146 



INDEX 



Ultraviolet rays, 47-49, 51, 60 

 Umbgrove, J. H. F., 12, 13, 65, 



69, 71 

 Uniformitarianism, 7-10, 14, 16-19, 



42, 64 

 Uranium-lead method of dating, 



30-38 



Varved clays, 21, 25 

 Vertebrates, 125, 127 

 Vesuv, 9, 11, 14. 15 

 Virus, 127 

 Volcanism, 65, 119 



Weathering, 65, 94, 95, 97, 98, 112 



Weathering, chemical -, 95, 96 



Weathering, physical - (mechani- 

 cal -), 95, 96 



Weathering, reductive -, 98 



Whale, 125 



Wilson, A. E., 6, 52, 53. 58 



Winkler, K. C, 44 



Witwaterstand reef, 70, 99-101, 

 103, 105-107, 109 



Young, R. B., 79, 83 

 Zeuner. F. E., 21 



