NA TURE 



[XOVEMBER II, 1909 



THE DIAMONDS OF SOUTH AFRICA. 

 Die diamantfiihrendcn Gesteine Siidafrikas, ihr 

 Abbaii und Hire Aufhereitung. By Dr.- Ing. Percy 

 A. Wagner. Pp. xviii + 207. (Berlin: Gebriider 

 Borntraeger, 1909.) Price 7 marks. 



AMONG the numerous works that have appeared 

 on the subject of South African diamonds, the 

 book before us is worthy of a very high place. The 

 author has examined the diamond-bearing rocks and 

 their relations during a visit to South Africa, and has 

 studied the materials brought home in the laboratories 

 of Prof. Rosenbusch in Heidelberg, and under Prof. 

 R. Beck at Freiberg, to the latter of whom the work 

 is dedicated. 



The record of previous literature at the beginning 

 is very full and complete, comprising the titles of 138 

 memoirs and books, besides general references to 

 periodical publications. The distribution and character 

 of the various "pipes" are clearly described, and the 

 series of comparative ground-plans drawn to scale on 

 p. 7 is very striking and instructive. The second 

 division of the book contains an admirable account of 

 the various minerals found in the pipes, of which 

 minerals no fewer than about thirty species are 

 described. In his chapter on the petrography of the 

 country, the author adopts the views of Carvill Lewis 

 and Bonney concerning the important part played by 

 the rock to which the first-named author gave the 

 name of " Kimberlite " ; but besides the form of the 

 rock first described from the Kimberley district, Dr. 

 Wagner indicates the existence of a variety much 

 richer in mica (biotite), which occurs in dykes in 

 Orangia and northern Cape Colony. These rocks 

 have been carefully studied by the author, who gives 

 chemical analyses of them and the results of investiga- 

 tions under the microscope, illustrated by two plates 

 containing photographs of rock-sections. 



Since the discovery of diamonds enclosed in masses 

 of eclogite (the " griquaite " of Beck) in the pipes of 

 South .Africa — a discovery announced in this country 

 by Sir William Crookes and Prof. Bonney in 1907 — 

 special interest attaches to the various fragmentary 

 rock-masses which occur so frequently in the "blue 

 and yellow grounds" of the South African mines. 

 The author devotes especial attention to the characters 

 of this diamond-bearing eclogite, and cites the case of 

 a similar rock having been found in the Bingera 

 diamond field of New South Wales, as related by Mr. 

 G. W. Card. It is interesting to notice that not only 

 diamond but crystalline plates of graphite have been 

 found by Harger and by Beck, enclosed in the eclogite 

 masses. Various other rock fragments and mineral 

 aggregates occurring with the eclogite masses are 

 described in detail. The evidence of the existence of 

 diamond enclosed in olivine, and of microscopic 

 diamonds distributed through kimberlite, is also dis- 

 cussed, and the bearing of all these and other facts on 

 the vexed question of the origin of the diamond is 

 considered. The whole of the observations bearing on 

 the subject appear to us to be stated very clearlv and 

 impartially. 



VV'e naturally look in this work for some account of 

 NO. 2089, VOL. 82] 



the new diamond-fields of German South-west Africa, 

 but at present the information upon the subject 

 appears to be somewhat meagre. According to the 

 only scientific account of the district which has as yet 

 appeared, the diamonds occur in an undisturbed 

 formation of Cretaceous Sandstone.. This sandstone, 

 according to Merensky, however, consists in great 

 parts of grains of chalcedony and agate, derived from 

 an amygdaloidal diabase, and it is this rock which is 

 regarded by him as the original source of the 

 diamonds. In 1908 this diamond-field had yielded a 

 great number of small diamonds (usually four or five 

 to the carat) of the aggregate weight of 39,762 carats 

 and of a value of 550,000/. 



The later chapters of the book deal with the methods 

 of mining the "blue ground," and the different kinds 

 of treatment to which it is subjected in order to 

 extract the diamonds. a\ number of photographs of 

 the various workings, and of the machinery employed, 

 adds to the interest of these chapters, the information 

 in which has been apparently obtained from trust- 

 worthy sources. The work closes with some interest- 

 ing statistics showing the weight and value of 

 diamonds yielded by each of the mining districts, and 

 the average value per carat in each case. From i8g8 

 to 1908 nearly thirty-one millions of carats were 

 obtained in South Africa. 



A LOST OPPORTUNITY. 

 The Stone Ages in North Britain and Ireland. By 

 the Rev. Frederick Smith. With an introduction by 

 Prof. Augustus H. Keane. Pp. xxiv-i-377; illus- 

 trated. (London : Blackie and Son, Ltd.) Price 6s. 

 net. 



THE problem of the Stone ages is one that is full 

 of complications. The greater part of it yet 

 remains unsolved, for the sum of our actual know- 

 ledge of the conditions of Palaeolithic man is as 

 nothing in comparison with our ignorance. By small 

 degrees advances are made. It is found, for example, 

 that in other continents the remains of analogous 

 culture stages bear that striking resemblance to those 

 of our own that is one of the most surprising features 

 of the study of prehistoric man in all periods. But 

 such additions to knowledge, interesting as they are, 

 help but little to enable us to picture the lives of the 

 men whom they concern. The advance must of 

 necessity be slow, for it is given to few to be able to 

 read in nature's writing the very incomplete record of 

 early man. While empiricism may make a lucky shot 

 now and then, it can be only to the trained and 

 reflective searcher tliat we must look for any effectual 

 progress. Of such trained and industrious men there 

 is no lack, and their accumulated experience, sifted 

 by a master, might even now be brought into line for 

 the less instructed public. Meanwhile, we have en- 

 thusiasts, like the Rev. Frederick Smith, who spend 

 years in gathering specimens and deducing theories 

 from them, and present us with ample volumes, like 

 the present one, well printed and fully illustrated, and 

 with this for the moment we must be content. 



Mr. Smith is an amateur in all senses of the word. 



