INTRODUCTION 



811 



Journal of Geology under the title "The Chester series in Illinois." 

 Aside from matter that is repeated in all of his later publications on 

 Chester formations — he never forgets to expose the mistakes of Ulrich — 

 this paper is notable because of a new classification of the Mississippian 

 system, differing from all preceding by the division of the Chester into 

 three groups and the system into but two series, the Chester series above 

 and the Iowa series below. The boundary between the two is drawn at 

 the base of the Aux Vases sandstone. Kegarding these innovations, it is 

 hardly necessary to say that I can not accept them. My objection to 

 drawing a major boundary between the Sainte Genevieve and the Aux 

 Vases has in the course of years only grown more firmly rooted; and I 

 see as many reasons as ever for an important line between the Warsaw 

 and the Keokuk. Then, as regards the asserted taxonomic equivalence 

 of the "Iowa series" and the "Chester series," even excluding the Sainte 

 Genevieve group, it seems to me that Weller has unduly emphasized the 

 Chester and greatly underestimated the importance of the Meramecian, 

 Osagian, and Kinderhookian epochs. About half of the Chester units 

 that he recognizes as distinct and full-pledged formations should be 

 merely lithologic members of broader units that might with propriety be 

 called formations. The sandstones in most or all of the Chester instances 

 are but clastic introductions of the succeeding limy stages. They are 

 useful datum planes in classifying a most variable series of deposits, and 

 so I am glad to distinguish them by the names assigned to them by Engel- 

 mann, Keyes, Butts, and Weller. But outside of Illinois, Indiana, and 

 western Kentucky, the Chester sandstones may be entirely wanting with- 

 out materially reducing the completeness of the sedimentary record. 



MATTERS IN CONTROVERSY WITH PROFESSOR WELLER 



The more important matters on which Weller held and still holds views 

 differing from mine were vigorously defended in the volume published 

 for me by the Kentucky Geological Survey in 1917. These disagreements 

 pertained (1) to the basal boundary of the Chester group, I having in- 

 cluded the whole of the Sainte Genevieve limestone in the Chester, 

 whereas Weller draws the line at the top of what I have, for purposes of 

 discussion, designated as the "Lower Ohara" or zone 1 of the Ohara 

 member of the Sainte Genevieve. 



(2) I correlated the sandstone to which I wrongly applied the name 

 Cypress in 1905 with the Aux Vases sandstone of the Mississippi Valley, 

 whereas Weller now adopts the name Bethel for this sandstone and corre- 

 lates it with his Yankeetown formation, which is typically developed in 

 Monroe and Eandolph counties, in western Illinois. The Aux Vases 



