HISTORICAL GEOLOGY 93 



the Taconic system abound not only in Ordovician but 

 also in Cambrian fossils. Finally in 1888 Dana pre- 

 sented a Brief History of Taconic Ideas, and laid away 

 the system with these words (36, 27) : 



"It is almost fifty years since the Taconic system made its 

 abrupt entrance into geological science. Notwithstanding some 

 good points, it has been through its greater errors, long a hin- 

 drance to progress here and abroad . . . But, whether the evil 

 or the good has predominated, we may now hope, while heartily 

 honoring Professor Emmons for his earnest geological labors and 

 his discoveries, that Taconic ideas may be allowed to be and 

 remain part of the past. ' ' 



As an epitaph Dana placed over the remains of the 

 Taconic system the black-faced numerals 1841-1888. 

 That the remains of the system, however, and the term 

 Taconic are still alive and demanding a rehearing is 

 apparent to all interested stratigraphers. This is not 

 the place to set the matter right, and all that can be done 

 at the present time is to point out what are the things 

 that still keep alive Emmons 's system. 



In the typical area of the Taconic system, i. e., in Rens- 

 selaer County, Emmons in 1844-1846 produced the fossils 

 At ops trilineatus and Elliptocephala asaphoides. S. W. 

 Ford, as stated above, later produced from the same gen- 

 eral area many other fossils that he demonstrated to be 

 older than the Potsdam sandstone. To this time he gave 

 the name of Lower Potsdam, thus proving on paleon- 

 tological grounds that at least some part of the Taconic 

 system is older than the New York system, and therefore 

 older than the Hudson River group of Ordovician age. 



In 1888 Walcott presented his conclusions in regard to 

 the sequence of the strata in the typical Taconic area and 

 to the north and south of it. He collected Lower Cam- 

 brian fossils at more than one hundred localities 

 "within the typical Taconic area," and said that the 

 thickness of his "terrane No. 5" or "Cambrian (Geor- 

 gia)," now referable to the Lower Cambrian, is "14,000 

 feet or more." He demonstrated that the Lower Cam- 

 brian is infolded with the Lower and Middle Ordovician, 

 and confirmed Emmons 's statement that the former rests 

 upon his Primary or Pre-Cambrian masses. Elsewhere, 

 he writes: "To the west of the Taconic range the sec- 



