TACONIC SYSTEM. 435 



series. The principal view held in this volume, which has now been changed, was that 

 the gray sandrock (or Oneida conglomerate) capped the Champlain group of lower Silurian 

 strata. That formation, the red sandrock of Snake Mountain, is now regarded by Prof. 

 Emmons as of the age of the calciferous sandrock underlaid by Taconic slates. 



In reply to objections that had been urged against the Taconic system, Prof. Emmons 

 continued his examination of the Taconic rocks, and in 1844 published a large quarto 

 pamphlet entitled The Taconic System. This volume develops the nature of the disturb- 

 ances, and describes the extent of the system much more fully and carefully than had 

 been done before. The objections of other geologists to the system are stated and answer- 

 ed, and the volume has a controversial air. 



But American geologists were generally arrayed against the Taconic system until 1860. 

 During this interval the anti-Taconic view was presented by Professors James Hall, C. B. 

 Adams, W. B. Rogers, and Sir Win. E. Logan. All the geologists who investigated the 

 Taconic rocks north of Tennessee were opposed to Prof. Emmons' views. No elaborate 

 works, but simply occasional articles in scientific journals, or abstracts of discussions in 

 Scientific Societies, were published by the opponents. In 1855 Prof. Emmons published 

 in his American Geology an elaborate defence of the Taconic system. Here he first ranks 

 the red sandrock series as lower Silurian, and divides the Taconic rock into upper and 

 lower. Subsequently similar defences and further descriptions have been published by him 

 in his Reports upon the Geology of North Carolina, and his Manual of Geology. 



The later anti-Taconic views generally adopt the opinions of the Professors Rogers in 

 regard to the synchronism of the lower Silurian and Taconic rocks. They make great 

 use of the doctrines of metamorphism, and apply its principles not merely to the Taconic 

 rocks, but to the crystalline rocks of all New England, supposing that none of them are 

 older than Silurian, and very few are as recent as the coal formation. Emmons seems to 

 discard the doctrines of metamorphism mostly, as if to grant them would be to give up 

 the Taconic system. Perhaps the anti-Taconic advocates have been carrying their theories 

 too far, and may yet be compelled to yield much. 



In consequence of the varying limits of the Cambrian and Silurian rocks of Europe, it 

 was difficult to compare the European and American rocks satisfactorily. Hence the first 

 statement was that the Taconic rocks underlie the Potsdam sandstone. We understand 

 Prof. Emmons more recently to claim that the words Taconic and Cambrian (as used by the 

 English Government Surveyors) are synonymous. If the Georgia slates are Primordial 

 then the upper part of the Taconic system must be Silurian according to the definition. 

 Perhaps Prof. Emmons will not hesitate to grant this. 



The latest aspect of the controversy rests upon the age of the red sandrock and Georgia 

 slates. These were both regarded as Middle Silurian by Prof. Hall and others. The 

 descriptions of the Oleni (Barrande) from the Georgia slates called out M. Barrande's views, 

 who unequivocally pronounced the rocks containing such fossils to be equivalent to those 

 containing the primordial zone of life in Bohemia, that is, to the Potsdam sandstone 

 of America. This does not agree with Emmons' views, for he distinctly places the Georgia 

 slates (Taconic slates) unconfonnably below the Potsdam sandstone. Yet M. Barrande; 

 supposes that his views will support the Taconic system. 



Immediately following M. Barrande's letters, Sir Wm. E. Logan published a letter to 



