MARYLAND GEOLOGICAL SURVEY 27 



vigorously in his lifetime. Still another classification of pre-Devonian 

 Paleozoic rocks is that of De Lapparent who recognized the Silurian for 

 the entire interval, with the three divisions ; Cambrian, Ordovician, and 

 Bohemian or Gothlandian. 



Another term which enters into this controversy is that of the Taconic 

 system. The Taconic question was the basis of a controversy in America 

 similar to that of the Silurian in Great Britain. In 1838 Emmons noted 

 that the Potsdam sandstone was the oldest sedimentary rock in the 

 vicinity of Potsdam, New York, as it here rested upon pre-Paleozoie 

 crystallines, an observation still recognized as correct. Overlying the 

 Potsdam sandstone, he found the Calciferous sandrock, the Chazy, Birds- 

 eye, and Trenton limestones, and the Utica and Hudson Kiver shales. 

 In western Massachusetts at the foot of the Hoosac Mountains he found 

 an entirely different series resting directly upon the gneiss. Emmons 

 believed this series to be older than the Potsdam and in 1841 he applied 

 to it the name Taconic system, after the Taconic range. The controversy 

 which arose over the reality of his system lasted over half a century, and 

 although Emmons defended his opinion until the day of his death, 

 stratigraphic geology had then not proceeded far enough to recognize the 

 real value of the Taconic rocks in classification. It is now known that 

 the greater portion of the Taconic is of Cambrian age. With slight 

 emendations the term Taconic could in all fairness have been recognized 

 for the Cambrian or for a portion of it just as Sedgwick's term Cambrian 

 should have been applied to the rocks now called Ordovician. 



During the quarter of a century or more following Lapworth's defini- 

 tion of the Ordovician system and the recognition in America of the 

 Cambrian, Ordovician, and Silurian, with the limits generally accepted 

 to-day, no controversial matters of especial importance arose in Early 

 Paleozoic stratigraphy. Most students of the subject believed that Early 

 Paleozoic sedimentation took place in quiet continental seas which were 

 often of considerable depth. It was thought that sedimentation endured 

 without interruption either through a single period or sometimes through 

 several periods, until finally there was land elevation and withdrawal of 



