of Urine.... ..........2+.2cecececcne cree sesscnss 293 
§ 9. Comparative Nutritive Value of Ammonia-Salts and Nitrates............ 300 
