82 



NA TURE 



[May 26, 1898 



and South Amboy in New Jersey, where they form the 

 local base of the Cretaceous group. The clays constitute 

 an important item in the mineral resources of the State. 

 The mollusca found in the Amboy Clays prove them to 

 be of estuarine origin. Compared with European strata 

 it seems probable that they may be regarded as Upper 

 Cretaceous. 



156 species of plants are described, and these include 

 8 ferns, 17 conifers, and 5 cycads, in addition to the many 

 dicotyledonous angiosperms, and a few doubtful forms. 

 No palms are recorded. 



Geology of the Denver Basin in Colorado.^ 



In this work the authors describe an area of about one 

 thousand square miles, in the centre of which stands the 

 city of Denver in Colorado. Topographically the area 

 itself forms a kind of basin, but geologically it has been 

 found that the rocks of the Cretaceous system, which 

 occur over a large part of the country, constitute a well- 

 defined syncline which is named the Denver Basin. 



The mountain range on the west comprises a crystalline 

 complex of pre-Cambrian rocks, flanked by highly inclined 

 rocks of the age of the Jura-Trias, and these are succeeded 

 with apparent though deceptive conformity by Cretaceous 

 deposits which assume a fairly horizontal position beneath 

 Denver, and are uptilted slightly on the east so as to 

 form the before-mentioned basin. 



It is held that considerable portions of the crystalline 

 nucleus of the Rocky Mountains constituted an archi- 

 pelago of large islands in the PaUeozoic seas. Within 

 the area now described no outcrops of Lower Palaeozoic 

 rocks are found, but there is good reason to believe that 

 they underlie the later sediments, and are concealed along 

 the Archaean borders by the overlapping Mesozoic and 

 later deposits. 



The movements that took place at various intervals 

 subsequently to the early Palaeozoic times are briefly 

 indicated. They are complex, and have variously affected 

 the character and distribution of the strata. The present 

 relations of the Jura-Trias and Cretaceous to the crystal- 

 line nucleus are not due to a simple vertical upward 

 movement of that core : the structure has rather been 

 produced by tangential compression, the effect of which 

 was to produce a structure somewhat analogous to a 

 vertical upthrust, but as a result of a horizontally rather 

 than of a vertically acting force. 



The strata referred to the Trias consist, curiously 

 enough, of brilliant red conglomerates, sandstones and 

 shales, with thin limestones and gypsums in the upper 

 part. They are known as the Wyoming formation, and 

 are overlaid by a series of freshwater marls — the Morrison 

 formation — grouped as Jurassic. This group is also 

 known as the Atlantosaurus clays, from its abundant 

 reptilian remains. 



The geology of these and of the succeeding Cretaceous, 

 Tertiary and Pleistocene formations, is exhaustively 

 treated, and there is a full account of the igneous rocks. 

 In the chapter on Economic Geology, coal, fire-clays 

 and other clays, building- stones, and artesian wells are 

 dealt with. The coal occurs in the Laramie formation of 

 the Cretaceous. A final chapter is devoted to Palaeon- 

 tology, including some account of the Cretaceous plants, 

 by F. H. Knowlton ; and of the Jurassic, Cretaceous, and 

 Tertiary vertebrates, by Prof. O. C. Marsh. 



The work is well illustrated with maps, sections and 

 pictorial plates. The " spherical sundering in basalt '' is 

 well shown in Plate xiv. Among other plates we have 

 restorations of the Jurassic Brontosaurus^ Stegosaurtcs, 

 Caniptosaurus, Laosaurtts, and Ceratosaurus ; of Cre- 

 taceous Birds and Dinosaurs ; of the Tertiary Mammals, 

 Brontops and Entelodon ; and of the Quaternary 

 Mastodon. 



1 ByS. F. Emmons, Whitman Cross, and G. H. Eldridge. (" Monographs 

 of the U.S. Geological Survey," vol. xxvii. Pp. xvii -i- 556.) 



NO. 1 49 1, VOL. 58] 



The Marquette Iron-bearing District of 

 Michigan.! 



i The Marquette district occupies an area extending 

 from Marquette on Lake Superior westwards to Michi- 

 gamme, a distance of rather less than forty miles, and 

 with a breadth of from one to over six miles. From the 

 western part of the main area two arms project for 

 several miles, one known as the Republic trough and one 

 as the Western trough. The district is the oldest 

 important iron-producing area of the Lake Superior 

 region. 



The rocks comprise three series, separated by un- 

 conformities. These are the Basement Complex or 

 Archaean, the Lower Marquette, and the Upper Marquette; 

 the two latter constituting the Algonkian of the district, 

 and perhaps equivalent to Huronian. The Marquette 

 series is mainly sedimentary, although among the strata 

 are included large masses of igneous rocks. The succes- 

 sion of the series is somewhat obscured by irregularities 

 of deposition, and by inter-Marquette erosion. After the 

 Upper Marquette series was deposited the district was 

 folded, faulted and fractured in a complex fashion, with 

 resultant profound metamorphism. 



The greater iron-ore deposits occur in the Negaunee 

 formation, which is from looo to 1500 feet thick, and 

 occurs in the Lower Marquette series. Petrographically 

 the formation comprises sideritic slate, ferruginous slate, 

 ferruginous chert, jaspilite, and iron-ore. The ferruginous 

 chert and jaspilite are frequently brecciated. The iron- 

 ores resulted from the concentration of the iron-oxides 

 through the agency of downward percolating waters. 

 These concentration-bodies usually occur upon impervious 

 basements in pitching troughs. 



The various features connected with this iron-producing 

 region are all worked out in great detail, and the 

 memoir is beautifully illustrated with coloured plates 

 of banded and brecciated rocks, and various pictorial 

 views and sections. H. B. W. 



ANTHROPOLOGY IN MADRAS. 

 "\1 7"HEN recently on furlough in England, I was greatly 

 * '^ interested in hunting up the facilities for the study 

 of anthropology in London, and in the scheme for the 

 establishment of a bureau of ethnology for the British 

 Empire. And it has been suggested to me that it may 

 interest those concerned in the development of anthro- 

 pological research to know what is being done, in a mild 

 way, in a remote possession of the Empire, the Madras 

 Presidency, viz. the southern portion of the Indian 

 peninsula. I add this geographical explanation, inas- 

 much as a friendly critic, in a recent review of my work, 

 got hopelessly mixed between Madras and Bengal, re- 

 minding me of the story of the Viceroy-elect, who was 

 overheard murmuring to himself, " Bombay in the west, 

 Calcutta in the east, Madras in the south." Wide as is 

 the area, and numerous as are the tribes, castes, and 

 races included within my limited beat of 150,000 square 

 miles, I have set myself the task, which must perforce 

 occupy many years, of carrying out a detailed anthro- 

 pological survey. This survey was, with the approval of 

 the Madras Government, inaugurated in 1894. In that 

 year, equipped with a set of anthropometric instruments 

 obtained on loan from the Asiatic Society of Bengal, I 

 commenced an investigation of the hill-tribes of the 

 Nilgiris, the Todas, Kotas, and Badagas, bringing down 

 on myself the unofficial criticism that "anthropological 

 research at high altitudes is eminently indicated when 

 the thermometer registers 100° in Madras." From this 

 modest beginning have resulted : (i) investigation of the 



1 By C. R. Van Hise and W. S. Bayley, including a chapter on the 

 Republic Trough, by H. Lloyd Smith. ("Monographs of the U.S. Geo- 

 logical Survey," vol. xxviii. Pp. xxvii + 608 ; 35 plates, and 27 other 

 illustrations, together with large lolio atlas of maps.) 



