XIII.] GEOGNOSY OF THE APPALACHIANS. 253 



lar quartz ; 2. Stockbridge limestone ; 3. Magnesian slate ; 

 4. Sparry limestone ; 5. Eoofing-slate, graptolitic ; 6. Sili- 

 cious conglomerate ; 7. Taconic slate j 8. Black slate. The 

 apparent order of superposition differs from this, and it was 

 conceived by Professor Emmons that during the accumulation 

 of these Taconic rocks, the Green Mountain gneiss, which 

 formed -the eastern border of the basin, was gradually elevated 

 so as to bring successively the older members above the ocean 

 from which the sediments were being deposited. From this it 

 resulted that the upper members of the system, such as the 

 black slates, were confined to a very narrow belt, and never 

 extended far eastward ; although he admits that denudation 

 may have removed large portions of these upper beds. At a 

 subsequent period, a series of parallel faults, with upthrows on 

 the eastern side, is supposed to have broken the strata, given 

 them an eastward dip, and caused the newer beds to pass suc- 

 cessively beneath the older ones, thus producing an apparently 

 inverted succession, and making their present seeming order of 

 superposition completely deceptive. In speaking of this sup- 

 posed arrangement of the members of his Taconic system, 

 Emmons alluded to them as " inverted strata " ; while by Mr. 

 Marcou, the strata were said to be " overturned on each side 

 of the crystalline and eruptive rocks which occupy the centre 

 of the chain, producing thus a fan-shaped structure," etc.* I 

 have elsewhere shown that this notion, though to some extent 

 countenanced by his vague and inaccurate use of terms, was 

 never entertained by Emmons, whose own view, as denned in 

 his Taconic System (p. 17),t is that just explained. 



* Comptes Rendus de 1'Academie, LIII. 804. 



f See my further discussion of the matter, American Journal of Science 

 (2), XXXII. 427 ; XXXIII. 135, 281. It is by an oversight that I have, in 

 the latter volume (page 136), represented Barrande as sharing the miscon- 

 ception of Marcou, although his language, without careful scrutiny, would 

 lead us to such a conclusion. In fact, in the Bull. Soc. Geol. de France 

 ( (2), XVIII. 261), in an elaborate study of the Taconic question, Barrande 

 heads a section thus : " Renversement conpu pour tout un systeme," and then 

 proceeds to show that the renversement or overturn is only apparent, by 

 explaining, in the languagfe of Emmons, the view already set forth above. 



