49S 



NA TURE 



[September 23, 1897 



amphibole. Nepheline- and augite-syenite, nepheline- 

 basall, and tufifs and breccias also occur. The acid and 

 intermediate rocks are rich in alkalies, and the latter erup- 

 tions were of strongly-contrasted acid and basic magmas, 

 conforming to the complementary types of Brogger. In 

 the mining portion of the memoir Mr. Penrose shows 

 that gold occurs deep down as a telluride which has been 

 ■decomposed near the surface to form native gold. The 

 ore deposits occur in fissures, blending into the country 

 rock, and generally associated very definitely with dykes, 

 because fissures have followed pre-existing dykes. De- 

 tailed descriptions of the country, with maps and sections, 

 follow, 



Mr. Eldridge's geological reconnaissance across Idaho 

 jfives a brief description of Archaean and Algonkian 

 rocks, which are overlain by Palaeozoic rocks whose 

 exact age is unknown, but apparently ranging from 

 Cambrian upwards, and including sub-Carboniferous 

 rocks. Cainozoic rocks follow, and igneous rocks of all 

 ages from Archaean to Tertiary are present. Several 

 mining districts, yielding gold and silver, are described, 

 and a little coal occurs in the Tertiary rocks. 



The Mercur mining district in Utah, described by Mr. 

 Spurr, with an introduction by Mr. S. F. Emmons, yields 

 toth gold and silver, the latter chiefly at the contact of 

 limestone with porphyry, where both rocks are altered 

 and decomposed, the former where the Eagle Hill 

 porphyry has produced a silicification of the limestone 

 with which it is in contact. The ores are associated 

 with sulphides, or else have become oxidized near the 

 surface, and the gold probably occurred originally as a 

 telluride. 



The economic volume closes with two papers, one on 

 the public lands and their water supply, by Mr. F. H. 

 Newell, and the other on the water resources of the great 

 plains, by Mr. R. Hay. The first paper indicates the 

 rate of progress in disposal of public lands, their general 

 agricultural character, and chief sources of water supply 

 from streams, wells, and reservoirs. The second shows 

 that, although the deep supply of water is limited, quite 

 sufficient for probable requirements may be obtamed 

 from the Tertiary grit, which is met with at depths 

 ranging from loo to over 300 feet. 



The two parts of vol. iii. of the Sixteenth Annual 

 Report are entirely devoted to mineral statistics and 

 papers germane to the mining industries. These statistics, 

 previously published as ordinary octavo, are now issued 

 in royal octavo, and form a part of the Annual Report. 

 The production of minerals is represented not only by 

 tables, but by curves and diagrams, so that their mean- 

 ing can be rapidly grasped, and with them are published 

 not only accounts of the various mining industries of the 

 United States, but notices showing the history and 

 present phase of the same industries all over the world. 

 Mode of occurrence of the various classes of ores, 

 methods of winning them, details of quarrying and 

 mining operations, and prices of products are all treated 

 in detail. Improved methods, whether adopted at home 

 -or abroad, are described in full, and every effort is 

 made to bring all the industries abreast, or to keep them 

 ahead, of what is done elsewhere. Many of the papers 

 are compact summaries of particular classes of deposits, 

 which will be extremely useful for those who require 

 to become rapidly acquainted with particular products 

 and industries. As examples of this, the articles on 

 bauxite and fertilisers may be noticed. The article on 

 iron contains a very useful set of maps, showing the 

 localities of iron ore deposits throughout the world. 

 Many of the other articles contain series of analyses, 

 and bibliographies are annexed to some of the papers. 



The scientific volume (Part i.) of the Sixteenth Annual 

 Report opens with a short and, to some extent, popular 

 paper on the dinosaurs of North America, by Prof. O. C. 

 Marsh, illustrated by eighty-five plates, indicating the 



NO. 1456, VOL. 56] 



principal structural characters of these reptiles, and giving 

 restorations where they are warranted by the number of 

 bones preserved. The plates were prepared for a series 

 of monographs now in preparation, and they are here 

 pubHshed in advance. Questions of classification are 

 relegated to a subordinate position, and the author con- 

 fines himself almost entirely to a short account of the 

 principal bones found, laying stress on the points which 

 justify the restorations adopted. A useful table showing 

 the horizons of vertebrate fossils in America is given, and 

 in this the beds are classified according to their dominant 

 vertebrate fossils, which, in the Mesozoic rocks, are 

 chiefly reptiles. It is shown that the so-called "bird 

 tracks " of Connecticut River are due to dinosaurian 

 reptiles, and not to birds. 



On comparing European with American Sauropoda, 

 Prof. Marsh notes the absence of the gigantic Atlanto- 

 saurida; and the Diplodocidtt from Europe, while the 

 Cardiodontidffi are abundant there. Restorations of 

 four European forms — Compsognathus, Scelidosaurus, 

 Hypsilophodon, and Iguanodon—?iV& published, and, in 

 conclusion, the affinities and classification of the dino- 

 saurs are discussed. 



Prof. H. F. Reid contributes a short memoir on Glacier 

 Bay and its glaciers, like those named after Muir, Rendu, 

 and Gushing, illustrated by an admirable series of photo- 

 graphs and profiles of the ends of the ice streams. After 

 dealing with the "hard" geology, the stratified gravels 

 are considered ; these rest on blue clay formed of stream 

 and moraine mud, covered with the tree stumps of a 

 forest which appears to have been living within a few 

 centuries until destroyed by floods and gravel. Certain 

 smooth holes in the ice are thought to be the result of 

 the closing of crevasses containing water by the ice- 

 movement. An eskerof sand and gravel, projecting one 

 hundred yards from the moraine of Dent Glacier, has a 

 winding course, and appears to have been produced by a 

 stream flowing in a channel through the ice. 



Part i. of the Sixteenth Annual Report closes with 

 three very important papers by Nelson Dale, Van Hise, 

 and Hoskins, dealing with a group of cognate subjects. 

 Mr. Dale gives a series of examples of various structural 

 phenomena which are well illustrated in the Green 

 Mountain region and in eastern New York. Different 

 types of folds, false-bedding, single, double and triple 

 cleavage, and evidences of stretching and brecciation. 

 This short paper is illustrated by drawings and photo- 

 graphs of sections and specimens, many of which are 

 referred to by Van Hise in the communication which 

 follows. 



Mr. Van Hise, in his "Principles of North American 

 pre-Cambrian Geology," gives, first of all, a set of prin- 

 ciples to guide field-work in these rocks, weaving to- 

 gether the results of his own rich experience with the 

 work of other observers, such as Heim, Lapworth, Rogers, 

 Gilbert, Dana, Geikie, Harker, and a host of others. 

 This is followed by an apphcation of the principles to 

 the different areas where pre-Cambrian rocks may be 

 studied in America. 



At a greater depth than 10,000 to 12,000 metres 

 cavities could not exist, even in the strongest rocks, and 

 all fissures and cracks would be closed and welded by 

 flowage of the rock material under the stress existing 

 there. Near the surface deformation of rocks by fracture 

 would be possible, and between the two zones there 

 would exist an area of combined fracture and flowage, 

 the strong rocks yielding by the former, and the weaker 

 by the latter process. Folds are simple or composite 

 if in two dimensions, complex if in three ; and it is 

 pointed out that the true succession can only be made 

 out in a complex district by unravelling the cross sets of 

 folds, or, what is the same thing, ascertaining the " pitch •' 

 of the axes of the minor folds. The structures hitherto 

 considered under the name of cleavage are separated 



