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which obtained in the Wisconsin and Missouri lead and zinc districts. 

 In the opinion of the authors, however, there are some differences as com- 

 pared with those regions. They beheve that the metals were formerly 

 disseminated chiefly in the Mississippian limestones, and that they were 

 quite largely leached out of these and carried downward and deposited by 

 downward circulation. The ores in the Boone chert formation are now 

 found principally along fissures, while in the Yellville dolomite they are 

 richest in the brecciated portions of the rock. Synclinal areas, on the 

 whole, appear to be the most productive. 



Secondary concentration by descending waters has certainly taken 

 place; whether concentration by ascending waters has also taken place is 

 not so clear. Messrs. Van Hise and Bain argue for an upward move- 

 ment as the chief factor in the deposition of these ores. 



Following the strictly geological part of the report is a more or less 

 detailed description of the mines and prospects in the area, with excellent 

 photographs and some valuable hints for the further exploration of the 

 country. 



The closing part of the paper is a rather general statement concerning 

 the correlation of the formations of the region. As a number of fossil 

 species, new to science, and many others not known outside of Arkansas, 

 were found, a more detailed treatment of the faunas of this region will 

 doubtless be forthcoming when Messrs. Ulrich and Girty shall have 

 completed their studies of the material collected. The accompanying 

 correlation table is a very helpful feature of the report. 



It is to be hoped that the further opening up of the area will so facili- 

 tate the work of geologists that more details concerning the actual occur- 

 rences of ore and concerning structural relations will become known. 



W. D. S. 



