78 PROCEEDINGS OF THE CANADIAX INSTITUTE. 



These beds from the Siliceous to the Trenton are continuous across 

 the ends of tlie Basin, and are also found in place upon its western 

 side. The Trenton is continuous across the Basin and with the Nash- 

 ville rocks forms its bottom. 



If we now turn to the sections as exposed upon the north, west 

 and southwest sides of the Basin we will find that while all the for- 

 mations as exposed upon the east are to be found x-epresented in these 

 sections, with an equal regularity we have another set of beds to deal 

 with which are not to be found anywhere along the eastern side of the 

 Basin, and which owing to their interposition lie unconformably to 

 those underneath. These are the Niagara, including the Clinton and 

 Medina. They are interposed in their proper position in the geo- 

 logical scale between the Nashville or Hudson Paver formation and 

 the Black Shale. 



It is chiefly the uppermost part of the Niagara formation that is 

 found in ^Middle Tennessee. The Meniscus limestone of Di-. Saflbrd's 

 Report consists of thick-bedded crystalline and fine-grained limestones 

 laore or less argillaceous and often weathering into shale. Most of 

 the limestones are sparry and crinoidal ; many contain green points. 

 The series is divided into an upper or sponge-bearing bed and a lower 

 or variegatad bed, and each about 100 feet in thickness. This lower 

 bed is an alternation of grey, red and mottled layers, and much tends 

 to crumble into shales. The limestones of the uj)por bed are light 

 grey and light bluish grey, and much of the Vjed weathers into shaly 

 matter. 



Where this formation is firat met with in the slope of the western 

 side of the Basin it is not in very great foi'ce, but generally only in the 

 shape of a feather edge, or running out, but increasing in thickness in 

 a westerly direction, or towards the valley of the Tennessee River. 

 This feather-edged Meniscus bed is first found in tlie northern side of 

 the Basin in the western part of Macon County and upon the .south- 

 ern side of the Basin it first appears in Lincoln. From Lincoln it 

 passes through the south-west part of Bedford County and through 

 the Counties of Lawrence, Lewis, Maury, Williamson, Davidson and 

 Sumner in a sort of semi-circular course until it reaches the place of 

 its fii*st northern appeai'ance in Macon County. 



From this line westward until the old shore line west of the Ten- 

 nessee River is reached the Niagara formation is represented in the 

 geological scale of the State of Tennessee. 



