ulrich: major causes of oscillations 71 



those more inland and very ancient positive areas known as 

 the Cincinnati and Nashville domes, the Ozark and Adirondack 

 uplifts, and the Wisconsin peninsula. Of the many formations 

 that are found on their flanks and which failed to pass over 

 them much the greater number are confined to one or the other 

 side. The sequence of formations on either side therefore 

 differs greatly from that on the opposite side. 



Much space is devoted in my Revision of the Paleozoic Sys- 

 tems to a description of the inequalities in areal distribution of 

 the formations that were laid down on the flanks of these epi- 

 continental domes. With a few corrections and modifications, 

 in every case tending to emphasize rather than to weaken the 

 argument based on the observed phenomena, the pubUshed state- 

 ments concerning them in that work have been further sub- 

 stantiated by more recent investigations. Instead of over- 

 stating the number of oscillations in that paper we can now 

 prove many more instances than were known or even suspected 

 by me in 19 10. 



In New York State alone, the joint investigations carried 

 on in the Ordovician shales and limestones on the south and west 

 sides of the Adirondack mass by Doctor Ruedemann and my- 

 self, and on the Medina and Clinton formations with Mr. Hart- 

 nagle have increased the established cases of sea shifting im- 

 plying more or less decided differential vertical movements in 

 the adjacent land masses to more than twice the number con- 

 templated when I wrote the Revision. 



Similarly, the work of Mr. Charles Butts and myself, on the 

 Mississippian formations in Illinois, Kentucky, Tennessee, and 

 Alabama has developed oscillations of like character that were 

 scarcely suspected six years ago. 



Very notable additions to our knowledge of Cambrian and 

 Ozarkian oscillations also have been made in the course of my 

 work on the Paleozoic formations in Wisconsin. Before closing 

 permit me to give some details concerning at least one of many 

 similar new discoveries in this and adjoining States. 



Only a few years ago the stratigraphy of the Cambrian de- 

 posits in the upper Mississippi valley was practically unknown 



