April 5, 1906] 



NA TURE 



547 



Hall has been able to examine the rocks traversed by the 

 new shafts and drives. The field was extended, while 

 his paper was in preparation, by a further discovery on 

 the farm Ylaklaagte. In this case there is evidence 

 of the deposition of the cassiterite in good crystals, of the 

 size of coarse shot, throughout a granitoid rock, which 

 is of later age than the surrounding red granite. Minerals 

 containing fluorine, topaz being among them, are already 

 known in the Bushveld igneous series, and hence there is 

 reason to believe that the tin-ore may have been developed 

 nil Enkeldorn and Ylaklaagte in the manner recognised 

 in the "classical stanniferous localities." 



Mr. II. Kynaston appropriately describes (ibid., p. 61) 

 rocks allied to greisen, from a point much further north, in 

 the Olifants River Valley. He also adds to our knowledge 

 of the norites and schists associated with the Bushveld 

 granite, perhaps as marginal phenomena. Dr. Molengraaff, 

 whom we regard almost as a veteran in these years of 

 rapid exploration, and as the founder of much of our 

 knowledge of the Transvaal, further supports his view 

 (ibid., p. 63) that the Pretoria series may be correlated 

 with the jasper beds of Griqualand West. He now de- 

 scribes Mr. Leslie's discovery of crocidolite in the ferru- 

 ginous quartzites of the Pretoria series in the Lydenburg 

 district. These beds overlie the well known dolomite, 

 which thus may be paralleled with the Campbell Rand 

 dolomite of the south. Dr. Molengraaff s account of con- 

 tact-altered rocks in the Pretoria series should fit in with 

 Mr. Kynaston 's observations further north; and the con- 

 ferences of the Geological Society of South Africa will 

 doubtless show how much of the extensive alteration is 

 due to the granite and felsite series, and how much to 

 1 lie sheets of norite. The present tendency, however, 

 seems to be towards the linking of these two types of 

 intrusive rock in a continuous series. 



Mr. Thord-Gray (ibid., p. 66) describes in some detail 

 the occurrences of gold in the Pretoria series round 

 Pilgrim's Rest (Lydenburg gold-field), and concludes in 

 favour of the view that a mineral infiltration, carrying 

 both gold and copper, took place along certain zones of the 

 conformably bedded series. The horizontal " reefs " may 

 thus be described as altered quartzites. 



The correlation of the members of the Transvaal system 

 is again taken up by Prof. Schwarz, who attacks the 

 problem in the north of Cape Colony, in Prieska. He has, 

 quite independently, reached the same conclusions as Dr. 

 Molengraaff, and, with certain cautious reservations, passes 

 his comprehensive eye over similar beds in India and North 

 America also. The extraordinary uniformity of deposits 

 in South Africa across enormous areas certainly gives one 

 a new faith in lithological stratigraphy ; and it is on this 

 ground that Prof. Schwarz wishes to bring" together the 

 two series of ferruginous jaspers in the southern part of 

 the Transvaal, calling in a thrust-plane to his assistance. 

 The general feeling will be, both in our islands and in the 

 Transvaal, that detailed mapping will ultimately bring a 

 just correlation in its train. But detailed geological 

 mapping requires good topographic maps, and the limited 

 resources of the colony seem just now, from a legislator's 

 point of view, to have many prior claims upon them. 



Mr. F. P. Mennell shares with the equally energetic 

 Mr. A. J. C. Molyneux the task of elucidating the geo- 

 logical problems of Rhodesia, a region about as large as 

 France, Germany, Austria-Hungary, and Italy put 

 together. The gold problem is naturally the first thing to 

 be investigated, and Mr. Mennell (ibid., p. 82) seeks to 

 correlate the Rhodesian " banket," which he shows to be a 

 true conglomerate, with the gold-bearing series of the 

 Rand at Johannesburg. "So far," however, "it is only 

 at the Eldorado Mine, in the Lomagundi district, that gold 

 has been proved to exist in pavable quantities " in the 

 banket of Rhodesia. As Prof. J. \V. Gregory recently 

 informed us, other deposits or vein-stuffs may have become 

 known as banket, and it is certainly wise to restrict this 



iiii, of Transvaal origin, to the quartzose conglomerates, 

 wherever they occur. In Rhodesia, Mr. Mennell has to 

 deal with a metamorphosed series of sediments, including 

 these conglomerates, and penetrated by ancient and now 

 schistose basic rocks. The widely occurring granite is 

 later than the basic intrusions, and has produced consider- 

 able contact-alteration in the entire series. The gold, in 



accordance with the view now prevalent for the Rand de- 

 posits also, is regarded as a subsequent infiltration. 



Part ii. of vol. xxxii. of the Records of the Geological 

 Survey of India contains Mr. Hayden's " Preliminary Note 

 on the Geology of Tibet," already noticed in this Journal 

 (Nature, vol. lxxii., p. 285), and Dr. T. H. Holland's 

 paper on the occurrence of bauxite in India. The 

 latter author directs further attention to the aluminous 

 nature of the Indian laterites, and throws the whole field 

 of these rocks open to the prospector. He points out 

 (General Report of the Survey, ibid., p. 142) that the red 

 bauxites of Les Baux were first worked as iron-ores ; and 

 in his paper on bauxite the analyses of Indian samples 

 are all from rocks previously known as laterites. A very 

 interesting point is the high percentage of titanium dioxide 

 revealed, and Dr. Holland supports Dr. R. S. Bayer in 

 believing that some unfamiliar and possibly new substance 

 becomes precipitated with the titanium in these cases. Dr. 

 Holland regards bauxite as an intimate admixture of 

 gibbsite, Al 2 0,.3H..O, and diaspore, A1,0 3 .H.,0. 



Another Indian paper is by Mr. E. \Y. \Yetherell, on 

 the dyke rocks of Mysore (Mysore Geological Department 

 Memoirs, vol. ii.), in which a large number of specimens 

 are conscientiously described. The descriptions suffer, 

 however, from the fact that the species of triclinic felspar 

 are not determined. Nor are the misprints so few as the 

 " corrigenda " might lead one to suppose. The drawings 

 for the plates show exceptional care and delit :ai y. 



Mr. G. H. Girty, of the U.S. Geological Survey (Proc. 

 Washington Acad, of Sciences, vol. vii., June 20, 1905, 

 p. 11, has instituted a comparison between the Carbon- 

 iferous faunas of western America and those of Russia and 

 other areas. The ultimate result tends to the increase of 

 the Upper Carboniferous series in America at the expense 

 of beds now classified as Permian. The polyzoan 

 Archimedes, moreover, is shown to possess a far wider 

 range than would be gathered from a consideration of the 

 typical American deposits. 



Messrs. Stanton and Hatcher, assisted by Mr. Knowlton, 

 discuss the geology and palaeontology of the Judith River 

 beds, in northern and central Montana and the adjacent 

 parts of Canada (Bulletin 257, U.S. Geol. Survey, 1905). 

 The outcome of stratigraphical study, and the examination 

 of the vertebrate and plant remains, show that these beds 

 are no longer to be regarded as on the Laramie horizon, 

 but are Senonian at the highest, and reach down to the 

 Cenomanian. 



The same survey (Bulletin 262) issues contributions to 

 mineralogy, by several authors. The researches on which 

 these careful papers are based arose in connection with 

 the general work of the survey, and the results are here 

 conveniently brought together. Messrs. Hillebrand and 

 Ransome discuss the nature of carnotite (p. 18), which, 

 " instead of being the pure uranyl-potassium vanadate, is 

 to a large extent made up of barium and calcium com- 

 pounds." From this " mixture of minerals " the true 

 carnotite remains to be extracted and defined. Messrs. 

 Lindgren and Hillebrand (p. 48) incidentally direct attention 

 to the optical properties of chrysocolla, which, though 

 noticed by Jannetaz, have been very generally overlooked. 

 Mr. Schaller (p. 115) gives us a critical analysis of 

 dumortierite, deducing thence the formula 



8Al 2 3 .B„0 3 .H,0.6Si0 2 . 



The boron oxide was first indicated by R. B. Riggs in 

 [887. These are only a few of the matters that will attract 

 mineralogists to these 147 pages. 



The surface-features of the glaciated areas of North 

 America have provided a wide field for description and for 

 controversy. Mr. R. S. Tarr has sent us four papers, in 

 which various problems are set forth. That on moraines 

 of the Seneca and Cayuga lake valleys (Bull. Geol. 

 Soc. America, vol. xvi., p. 215) is mainly descriptive. 

 The drainage-features of central New York (ibid., p. 229) 

 involve questions of stream-capture, the lowering of water- 

 partings, and the formation of new slopes by detrital de- 

 posits, such as delight the glacial expert. A geographical 

 account of the gorges and waterfalls of central New York 

 (Bull. American Geographical Soc, April, 1905) is largely 

 concerned with the relations of pre-Glacial and post-Glacial 



NO. 1901, VOL. 73] 



