206 



NA TURE 



I August i 2, 1922 



IV. Epigenetic ore bodies. 

 V. Sulphuretted ore deposits mainly of epigenetic 



origin. 

 VI. Ores formed by sedimentation. 

 VII. Gozzans. 

 VIII. Secondary (clastic) deposits. 



Many of these groups are by no means satisfactory, 

 inasmuch as the deposits included in them do not 

 properly correspond to the titles given. Thus the 

 author quotes as examples of magmatic segregation 

 the magnetites in gneiss of the Lofoten Islands and the 

 Xiruna ore. although he admits that the latter ore 

 deposit is definitely younger than the adjoining eruptive 

 rocks and accordingly not syngenetic with these. 

 Similarly he includes among contact deposits, by which 

 he understands those formed under the influence of 

 contact metamorphism at or near the boundaries of 

 the eruptive and the stratified rock masses, a number 

 of deposits as to which he is bound to admit that he 

 cannot ascribe their origin to any particular eruptive 

 rock. He describes those as krypto-contact deposits, 

 but obviously such a description is far from satisfactory. 

 Among his epigenetic ore bodies he includes such 

 deposits as those of Bingham and Bisbee, where the 

 protore is undoubtedly syngenetic, gash veins and 

 similar deposits in pre-existing cavities, true meta- 

 somatic deposits like the red haematites of Cumberland, 

 and certain residual deposits, while his group of 

 sulphuretted ore bodies is admittedly not a natural 

 entity and contains examples of syngenetic, epigenetic, 

 and indeterminate modes of origin. This method of 

 dealing with the subject creates confusion rather than 

 clearness ; it is conglomeration, not classification. 



There are various mistakes in geography, which 

 should have been avoided ; for example, the Sierra de 

 Ronda is said to be on the Portuguese coast, and 

 Leadville in England ! Moreover, the work aims at 

 describing every deposit of importance, but there are 

 several notable omissions. 



No doubt there is room for a good, small text-book 

 on mineral deposits, but it will have to be on different 

 lines from those of the present one ; more care will 

 have to be devoted to classification and to the discussion 

 of the modes of formation of the deposits, and fewer 

 examples, and those only typical ones, must be quoted, 

 references to descriptions of others being generally 

 sufficient. It is probably only in this way that the 

 student can get a clear view of this complex subject. 

 The work at present before us does not fulfil these 

 conditions ; it may be of use for reference to the 

 experienced mining geologist who is not likely to be 

 led astray by it, but it is scarcely a safe book to place in 

 the hands of a beginner. 



H. Louis. 



NO. 2754, VOL. I TO] 



The Living Soil. 



Das Edaphon. Untersudmngen zur Okologie der 

 bodenbewohnenden Mikroorganismen. Von R. H. 

 France. Zweite Auflage. Pp. 99. (Stuttgart : 

 Franckh'sche Verlagsbuchharidlung, 1921.) 



EDAPHON " is the name which, from their 

 analogy to the plankton, Dr. France has 

 coined to cover all the forms of life occurring in the 

 soil. In spite of the very considerable amount of 

 work that has been done in recent years on these 

 organisms, very little of it is at present available to 

 the general biological reader. There are text-books 

 of agricultural bacteriology and a considerable number 

 of scattered papers dealing with single organisms or 

 groups of organisms from the soil, but most of these 

 reach only the specialist. Dr. France has therefore 

 performed a real service in writing a brief general 

 account of the soil fauna and flora, its conditions of 

 life, and the influences of the different groups of 

 organisms on one another and on the soil. 



As a general handbook to the subject, however, it 

 suffers from one considerable defect, for during the 

 past few years great advances have been made both 

 in this country and in America, of which apparently 

 Dr. France has as yet heard nothing, since he gives 

 no references to any non-German work of a later date 

 than 1912. Even a casual glance through recent 

 numbers of the English and American journals would 

 not only have given him many useful facts, but would 

 also have suggested methods of technique which would 

 have made his own investigations much more fruitful. 

 His accounts in particular of the insects and flagellates 

 give very little idea of the number and variety of 

 these creatures occurring in the soil. 



The observations on the ecology of the organisms 

 would also have been more satisfactory if a little more 

 statistical information had been given. It is not 

 very useful to be told that in May a cubic millimetre 

 of soil contained 15 organisms (omitting bacteria), 

 whereas in August the number had fallen to 3, unless 

 we are also told how much variation there is between 

 duplicate samples taken at the same time or at brief 

 intervals. Since Dr. France frequently reminds us 

 of the close analogy between the edaphon and the 

 plankton, one naturally recalls the wide divergences 

 found in duplicate catches of the latter. Probably he 

 is right in believing that the figures given are significant, 

 but the reader who wishes to understand what are 

 the effects of temperature, moisture, season, and the 

 physical and chemical properties of the soil on the 

 organisms living in it, is at a great disadvantage if he 

 is not told just what is the degree of significance. 



In spite of these defects, however, the present 



