546 THE JOURNAL OF GEOLOGY. 



After discussing the eruptive origin and theory of chemical deposit 

 which have been advanced to explain the occurrence of these ores, the 

 writer argues that they are formed from beds of glauconite, and gives 

 a rather lengthy discussion of the occurrence, structural features, and 

 decomposition products of glauconite. He sums up his conclusions 

 as follows : 



i. At the beginning the rock was probably of sedimentary nature, 

 consisting mainly of glauconitic grains with probably some associated 

 calcareous and siliceous matter. 



2. The elevation of the beds exposed them to atmospheric agencies 

 which decomposed the glauconite into silica and iron oxide. 



3. The various stages of decomposition and certain reconstructive 

 processes have produced the present phases of the iron-bearing rock. 



4. The iron is concentrated in the regions of greatest oxidation ; 

 the silica in the rearions of least oxidation. T. C. Hopkins. 



The Mineral Industry, its Statistics, Teclinology, and Trade in the 

 United States and Other Countries, from, the Earliest Times to the 

 end of i8gj. Annual. Vol. II., pp. 894 + xl., and six 

 plates. Price $5. R. P. Rothwell, Editor, Scientific Pub- 

 lishing Co., N. Y. 



Volume II. of the Mineral Industry, while following the general 

 plan of the first volume, covers several new topics and discusses some 

 of them at greater length, so that there is increase in size of more than 

 a third over the first volume. The fact that but little of the first 

 volume is repeated in the second, makes both necessary to those 

 interested in the mineral industry from either a commercial or 

 scientific standpoint. To the economic geologist they are indis- 

 pensable. 



" Its statistics, technology, and trade " describes the aim of the 

 work, but these terms hardly stand in the order of their relative 

 importance as treated in the volume. As it takes the place of the 

 annual statistical number of the Engineering and Mining Journal, it is 

 probable that statistics was the primary object in the mind of the 

 editor. But in the two volumes published the statistical feature is 

 overshadowed by the others ; this, however, is not to be regretted, as, 

 instead of being merely reference tables of production, they form 

 convenient handbooks to which the scientist as well as the tradesman 



