INDUSTRIAL PROGRESS DURING THE YEAR 1873. H 



Census of the United States, accompanies his report. This 

 map, which was compiled by Professor C. W. Hitchcock and 

 Professor W. P. Blake, is on a scale of about ninety miles to 

 an inch (measuring only thirty-four by twenty-eight inches), 

 and, although confessedly incomplete, is the best geological 

 map which we have of the whole Union. The geological di- 

 visions are indicated by nine colors, representing, 1st, Eozoic ; 

 2d, Silurian ; 3d, Devonian and Lower Carboniferous ; 4th, 

 Coal measures; 5th, Triassic and Jurassic; 6th, Cretaceous; 

 7th, Tertiary ; 8th, Alluvial ; 9th, Volcanic. Professor Blake 

 has here given us for the first time a connected view of the 

 present state of our geological knowledge of the western 

 half of our country; while Professor Hitchcock, as General 

 Walker informs us, has made use, in the compilation of his 

 portion of the map, of a great quantity of material, " both 

 printed and in manuscript from the best geologists, collected 

 by him for the purpose of constructing a complete geological 

 atlas of North America," w^hich will probably soon appear. 

 In a future geological map of the United States, it will be de- 

 sirable to separate what is here called the Silurian into at 

 least four divisions : 1st, The Primal and Auroral of Rogers, 

 the Lower and Middle Cambrian of Sedgwick ; 2d, The Mati- 

 nal of Rogers, the Upper Cambrian of Sedgwick (these two 

 divisions being generally iHcluded under the erroneous name 

 of Lower Silurian) ; 3d, The Medina, Clinton, Niagara, and 

 Salina formations ; and, 4th, The Lower Helderberg consti- 

 tuting together the true Silurian. These four great groups 

 of strata, widely unlike in their distribution, their fauna, and 

 their geognostical relations, mark four well-defined periods in 

 the geological history of the continent. At a later time it 

 will be possible to subdivide in like manner the Eozoic rocks, 

 and to define the limits of the Laurentian, Huronian, Montal- 

 ban, and Norian series. 



Economic Geology and Mineralogy. The work of devel- 

 oping the deposits of crystalline iron ores, which lie on all 

 sides around the rim of the great paleozoic basin, has been 

 stimulated by the great rise in the price of English iron. 

 The amount of ore raised from the mines of Lake Superior 

 in 1873 was somewhat over one million of tons, equal to 

 two thirds that amount of metallic iron ; while the produc- 

 tion of crystalline ores from Missouri, New York, Canada, 



