August 12, 192 2 J 



NA TURE 



Mr. Orr's book can confidently be recommended for this 

 purpose. 



The book is simply written and can be read without any 

 extensive knowledge of English history : it is unbiassed 

 and, for its size, it gives as good an account as we have 

 vet seen of the course of events in British farming from 

 the earliest times to the present day. The illustrations 

 are excellent and well chosen from a wide range of 

 sources : they show, side by side, the older and the 

 newer types of implements or of animals, and afford 

 admirable demonstrations of the great changes that 

 have taken place since agriculture began to develop. 



In discussing the post-war period Mr. Orr ends on a 

 note of subdued optimism which we hope and believe 

 is justified : " The market for farm produce is weak. 

 Agriculture must share the bad fortune as well as the 

 good fortune of the country and even of the world. 

 In view of the magnitude of the war its evil effects will 

 probably be very great and very prolonged. But 

 however difficult times may be, there is promise for the 

 future in the better feeling that exists between landlords 

 and tenants, employers and employed, as compared 

 with that which prevailed a century ago. There has 

 been no poor-law payment of wages, and the difference 

 between the treatment of the labourer then and now is 

 an indication of the progress that has been made." 



E. J. Russell. 



Ore Deposits. 



Abriss der Lelire von den Erzlagerstatten : In Anlehnung 

 an die drilte Aufiage des Lehrbuches und unler 

 Beniilzung kinterlassener Aujzelchnungen. Von Prof. 

 Richard Beck. Bearbeitet durch Georg Berg. Pp. 

 xi + 40S. (Berlin : Gebriider Bomtraeger, 1922.) 

 16*. 8d. 



AS is stated by Dr. Berg in his introduction, this 

 Ix. work, an abstract of the study of ore deposits, 

 is an abbreviation of the large work in tw r o volumes by 

 Richard Beck. The original work was well known, 

 and three editions have been published since it was 

 originally issued in 1900. The general principle of 

 classification remains nearly the same as that in the 

 original work, and it must be admitted that, generally 

 speaking, the changes that have been made have not 

 made for a clearer understanding of this exceedingly 

 complex subject. 



As in the original, a clear cut is made between 

 epigenetic and syngenetic deposits ; the author defines 

 these phrases as follows : in the former he includes 

 deposits into which ore has been introduced only after 

 the formation of the immediately adjoining country 

 rock, while the latter term is restricted to magmatic 

 NO. 2754, VOL. I IO] 



segregation in which the ore is formed simultaneously 

 with the country rock. These basal definitions, 

 however, are by no means satisfactory. The author's 

 definition excludes from the syngenetic group sedi- 

 mentary deposits, such as beds of ironstone deposited 

 originally as bog ironstone, etc., and in fact Dr. Berg 

 has treated such deposits quite separately from his 

 syngenetic deposits and has placed them in his classifica- 

 tion after the epigenetic deposits. Dr. Beck, on the 

 other hand, looked upon such ores as syngenetic, and 

 there is no doubt that his view is the sounder and leads 

 to a clearer understanding of the entire subject. 



Again, Dr. Berg devotes a separate section to the 

 Gozzans or alteration products of existing ore deposits, 

 formed above permanent water level, which may 

 include both secondary enrichment and impoverish- 

 ment of the deposits in respect of their metallic con- 

 tents. He classifies these deposits as epigenetic on 

 the grounds that certain deposits are in themselves 

 not worth working except in the zone of secondary 

 enrichment ; perhaps, strictly speaking, there is 

 something to be said for this argument, but it certainly 

 does not make for a clear understanding of the subject. 

 If distinctions are to be drawn between the deposit 

 itself and its more or less altered outcrop, confusion 

 is bound to result. In fact, one of the great faults 

 of the work lies in the author's failure to appreciate 

 that in dealing with such phenomena as ore deposits, 

 where a natural system of classification is practically 

 impossible, broad lines must be followed ; even so, 

 there will be numerous border cases which every 

 student of the subject will treat on somewhat different 

 lines. One of the most striking points in the book, 

 which well illustrates what has just been said, is the 

 minute subdivision of mineral veins based upon 

 differences, and sometimes small differences, in their 

 mineral contents. In this Dr. Berg has followed 

 Dr. Beck, the need for simplification apparently not 

 having occurred to him. The whole of the treatment 

 of mineral veins may be described as somewhat 

 antiquated, seeing that over one-third of the work is 

 devoted to fissure veins. This diffuse treatment is 

 reminiscent of the days when the overwhelming 

 proportion of all metallic minerals (with the exception 

 of iron ores) was derived from fissure veins, as was 

 the case a century ago. To-day, on the other hand, 

 the output from veins is relatively unimportant, 

 and the author does not seem to have realised how 

 great the change has been in this respect. 



The author divides his subject into the following 

 main groups : 



I. Magmatic segregations. 

 II. Contact deposits. 

 III. Mineral veins. 



