ILLUSTRATIONS 



Restorations of: A. the hypothetical proavian, B. the 



toothed bird Arch&opteryx Frontispiece 



Plate I. A. Nebulosity in the Pleiades. B. Spiral nebula in 



Ursa Major facing page 8 



Figure 1. Diagram to illustrate tidal forces 14 



Figure 2. Origin of a spiral nebula according to Chamberlin 



and Moulton 18 



Plate II. The western and eastern hemispheres facing page 40 

 Figure 3. Diagram showing the times and probable extent of the 



more or less marked climatic changes in the geologic 



history of North America, and of its elevation into 



chains of mountains 53 



Figure 4. Glacially striated diabase, made in early Permian 



time. South Africa facing page 54 



Figure 5. Lower Cambrian quartzite, striated in early Permian 



time. South Australia .... facing page 54 

 Figure 6. Glacial bowlder beds beneath thick formations of 



dolomite on the upper Yangtse River, China. Age 



of till, late Proterozoic .... facing page 56 

 Figure 7. Eroded exposure of the oldest known glacial deposits 



(Lower Huronian), near Cobalt, Ontario 



facing page 56 

 Figure 8. Striated bowlder taken from the oldest known glacial 



deposits facing page 56 



Figure 9. Generalized map of North America in Paleozoic time 62 

 Figure 10. The marine inundation in Pennsylvanian time . . 66 

 Figure 11. Earlier and maximal phases of the Silurian flood . 72 

 Figure 12. Great Middle Cretaceous transgression of the oceans 



over the lands 77 



Figure 13. Diagram showing time and extent of the known 



floods that have inundated North America since the 



close of the Proterozoic era 79 



