1S6 DK. THOMAS STBERY HUNT ON THE 



Toledo resting, according to Cortazar, directly upon the ancient gneissic rocks, but in the 

 Asturias, between these Cambrian strata and the ancient gneisses, there intervenes a 

 volume of not less than 3000 metres of strata, described as argillites and qtiartzites, w^ith 

 dolomites and limestones, sometimes saccharoidal and cipolin marbles, with beds of 

 specular iron-ore. As there is no apparent stratigraphical break between this younger 

 crystalline series and the strata holding the first fauna of Barrande, the name of Cambrian 

 is applied by Barrois to the whole."^ The student of American geology, however, recalls the 

 interposition between the Appalachian Cambrian and the ancient gneisses of a similar 

 great series, which suggests that in this region of Spain, as in parts of the Alps and in 

 Norway, we have a pre-Cambrian group that corresponds to the American Taconian. 



§ 210. It has been thought well, in concluding this essay on the present state of our 

 knowledge of the Taconian series in North America, thus to bring together, in a condensed 

 form, the principal facts with regard to certain rocks in the West India Islands, in South 

 America, in Hindostan, in Eussia, in the Alps, in Bavaria, in Norway and in Spain, which 

 tend to show that in all these various regions there exists a series analogous to the Taco- 

 nian, alike in mineral and lithological characters and in stratigraphical position. Should 

 further studies confirm this view, it will appear that the Taconian is a great and wide- 

 spread group of strata which cannot henceforth be overlooked in geognostical history. 



Summary of Contents. 



PART II. 



Chapter VIII. — The Taconic History Eevkued. — 136, 137. Different types of Cambrian in North America ; the Adiron- 

 dack, Mississippi and Cordillera regions. — 138. Billings on the Newfoundland Cambrian.— 139, 140. 

 Appalachian Cambrian, Upiser Taconic or First Gray vvacke.— 141. Relations of Cambrian and Ordovician 

 to Lower Taconic limestones.^142, 143. Mather's views of the Taconic re-stated. — 144. Emmons' view 

 re-stated ; the Red Sand-rock of Vermont. — 145. C. B. Adams and W. B. Rogers on the Red Sand-rock and 

 the Lower Taconic as (Upper) Silurian and Devonian.— 146. Ed. Hitchcock on the Devonian age of Lower 

 Taconic. — 147. Silurian outliers near Montreal and Hudson, New York. — 148. Wing and Billings on 

 Taconic in Vermont — 149, 150. Logan on Lower Taconic as altered Levis hmestone. — 151. J. B. Perry 

 on Taconic.^152. Marcou on Upper and Lower Taconic ; Silurian sandstones. — 153. Various views as 

 to the Vermont Sand-rock; the Lower Potsdam of Billings.— 154. Hall on the Hudson River group.— 155 

 Eord on Lower Potsdam in eastern New York. — 156. Its relation to the Loraine shales; dislocations of 

 strata.— 157. Logan and Billings on faults ; relations of Quebec and Potsdam groups.— 158. Dale and 

 Dwight on Cambrian and Ordovician in Duchess County. — 159. J.D. Dana on the Taconic question. — 160, 

 IGl. Emmons in 1842 on Taconic limestones, and Dana's comment thereon.— 162. Five different views as 

 to the age of the Lower Taconic limestones. — 163. The fifth and third noticed.— 164. Differences between 

 the views of Mather and Logan ; of Mather and H. D. Rogers.— 165, 166. Lower Taconic east of the Appa- 

 lachian valley ; absence of the Upper Taconic ; its distribution and distinctness.— 167. Dana's statements 

 criticised.— 168. The mistake of INIather and H. D. Rogers explained ; Eaton's view. — 169. Mather on 

 progressive metamorphism. — 170. The Lower and Upper Taconic compared with the Champlain division. 

 — 171. The Second Graywacke. — 172. The metamorphic hypothesis. — 173-175. Its application by Mather. — 

 176-178. Its application by Messrs. Rogers ; the two views compared ; geological map of New York. — 179. 

 Views of Emmons and Jackson ; Bigsby ; discovery of Huronian. — 180. H. D. Rogers in Pennsylvania in 

 1858 ; Hypozoic and Azoic systems.— 181, 182. W. B. Rogers in 1877 on the geology of Virginia.— 183. 

 Mather's metamorphic views discredited. — 184. J. D. Dana on metamorphism in south-eastern New York. 



''' Barrois, Recherches Sur les Terrains Anciens des Asturies et de la Galice ; Lille, 1882 ; 4to, pp. 623. 



