26 TACONIC SYSTEM. 



increased by the addition of numerous synonyms — the ready weapon to which igno- 

 rance resorts. 



§ 47. In 1863 G. F. Matthew named the rocks exposed at St. John, New 

 Brunswick, the " St. John Group." He described them as arenaceous, argillaceous, 

 and carbonaceous shales, and clay slates; often sandy, with sandstone and quartzite, 

 having a thickness of 4,500 feet, and having an exposure about 30 miles long and 

 4 miles wide. He collected Paradoxides, Conocoryplie, Obolella, Ortfiis, OrUiisina, 

 Stenotheca, Hyolithes, and languid. In 1865 he and Bailey and Hartt correlated 

 these rocks with the slates of Vermont having Elliptocephala asaphoides, and the 

 schistose beds at Braintree, Mass., holding Paradoxides harlani, and thus proved their 

 "St. John Group" to be a synonym for Emmons's "Black Slate," in the Upper 

 Taconic System. Furthermore, they identified the slates with some found in New- 

 foundland containing Paradoxides and Coiiocoryphe. Later they divided the Lower 

 Taconic of New Brunswick, which they called Huroniau, into the " Coldbrook 

 Group," the " Coastal Group," and the " Kingston Group," and estimated the thick- 

 ness as exceeding 10,000 feet. 



§ 48. The Vermont Geologists in 1861 called the Black Slate, Taconic Slate, 

 and Roofing-slate of Emmons the "Georgia Group." The name has priority over 

 the "St. John Group," and if the Taconic System is to be divided into Groups with 

 geographical names, and these three divisions of Emmons are to be thrown together 

 in one Group, then they must under the laws of nomenclature bear the name of the 

 Georgia Group. The Black Slate has, however, been called the Swanton Group, and 

 if this name should become desirable then the Upper Taconic would be divided into 

 the Swanton Group and the Georgia Group, and their maximum thickness in Ver- 

 mont exceeds two miles. This division is that adopted by Perry, who has shown the 

 Potsdam sandstone rests directly upon the Swanton Group, or Black Slate, as 

 originally asserted by Emmons, and that both the Swanton Group and the Georgia 

 Group are fossiliferous. 



§ 49. The Taconic rocks extend from Canada East and Maine to Georgia and 

 Alabama, flanking almost continuously the ranges of mountains upon both the 

 eastern and western slopes. Their thickness in New Hampshire is over four miles, 

 and in Vermont the maximum must exceed five miles. The slate belts of York 

 and Lancaster Counties, Pa., and the rocks containing the valuable ores of nickel 

 and copper belong to this System. There are five extensive outcrops in North Caro- 

 lina, and three or four subordinate ones. They rest unconformably upon the belts 

 of the exposed Laurentian, and very much resemble in their character the sub- 

 divisions in Vermont and New York. The largest outcrop is from twenty to forty 

 miles wide, and extends quite across the State. The maximum thickness exceeds 

 five miles. There are large outcrops in Virginia, South Carolina, Georgia, and 

 Tennessee, and limited outcrops in Alabama. Gold, silver, copper, lead, iron, and 

 other valuable minerals, occur in these rocks not only in veins, fissures, and dykes, 

 but in seams following the stratification and as part of the sedimentary materials. 

 In Northern Georgia gold exists in seams, with milky quartz, following the strati- 

 fication of hornblende schists, and constituting as truly sedimentary rocks as the 

 schists themselves do. The seams are stratified within the slaty sediments, and are 

 of the same age as the Taconic System. These seams are so constant they char- 

 acterize the slates or schists in the Appalachian System. They are metalliferous, 



