7 o8 SCIENCE PROGRESS 



translator falls in with British and Colonial practice rather than American in 

 choosing " lode " as the equivalent. He points out that the German Ader more 

 nearly expresses what we mean by vein —that is, an occurrence of lesser magni- 

 tude than a lode. Seifen is translated "gravel-deposits" in preference to " placers." 

 Sahlband is translated as "gouge," and Gangtonschiefer as "flucan." With this 

 choice of English equivalents we are in general agreement. 



The translator throughout betrays some unfamiliarity with petrological terms. 

 He uses the term "sodium " where " soda " is meant in many compounds such as 

 "soda-augite-syenite." No doubt the huge compound petrological terms on p. 250 

 and elsewhere are taken from the original German. Mistakes and misprints are 

 commendably few. The atomic weight of platinum is given as ranging between 

 14 and 19 (p. 83) instead of the specific gravity as obviously meant. Aluminium 

 is referred to as a mineral on p. 152, whilst on the same page there appears to be 

 a misstatement as to the amount of thorium in the rare earths. The term 

 " ilmenitite " has frequently been misspelt (pp. 252-3), as also has " pyrrhotite " 

 (p. 301), and " limonite" (p. 218). 



This volume contains a general discussion of ore-deposits, which occupies the 

 first half of the book. The second half contains the detailed descriptions of the 

 ore-deposits due to magmatic segregation, contact-metamorphism, and the tin and 

 quicksilver groups of the ore-bodies classified under lodes, irregular cavity fillings, 

 and metasomatic deposits. Early in the book, in connection with form and 

 graphic representation, the ore-deposits are classified as syngenetic, originating 

 with the country-rock, and epige?ietic, arising from later processes ; but these 

 terms are abandoned in the more extended discussion of classification that occurs 

 later on. The close connection between ore deposits and igneous rocks is accepted 

 as axiomatic, and the authors finally adopt a classification with four main groups 

 on a genetic basis, which also brings into prominence the degree of closeness of 

 the connection of the deposits with their original igneous source. The four groups 

 are : (1) Magmatic Segregations, due to concentration of metalliferous minerals in 

 a molten magma, which represent ore-deposits nearest to their original source ; 

 (2) Contact-deposits, formed by endomorphic and exomorphic contact-meta- 

 morphism at the margins of intrusive igneous masses ; (3) Fissure cavity-fillings, 

 irregular cavity-fillings, and metasomatic deposits, which represent different 

 phases of the activity of aqueous solutions emanating at some distance in time and 

 space from an igneous intrusion ; and (4) Ore-beds, sediments more particularly, 

 but including also some doubtful bedded deposits. In these the ore material is 

 remote from its original source, and generally has no direct connection at all with 

 igneous rocks. This grouping does not possess the sharp physico-chemical 

 definition of the classification developed by Lindgren, but it is doubtful whether 

 the latter can be applied in many cases. 



No treatise on ore-deposits, not even Lindgren's, has yet given a full account 

 of the valuable microscopic methods of investigation of ore-deposits. In this 

 book there is no adequate treatment of this subject. The microscopic criteria 

 which give the order of succession of the minerals in igneous rocks are frequently 

 not applicable to ore-deposits. In the latter the complete inclusion of one mineral 

 within another is not evidence for the priority of the included mineral, as is the 

 case in igneous rocks, since it may have grown by metasomatic processes within 

 its host. Many points similar to this require to be formulated in order to establish 

 the microscopic study of ore deposits on a more secure basis. 



From the association of Vogt in the authorship of this work, it was to be 

 expected that the ore-deposits due to magmatic segregation would be very fully 



