TABLE OF CONTENTS. XIU 



on the subject, 405; JrnKX does the same, 495 ; both these writers show by 

 their writings that they have made no investigation of the facts, 495. Sweet, 

 in 1876, on a supposed unconfonnability of the Huronian and Laurentian at 

 Penokee Gap, 495, 496 ; Iuving on the same, 496 ; nature of such occurrences 

 not understood by the Wisconsin geologists, 496. Irving on the Huronian in 

 Wisconsin, 497 ; his ignorance of the necessary results of the intrusion of an 

 eruptive into a sedimentary one, 497 ; Iuving adopts some of Wadsworth's 

 lithological views, but omits to state the source from which they were derived, 

 497, 498. Hall, in 1866, refers the gneiss and granite of Redwood Kiver to 

 the Laurentian, and some quartzites in Minnesota to the Huronian, 498 ; 

 Hall's views opposed by Hayden and N. H. Winchell. The cupriferous 

 rocks on Lake Superior, within the limits of Minnesota, referred to the Potsdam, 

 in 1880, by N. H. Wikcuell, 498. 



THE FORTIETH PARALLEL SURVEY. 



What rocks are included in the " Archaean " by the Fortieth Parallel geologists, 499, 

 500. The Azoic or Archaan rocks of the Laramie Range, 500 ; Ziiikel'.s 

 distinctive characters of eruptive and sedimentary granites, 500, 501 ; defect of 

 his methods, 501 ; King's and A. Hague's statements at variance with each 

 other, 501. The Medicine Bow Range referred to the Huronian by A. Hague, 

 502 ; no proof given that it is older than Tertiary, 502 ; defects of observation, 

 502. The Uinta Range, 503. The Wahsatch R,auge, gradual change of views 

 in regard to its age, as volume succeeded volume, 503-507. Conflicting state- 

 ments of Zirkel and King, 507, 508. Criticism of King's statements, and of 

 his manner of observing, 508 ; similar criticisms by Geikie, 509, 510. Sum- 

 ming up of the results of the Fortieth Parallel Sui'vey, and indication of theii' 

 value, 510, 511. 



HAYDEX'S SURVEY. 



The rocks of the Chugwater, in 1868, called Laurentian, but no reasons given for this, 



511, 512 ; Havden, in 1869, states his theoretic views in regard to igneous and 

 metamorphic rocks, 512. Hayden calls the rocks on the north side of the Uinta 

 Range Silurian and Huronian, 512 ; the Fortieth Parallel Survey calls them 

 Carboniferous, Powell Devonian, Emmons Cambrian, and Marsh Silurian, 



512, 513. Endlich, in 1874, calls all the crystalline rocks in the region studied 

 by him, at the head of the Rio Grande and Rio Animas, Metamorphic Palaeozoic, 



513, Statement of Peale in regard to crystalline rocks, 513. Endlich divides 

 the Azoic rocks into three systems, 513, 514 ; he admits the insufficiency of his 

 observations, 514. Remarks by St. .T(ihn and Peale, 514. Summing up of the 

 condition of things in the Rocky Mountains, 514, 515. 



WHEELER'S SURVEY. 



No evidence offered in regard to the Azoic, 515. Stevenson in regard to age of rocks 

 called Archaean, in jmrts of New Mexico and Colorado, 515. 



