ILLUSTEATIONS ^xi 



^<5. PAGE 



18. Exfoliation of Granite, Stone Mountain, Georgia . . , 231 



19. Concentric Exfoliation of Granite, Canada .... 232 



20. Microstructure of Sandstone, with Large Absorptive Power 256 



21. Microstructure of Diabase, with relatively Little Absorptive 



Power 256 



22. Flint Implement showing Weathered Surface .... 261 



23. Sketch showing Pre-Palseozoic Decay of Rocks . . . 263 



24. Diagram showing Direction and Rate of Motion of Soil . 275 



25. Diagram showing Flood Plain of River .... 277 



26. Angular Outlines of Particles in Residual Soil from Gneiss . 289 



27. Section across Central Kentucky, illustrating Inherited Char- 



acteristics of Soils 291 



28. Angular Quartz Particles from Decomposed Gneiss . . 292 



29. Outlines of Kaolinite Crystals and Kaolin Particles . . 297 



30. Section across Small Lake 302 



31. Talus Slopes 308 



32. Alluvial Plains 311 



33. Outlines of Particles in Chinese Loess 317 



34. Particles washed from Leda Clays 323 



35. Cross-section of Marine Marsh 326 



36. Quartz Granules in Beach Sand 331 



37. Outlines of Particles of Glass in Volcanic Dust . . .337 



38. Section through Carboniferous Soil 376 



39. Section showing Varying Character of Residual Soil . . 377 



40. Section through Ant Nest ....... 379 



41 and 42. Sections showing the Effect of Tree Roots in Soil . 384 



Fig. 1, after G. W. Hawes; 5 and 6, after G. H. Williams; 16, after 

 G. K. Gilbert; 18 and 22, after Robert Bell; 10, 23, 24, 26, 29, 30, 31, 34, 

 37, 38, 39, 40, and 41, after Shaler, Twelfth Annual Report United 

 States Geological Survey, 1890-1891. 



