XIII.] GEOGNOSY OF THE APPALACHIANS. 277 



In what precedes I have endeavored to discuss briefly and 

 impartially some of the points in the history of the older rocks, 

 and of the views which during the past thirty years have been 

 entertained as to their age and geological relations, both in 

 America and in Europe. I have said some things which will 

 provoke criticism, and at the same time, I trust, lead to further 

 study of these rocks, a correct knowledge of which lies at the 

 basis of geological science. 



I cannot, however, conclude this part of my subject without 

 referring to the views put forth in 1869 by Professor Hermann 

 Credner, of Leipzig, in an essay on the Eozoic or pre-Silurian 

 formations of North America.* With Macfarlane, he refers to 

 the Huronian the gneissic series of the Green Mountains, but 

 includes with it, as part of the Huronian system, the so-called 

 Lower laconic rocks of Vermont, "with remains of annelids and 

 crinoids." Credner thus falls into the very error against which 

 Emmons warned American geologists, namely, the confounding 

 in one system the ancient crystalline schists with the newer 

 fossiliferous sediments. Resting unconformably on these, he 

 places, first, the Upper Taconic, corresponding, according to 

 him, to a part of the Quebec group ; and, second, the Potsdam 

 sandstone. In this he has copied, for the most part, Marcou, 

 who, however, groups the whole of these various divisions in 

 the Taconic system ; while Credner, rejecting the name, unites 

 a portion of the Taconic of Emmons with the Huronian system, 

 and refers the other portion, together with the Potsdam, to the 

 Silurian. These same views are set forth in a more recent 

 paper, by the same author, on the Alleghany system, which is 

 accompanied with sections and a geologically colored map.t 

 In this, not content with including in the Huronian both the 

 fossiliferous strata of the Levis formation and the crystalline 

 schists of the Green Mountains, he refers the gneisses and mica- 

 schists of the White Mountains to the same system ; while the 

 broad area of similar rocks from their base to the sea at Port- 



* Die Gliederung der Eozoischen Formationsgruppe, u. s. w., p. 53. Halle, 

 1869. 

 t Petennann's Geographische Mittheilungen. 2 Heft, 1871. 



