AMERICAN GEOLOGY — DECADE OF L850-1859. 4V>1 



chloritic schists, semiporphyritic, arenaceous grits and conglomerates, 

 and jaspery and plumbaginous slates," carrying veins and dikes of a 

 metalliferous character. 



He recognized the difficulty in at all times separating the Azoic 

 rocks from the overlying genuine Paleozoic, and also the fact that it 

 might at times grade into it without a break. Also he recognized 

 the fact that a portion of his Lower Paleozoic was metamorphic or 

 semimetamorphic. When one reflects on how emphatically Rogers 

 combated Emmons's Taconic system, it seems strange that he should 

 hold to these views. 



The belt of metamorphic and semimetamorphic strata extending 

 from Newfoundland to Alabama he designated as the Appalachian or 

 Atlantic Belt, and the one extending westward from the north coast 

 of the St. Lawrence Gulf to the Great Lakes as the Laurentide, 

 owing to the fact that these latter rocks were well developed in the 

 Laurentide Mountains. 



The semimetamorphic Azoic rocks he considered as richer in miner- 

 als than the true gneisses, and to these he referred the schists of the 

 Atlantic coasts, bearing lead, copper, zinc, and iron, and the auriferous 

 quartz veins of California. 



The Paleozoic formation proper, which was estimated to cover prob- 

 ably one-half of the total area of the United States and to have a total 

 thickness of from 30,000 to 35,000 feet, was divided into fifteen distinct 

 series or sets of formations, "extending from the deposits which wit- 

 nessed the very dawn of life upon the globe to those which saw the 

 close ^i' the long American Paleozoic day." The names assigned to 

 these formations he regarded as "significant of the different natural 

 periods into which the day divides itself, from the earliest dawn to 

 twilight." These were, beginning with the oldest, Primal, Auroral, 

 Matinal, Levant, Surgent, Scalent, Pre-Meridian, Meridian, Post- 

 Meridian, Cadent, Vergent, Ponent, Vespertine, Umbral, and Serai — 

 signifying the Dawn, Daybreak, Morning, Sunrise, Ascending day, 

 High morning, Forenoon, Noon. Afternoon, Waning day. Descending 

 day, Sunset, Evening, Dusk, and Nightfall. These terms, based on 

 time, he considered preferable to the inexpressive ones, mainly of a 

 geographic character, then in vogue. 



The Primal, Auroral, and Matinal were regarded as the approximate 

 representatives of Sedgwick's Cambrian; the Levant, Surgent, Scalent, 

 and Pre-Meridian, near representatives of the English Silurian, begin- 

 ning with the Upper Caradoc Sandstones. He recognized both a 

 physical and paleontological break in the succession of strata at the 

 contact of these two great divisions of the Paleozoic system. At the 

 base of the Carboniferous he thought to recognize a break correspond- 

 ingly sharp. 



