VI CONTENTS. 



Chai'TKR V — Continucil. Page. 



Section II. — Origin of tlie rocks of the Iron-bearing member 24.'"i 



Tlie original rock, \>. 246. The ferruginous slates, p. 253. The ferruginous iherts, p. 

 254. The actinolitii- slates, p. 257. 



Section III.— The Aniniikie iron-bearing series 2t!(l 



'I'he rherty iron carbonates, p. 262. The ferruginous slates, ]>. 264. The ferrngiuons 

 cherts, p. 264. The aitinolitic slates, p. 266. General, p. 267. 



Section IV. — The iron ores - ' '-68 



Position of the ores in the Iron-bearing member, p. 268. Dikes in Iron-bearing member, 

 p. 271. Position of ore iu reference to the dikes, p. 274. Rock above the ore, p. 275. 

 Practical deductions to be applied iu jnospccting and niiniug, p. 276. Nature of the 

 rocks of the Iron-bearing member adjacent to the ore bodies, p. 279. The character 

 of the ore, p. 280. A particular occurrence of iron ore, p. 283. Chemistry of the 

 process of couceutratiou, jp. 283. Time at which concentration of the main ore bodies 

 occurred, ]>. 284. Process of concentration, p. 285. Exceptional localities, p. 290. 

 Probable extent in depth of cue bodies, p. 292. Emmons on ore deposits, p. 293. Ii'ou 

 ores in other parts of Lake Su))erior country, p. 293. Summary of more important 

 conclusions, p. 294. 



Chapter VI.— Thk Uppku Slate Member 296 



Section I.— Details 296 



Name and basis of separation, ]>. 296. Transition from Iron-bearing to Upper-slate 

 member, p. 297. Geographical distribution, p. 298 Topographical features, ji. 301. 

 General petrographical character, p. 302. Petrographiial characters of the four 

 types of rock, p. 304. Tabulation of petrographical observatious, p. 309. 



Section II. — < )rigiu of the upper slate rocks 332 



(1) Quartzose graywacke, (i. 333. (2) Muscovitic and biotitic graywacke, p. 336. 

 (3) Biotitic graywacke, p. 337. (4) Muscovitic biotite-slate, p. 338. (5) Nearly 

 crystalline muscovitic liiotite-schist, p. 339. (6) Crystalline muscovitic biotite- 

 schist, p. 340. Black mica-slates, p. 341. Source of material, p. 343. Summary, 

 p. 344. 



Chapter VII.— The Eruptives 346 



Structural relations, p. 346. General character of the rock, p. 348. Comparison of 

 Penokee greenstones with greenstones of the Southern Complex and Keweenaw 

 series, p. 349. Microscopical characters of the diab.a.ses, p. 3.50. Eruptives in the 

 Iron-bearing member, \>. 355. Summary, p. 358. 



Chapter VIII. — The Eastern Area 360 



Introduction - - 360 



Section I. — The Irou-bearing member 361 



Distribution, )). 361. Petrographical character, ji. 362. Mingled fragmental and 

 nonfragmeiital sedimentati(Mi, p. 362. Probability of ore deposits iu the Eastern 

 area, p. 365. Tabulalion of ])ctrogra]ihical observatious, p. 366. 



Section II. — Fragmental rocks sou 111 of the (irccnstone-conglomerates 368 



Geographi<al distribntiiui, |i. 368. Pcfrograpliical character, p. 369. Tabulation i>f 

 petrographical observatious, p. 371. 



Section 111. — The (ireeustone-conglomerates 374 



DistribnticMi, ji. 371. (ieneral characteristics, )). 371. Origin of the Cireeustoue-eon- 

 glomerates, ]). 377. Talnilatiou of iictrographical observatious, 381. 

 Section IV. — Fragmental aud ferruginous rocks uiirili and east of theGreeustone-cnugloui- 



erates -. 387 



