456 Harper : Collection of Plants in Georgia 



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both wholly in the Palaeozoic region. The principal points of 

 interest visited during the remainder of July were the Chattoogata 

 Mountains, a few miles west of Dalton, and Gordon Springs, in the 

 extreme western part of Whitfield county, at the base of Taylor's 



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the 25th to the 28th, crossing the ridge into Walker county, two 

 or three times. The summits of these higher ridges in Whitfield 

 county, are composed of sandstone rocks, of the Red Mountain (or 

 Rockwood) formation, which represents the upper portion of the 

 Silurian in Georgia. The lower ridges are mostly of the Knox 

 Dolomite and Chickamauga formations (Lower Silurian). 



During these trips in the latter part of July I collected my 

 numbers 242-324, and Mr. Wilson his numbers 62-160. 



Having decided to explore the still higher mountains of the 

 Lookout plateau to the west of us, we set out on July 3 1 and 

 walked across Chattoogata, Taylor's, and several smaller ridges, to 

 Lafayette, the county seat of Walker county, about 25 miles west 

 of Dalton. With Lafayette as a base, on the first three days of 

 August we made trips to different portions of Pigeon Mountain, a 

 few miles to the westward, and also collected several plants in the 

 immediate vicinity of Lafayette, which is in a valley of Oostanaula 

 (or Connasauga) shale, a part of the Cambrian formation. 



Pigeon Mountain is a spur of Lookout Mountain, and, like 

 Lookout, is a synclinal plateau, capped by coal measures (Car- 

 boniferous). The rock of the coal measures here is a sandstone 

 scarcely distinguishable from the Red Mountain sandstone. Below 

 the coal measures the Mountain (or Bangor) Limestone is exposed 

 over a large area on the lower slopes of the mountain. This is a 

 compact bluish limestone, and many interesting plants are found 

 on it. Below the carboniferous rocks is a stratum of Devonian 

 rocks about 25 feet thick, known as the Chattanooga Black Shale. 

 This outcrops all along the base of the mountain, but is rarely 

 visible, on account of the ease with which it disintegrates where 

 exposed. 



The highest point of Pigeon Mountain is 2329 feet above sea 

 level, and about 1400 feet above the adjacent valleys. On the 

 first of August we ascended to this high point, and made the ac- 

 quaintance of some of the rare plants of this mountain region. 



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