90 Scientific Intelligence. 



phases of volcanic activity and also of the rapidity of erosion in 

 volcanic materials, and the ease with which vegetation in tropical 

 countries takes possession of a region which is absolutely barren* 

 The sixteen plates from well selected photographs are excellent, 

 and when compared with those taken in 1902 from approximately 

 the same localities, constitute a history of stream development, 

 erosion, and changes in volcanic materials which is very striking 

 indeed. The present volume also contains the "Petrographical 

 notes on the products of the eruptions of May, 1902, at the 

 Soufriere in St. Vincent," by John S. Flett. The scientific world 

 is fortunate in having these volcanoes studied by Anderson, La 

 Croix, Hovey, and Heilprin, whose combined reports constitute 

 perhaps the most elaborate treatise on any single volcanic disturb- 

 ance in the world's history. The bibliography which accom- 

 panies the report is fairly complete, but fails to mention the 

 writings Of one of the most industrious students of this district, 

 viz., Angelo Heilprin. h. e. g. 



9. The Geology and Ore deposits of the Coenr oVAlene Dis- 

 trict, Idaho ; by Frederick Leslie Ransome and Frank Cath- 

 cart Calkins. Professional paper 62. U. S. Geological Survey. 

 Pp. 203, pis. xxix, figs. 23. Washington, D. C, 1908. — This 

 report is of great interest to geologists since it embraces an area of 

 404 square miles constituting the well known Coeur d'Alene min- 

 ing district of northern Idaho and gives the detailed strati- 

 graphic and structural geology of a portion of a region concern- 

 ing which but little has been previously known. 



The district, as shown by the map, is one of maturely dissected 

 mountainous topography showing a relief between river bottom 

 and mountain top of about 4000 feet. It lies in the midst of a 

 region which while not attaining elevations as great as certain 

 others in the Cordillera, yet is, on the whole, of a particularly wild, 

 rugged and forested character. The sedimentary rocks except 

 for the surface gravels belong entirely to the great Algonkian 

 system known as the Belt, from the earlier studies in the Belt 

 mountains of Montana. The section here attains a thickness of 

 17,200 feet, the base not exposed and the top removed by erosion. 

 They vary from sandstones to argillites and throughout the 

 greater portion of the system the argillaceous formations show 

 marks of shallow water deposition and subaerial exposure. No 

 great limestone formations such as the two which occur farther 

 east are found in this region and it is concluded that the sedi- 

 ments came from the west. A great fault, however, whose out- 

 crop at the surface is known as the Purcell trench cuts off the 

 system to the west, beyond this a highly metamorphic complex 

 being exposed. The igneous rocks are all intrusive, the large 

 masses varying from monzonites to syenites. The region is com- 

 plexly folded and faulted but, as in other portions of this province, 

 the rocks are remarkably free from regional metamorphism, giv- 

 ing unusual opportunities for studying an Algonkian system. 



The mineral resources in the order of their present importance 

 are (1) lead silver ores, (2) copper ores, (3) gold ores. j. b. 



