2:;8 



NA rURE 



[^JULY 14, 1904 



some intrusive rocks which present in many cases a 

 schistose character. The Soudan formation, the oldest 

 sedimentary group in the district, is bent into prominent 

 anticlines, but is otherwise intricately contorted and infolded 

 with the greenstones; it comprises conglomerates with 

 fragments of the older greenstones, and an outlying group 

 of siliceous rocks, largely white cherts, with red jasper and 

 carbonate-bearing chert, griinerite-magnetite-schist, blue 

 hematite, magnetite, and small quantities of pyrite. The 

 cherty rocks are banded, and the hematite occurs in certain 

 places in masses of variable size, which constitute the ore 

 deposits. These iron-bearing rocks are considered to be 

 of sedimentary origin. The source of the iron was, in the 

 first instance, the Ely greenstone. From this it was removed 

 through the action of water and collected to form part of 

 the sedimentary marine deposits of the Soudan formation. 

 After the folding of the rocks this disseminated iron was 

 carried by downward-percolating waters into places favour- 

 able for its accumulation. The methods of mining are de- 

 scribed. There are descriptions also of the later intrusive 

 rocks, of the Huronian and Keweenawan series, of the 

 drifts, the Glacial lakes, and other topographic features. 



Monograph No. 46, on " The Menominee Iron-bearing 

 District of Michigan," by Mr. W. S. Bayley, is the sixth 

 and last of a series of reports on the iron-bearing districts 

 of the Lake Superior region. The area now described is 

 a very important one, as it has yielded since 1877 nearly 

 thirty millions of tons of iron-ore of Bessemer grade. The 

 rocks comprise Archsan schists and granites, which appear 

 on the borders of the district ; in the central portions the 

 iron-bearing Algonkian rocks, with basal conglomerate, 

 occupy a trough of highly folded rocks, distinguished as 

 the Lower and Upper Menominee series, there being a 

 marked unconformity between them. These divisions corre- 

 spond to the Lower and Upper Marquette series, and to 

 the Lower and Upper Huronian of other areas. .'\bove 

 these folded rocks lie horizontal Palaeozoic beds, com- 

 prising the Lake Superior sandstone and an Ordovician 

 limestone. The Lower Menominee series comprises 

 quartzite and dolomite, the latter affording a key to the 

 folding. The gap between Lower and Upper Menominee 

 series is marked by conglomerate at the base of the Upper 

 series, which contains pebbles of jaspilite (iron-bearing), 

 and these are taken to represent the Negaunee formation. 

 The Upper Menominee series comprises also slates, 

 quartzites, and jaspilites, these last-named being banded 

 rocks composed of alternating layers of red jasper and ore- 

 deposits. It is noted that the larger ore-deposits all rest 

 upon relatively impervious foundations, which are in such 

 positions as to constitute pitching troughs. The processes 

 of concentration were the same as those worked out in other 

 districts by Van Hise, being due to descending waters flow- 

 ing in definite channels. The concentration was commenced 

 after the folding of the rocks, and completed before the 

 beginning of the Upper Cambrian. The subject is treated 

 very fully from all points of view, structural and physio- 

 graphic as well as economic, and it is profusely illustrated 

 with maps, sections of the strata, microscopic' sections of 

 rocks, and pictorial views. There are also two plates of 

 possible organic markings from the iron-bearing rocks of 

 Chapin Mine : these were thought by Mr. W. S. Gresley 

 to represent impressions of plants, track-marks, &c. 



III. Professional Papers. 

 The United States Geological Survey has issued a series 

 of " Professional Papers," of which we'have received several 

 examples. No. 11 is on "The Clays of the United States 

 East of the Mississippi River," by Mr. Heinrich Ries. It 

 is interesting to note that while 'kaolins occur in several 

 States, the local output at present is insufficient to meet the 

 demand. No. 12, by Mr. F. L. Ransome, deals with the 

 "Geology of the Globe Copper District, Arizona." 

 No. 13 is on " Drainage Modifications in South- 

 eastern Ohio and Adjacent Parts of West Virginia and 

 Kentucky," by Mr. W. G. Tight. The subject is one which 

 attracts a considerable amount of interest, so far as it 

 illustrates the history of rivers and the relation of the old 

 to the present river systems. The author concludes that 

 the high-level valleys of the region represent a connected 

 NO. I 8 II , VOL. 70] 



system of an old drainage cycle which antedates the first 

 advance of the ice of the Glacial period ; that the deposition, 

 of the silts on the old valley floors and the deflection of 

 the streams producing the present drainage system were 

 due to the action of the advancing ice-sheet of the first 

 Glacial epoch ; that the extensive erosion of the present 

 river valleys to depths below the present drainage lines was 

 accomplished during an inter-Glacial interval of great 

 duration ; and that these inter-Glacial valleys were partially 

 filled with debris by the flood waters of the last Glacial 

 epoch, the post-Glacial erosion being represented by the 

 channels cut in the floor of these deposits since the rivers 

 have acquired their present. volume. Paper No. 14, by Mr. 

 Henry S. Washington, comprises a laborious but most useful 

 work, entitled " Chemical Analyses of Igneous Rocks Pub- 

 lished from 1884 to 1900, with a Critical Discussion of the 

 Character and Use of Analyses." The analyses follow on. 

 from the last date of publication of Roth's " Tabellen," and 

 include a few analyses of 1883 omitted from that work. 

 The author insists on the importance of careful and precise 

 work, lamenting that rock analyses are too often entrusted 

 to inexperienced students. The work will be of the greatest 

 value to petrologists. Paper No. 15 is on " The Mineral 

 Resources of the Mount Wrangell District, Alaska," by 

 Messrs. W. C. Mendenhall and F. R. Shrader. It deals 

 with the occurrence of ores of copper, gold, silver, platinum, 

 tin, mercury, osmiridium and iron, and also with a few 

 indications of coal or lignite. 



No. 16 is on " The Carboniferous Formations and Faunas 

 of Colorado," by .Mr. G. H. Girty. This work is based on 

 the extensive collections of fossils of the Geological Survey 

 and the National Museum, and its purpose is to ascertain, 

 by means of the invertebrata, their grouping into local and 

 formational faunas. It brings out the close relation which 

 existed in Carboniferous time between the Colorado seas 

 and those of the Mississippi valley. The Leadville, Mill- 

 sap, and Ouray limestones which form the base of the 

 Carboniferous, and which include a part of the Mississippian 

 fauna, include also in their lower portion a distinctive 

 Upper Devonian fauna. The Lower Carboniferous was fol- 

 lowed by an epoch of elevation and erosion, and none but 

 the early portion of the Mississipian time is represented in 

 the Colorado sediments. This lower group comprises (i^ 

 the Weber formation, of dark carbonaceous shales and thin 

 limestones, with fossils of Coal-measure type, and (2) the 

 Maroon formation, a great series of conglomeratic beds and 

 grits, surmounted by red sandstones. The same difliculties 

 that have been met with in Britain are encoimtered in 

 Colorado, and the author discusses at some length the 

 question whether certain red beds are Carboniferous, Per- 

 mian, or Triassic. The Wyoming " Red Beds series " 

 appears to succeed the Maroon formation in places without 

 a break, but the author regards it as really Triassic. The 

 numerous descriptions of fossils are accompanied by ten 

 plates. 



No. 17, by Mr. N. H. Darton, is a " Preliminary Report 

 on the Geology and Water Resources of Nebraska West of 

 the 103rd Meridian." The geology and topographic features 

 are described, and some remarkable monuments of erosion 

 known as the Chimney rock,, the Smokestack rock, and the 

 Twin-sisters are represented on photographic plates. There 

 is also a figure of the Titanotheriinn, which is found in the 

 basal portion of the Tertiary strata. 



In No. 18, Mr. J. P. Iddings contributes an essay on 

 " Chemical Composition of Igneous Rocks Expressed by 

 Means of Diagrams with Reference to Rock Classification 

 on a Quantitative Chemico-mineralogical Basis." In intro- 

 ducing this work Mr. Whitman Cross remarks, "As a 

 successful attempt at the elucidation of a comple.x problem 

 the paper is of importance to all students of igneous rocks." 



In No. 19, " Contributions to the Geology of Washing- 

 ton," by Mr. G. O. Smith and Mr. Bailey Willis, the 

 authors deal chiefly with the origin of the physical features. 

 No. 20, "A Reconnaissance in Northern ."Maska," by Mr. 

 F. C. Shrader, with notes by Mr. W. J. Peters, contains 

 much interesting information about tracts hitherto unex- 

 plored. Among the rocks described are Silurian, Devonian, 

 Carboniferous (?), Jura-Cretaceous, Cretaceous, and Ter- 

 tiary, as well as Drift deposits. The mineral resources, 

 climate, population, and other subjects are dealt with. 



