APPENDIX. 857 



ness of the stratified rocks. — 145, 146. Subdivisions of North America into independ- 

 ent regions of progress. 



XI. Archaean Time. —Pages 146, 147. The early Azoic part; its three earlier eras. 



— 147. Extent of the Archaean rocks. — 148. Its fourth era. — 148-150. Distribution in 

 North America. — 151. The two periods. — Kinds of rocks; prevalence of iron-ore. — 

 152. Graphite. — 152-154. Arrangement of the rocks. — 154. Their original condition. 

 — 155. Disturbances and foldings. — 156. Proof that there were long ages of quiet in 

 the course of Archaean Time. — Alterations or metamorphism of the rocks; examples. — 

 157. Life in the Archaean. — Evidences as to plants. — 158. Evidences as to animals 

 — 159. Huronian Period; the rocks so-called. — 160. Relations of the North American 

 Archaean areas to the present continent. — 161. Source of the material of later frag- 

 mental rocks. — Characteristics of the earliest life. 



XII. Paleozoic Time, Silurian Age. — Page 162. First of the Paleozoic Ages; 

 origin of the term Silurian; subdivision of the Silurian into two parts. —163. Names 

 of the three Periods in the American Lower Silurian, beginning with the earliest. — 

 164. Id. in the Upper Silurian. Primordial Period. — 166. The two Epochs of the 

 Period. — 166, 167. General distribution of the rocks in America. — 167. Kinds of 

 rocks. — 168. Markings in the rocks. — 169. General fact with regard to the life. — 

 Kinds of plants. — The Sub-kingdoms of animals represented. — The kinds of Radiates. 



— Id. of Mollusks. — 170. Id. of Articulates. — 173, 174. The earliest Mollusks. — 174. 

 The earliest Articulates. — 175. Graptolites. — 176. Footprints. — 179. Primordial rocks of 

 Great Britain. — 180, 181. North American Geography. — 181. Climate. —182. Ex- 

 termination of life ; Disturbances during the Primordial. 



XIII. Lower Silurian — Canadian Period. —Page 182. Epochs. — 183. Rocks. 

 — 185. Igneous rocks of the Lake Superior region. — 185, 186. Copper mines. — 186. 

 General fact respecting the life. — 187. The kinds representative of the several sub- 

 kingdoms of animal life, Protozoans. Radiates, Mollusks, Articulates; the most common 

 of Mollusks. — 188. Trilobites. — 192. European rocks. — 192,193. General character- 

 istics of the Period. — 193. Origin of the limestones. 



XIV. Lower Silubian. — Page 194. The third Period in the Silurian Age. — Its 

 Epochs. — General character of the Trenton rocks, and their distribution. — 194, 195. 

 Rocks of the Utica and Cincinnati epochs. — 197. Kinds of plants. — The prevailing 

 kinds of animal life. — 199. New Radiates. — The most abundant of Mollusks; the 

 kinds associated with these. — 200, 201. Kinds of Cephalopods, and the character of 

 their shells. — 202. The most common of Articulates. — 206. Rocks in Great Britain. — 

 208. Evidence as to the Geography of America. — 209. Climate. — Exterminations of 

 life. 



XV. Lower Silurian. — Page. 210. General facts respecting the Lower Silurian. — 

 The Eastern-border region in American geological history. — 210, 211. Diversity between 

 the Appalachian and Interior regions as to the kinds and thickness of rocks. — 211. 

 Evidence as to subsidences through the Lower Silurian over the Appalachian region. — 

 General quiet of the Lower Silurian era. 



Disturbances at the closk of the Lower Silurian. — Page 211. Region of 

 principal disturbance, and the evidence. — 212. Present position of the rocks. — 213. 

 Texture of the rocks ; fractures, faults. — 214. Width of disturbed region. — 216. Evi- 

 dence as to the time of the epoch of disturbance. — 216. Characteristics of the force en- 

 gaged. — 216, 217. Contrast in the condition of the region of the St. Lawrence Gulf. — 

 217. Cincinnati uplift ; events in Europe. 



XVI. Upper Silukian. — Page 218. General characteristics of the Upper Silurian. 



— Periods of the Upper Silurian. — Fourth Period of the Silurian, or first of the Upper 

 Silurian. — Epochs. — Kinds of rock, of the Medina and Clinton epochs. — 219. Rocks 

 of the Niagara epoch, and their distribution; thickness at Niagara Falls. — 222. Evi- 

 dence from structural peculiarities. — 223. Plants. — Common kinds of animal life. — 

 The Sub-kingdoms represented. — 230. Facts with regard to the Geography of the 

 Niagara Period. — 1st; 2d; 3d; 4th; 5th; 6th. — 230, 231. Conclusions as to geograph- 

 ical changes — 232. Condition, at the same time, of the region of the St. Lawrence Gulf. 

 Geographical condition of Europe and Arctic America. 



