XX ILLTJSTEATIONS 



FACING PAGE 



Plate 28 322 



Fig. 1, Leda Clays at Lewiston, Maine* From a photograph 



by L. H. Merrill. 

 Fig. % Beds of Volcanic Dust in Gallatin Co., Montana. 

 From a photograph by G. P. Merrill. 



Plate 29 838 



Fig. 1, Section of Glacial Till. From a photograph by G. F. 



Wright. 

 Fig. 2, Drift Bowlders in Walls of Glaciated Region. 



Plate 30 344 



Karnes near Whitewater, Wisconsin. From Professional 

 Paper No 34, TJ. S. Geological Survey. 



Plate 31 378 



Gullied Field near Marion, North Carolina. From Profes- 

 sional Paper No. 37, U. S. Geological Survey. 



FIGURES IN TEXT 



FI(S. PAGBJ 



1. Augite partially altered into Hornblende .... 36 



2. Mounted Thin Section of Rock 40 



3. Microscopic Structure of Museovite-Biotite Granite, Hallo- 



well, Maine 63 



4. Microscopic Structure of Diabase, Weeliawken, New Jersey 83 



5. Microscopic Structure of Peridotite (Porphyritic Lherzolite) 91 



6. Microscopic Structure of Pyroxenite 94 



7. Microscopic Structure of Oolitic Limestone .... 105 



8. Pyroxene partially altered into Serpentine .... 108 



9. Mierostrueture of Sandstone 114 



10. Section through Lake Basin, showing Bed of Diatom Earth 124 



11. Mierostrueture of Oolitic Limestone 126 



12. Mierostrueture of Fossiliferous Limestone .... 127 



13. Mierostrueture of Quartzite 137 



14. Mierostrueture of Crystalline Limestone .... 142 



15. Mierostrueture of Gneiss 143 



16. Rock Undermined by Windblown Sand .... 164 



17. Influence of Joints in the Production of Boulders . . 230 



