NATURE 



29; 



THIRSDAY, SEPTEMBER 8, 1910. 



ORE DEPOSITS. 

 (0 The Ore Deposits of South Alrica. By J. P. Juhn- 



s;on. Part ii., The Witwatersrand and Pilgrims' Rest 



(loldfields and Similar Occurrences. Pp. vi + 51. 



(London : Crosby Lockwood and Son, 1909.) Price 



5^. net. 

 (2) The Geology of Ore Deposits. By H. H. Thomas 



and D. A. MacAlister. Pp. xi + 416. (London: 



E. Arnold, 1909.) Price ys. 6d. net. 



(i) ' 1 'HE second part of Mr. Johnson's "Ore De- 

 J. posits of South Africa," of which the first 

 part was reviewed in Nature, June 3, igog, vol. Ixxx., 

 p. 395, deals with the goldfields of the Transvaal. 

 The book is intended for the use of prospectors and 

 >tudents, and consists of brief descriptions of each 

 mining field and of short discussions of the genesis 

 of the ores. It is illustrated with sections of the mines, 

 and outline maps of which the shading is not always 

 clearly explained. The author gives an excellent sum- 

 mary of the arguments for the placer and impregna- 

 tion theories of the origin of the Rand ores, and says 

 that "judging them on their own evidence the writer 

 would unhesitatingly class them as detrital ore de- 

 posits " (p. 17). He suspends judgment, however, 

 from the consideration that the gold at Pilgrims' Rest 

 is due to impregnation. The ores at Pilgrims' Rest 

 are quartz stringers in dolomite and altered dolomite ; 

 and they are doubtless of the same origin as those in 

 the dolomites of South Dakota, which are strikingly 

 different in all essential characters from the 

 banket of the Rand. Mr. Johnson's remark that 

 the analogy between the ores of Pilgrims' Rest 

 and of the Rand is the strongest argument in favour 

 of the impregnation theory for the banket is not 

 complimentary to the other arguments. The most 

 useful parts of the book are the chapters on the less- 

 known secondary goldfields of the Transvaal. 



Ij) Messrs. Thomas and MacAlister's "Geology of 

 Ore Deposits " agrees with Mr. Johnson's book in the 

 conciseness with which it summarises the structures of 

 various mining fields. It is, however, world-wide in 

 its range. It should prove of great service as a text- 

 book to students of economic geology who desire a 

 clear statement of current theories. As the authors, 

 in 416 small pages, state the principles of ore forma- 

 tion and explain them by reference to occurrences in 

 nearly every mining country, the work necessarily 

 suffers by extreme compression. There are no refer- 

 ences to authorities, and, owing to their absence, the 

 reader is sometimes left in doubt whether evidence 

 opposed to the authors' conclusions has been weighed 

 and rejected or has escaped their diligent search. 

 .\n omission that might have been avoided is an index 

 of localities. The same mining field may be referred 

 to in different chapters, and so many mining localities 

 are mentioned that a geographical index would have 

 added greatly to the usefulness of the book as a work 

 of preliminary reference. Some statistics of ore yields 

 would also have been an advantage as showing the 

 relative importance of the different processes of 

 NO. 2132, VOL. 84] 



mineral deposition ; the authors mention some insig- 

 nificant ore occurrences which are of no economic 

 importance, and some of which have not been worked, 

 and inferences drawn from them as to the origin of 

 the larger ore masses may be invalid. Owing to the 

 wide range of the book it is not surprising that it 

 contains small mistakes, both geological and geo- 

 graphical, in reference to foreign mining fields. 



The classification of ores adopted bv the authorities 

 is based solely on genetic grounds. They describe 

 first the ores due to the segregation of metals in 

 igneous rocks, a process to which the authors perhaps 

 attach undue importance, judged bv the economic 

 value of the ores thus produced. In succeeding 

 chapters they describe ores due to pneumatolysis, to 

 the action of heated solutions resulting from igneous 

 intrusions, to metasomatic replacement, to meta- 

 morphism, to precipitation, and to the deposition of 

 detritus. A special chapter describes the changes irt 

 ore deposits apart from those included under meta- 

 morphism. The authors show remarkably wide- 

 acquaintance with the literature of ore deposits and a 

 sound and cautious judgment. They accept the de- 

 trital origin of the gold in the Rand Banket, and 

 reject the view that nuggets are formed by deposition 

 from solution in the drifts wherein they are found. 

 The accounts of the British and especially of the 

 Cornish ores are the best in the book, many of the 

 references to the foreign fields being too brief to do 

 more than show the place assigned to the ores in the 

 authors' classification. 



One significant and interesting feature in this book 

 is the complete abandonment in a British text-book of 

 that morphological classification of ores which was 

 for so long dominant in this country that it has beert 

 described as "the British classification." 



J. W. G. 



OBSERVATIONAL METEOROLOGY. 

 Meteorology, Practical and .Applied. By Sir John 

 Moore. Second revised and enlarged edition. Pp. 

 xxyii + 492. (London : Rebman, Ltd., 1910.) Price 

 JOS. 6d. net. 



DL'RIN'G the last fifteen years much pro- 

 gress has been made in the study of 

 meteorology, as a comparison between the first 

 and second editions of Sir John Moore's treatise 

 amply demonstrates. Expansion in some direc- 

 tions necessitating curtailment in others has 

 changed and improved the work. .\s an example 

 of addition we may instance the account of the investi- 

 gation of the upper atmosphere with the information 

 acquired of the isothermal layer and the behaviour of 

 air currents. This inquiry, practically limited to the 

 interval between the appearance of the two editions, 

 has reacted, in various ways, traces of which will be 

 found in the book. It has given a strong impulse 

 to the \v;ork of designing accurate self-recording in- 

 struments, necessitating a considerable increase in the 

 chapters devoted to the methods of measurement and 

 registration of climatic factors. Through the increased 

 attention attracted to meteorology and the firmer 

 scientific foundation thus acquired, there has arisen the 



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