14 PROCEEDINGS OF THE DENVER MEETING 



The cap-rock of this division is recognized in the water gap of Big Emory near 

 Harriman ; hence a name I have given to it, the " Emory sandstone." * 



The topography of the tableland which marks out the Bon Air and Tracy City 

 divisions is more characteristic in the western portion, where the strata are hori- 

 zontal or but little inclined, than in the eastern. In the eastern it is mostly ob- 

 scured by the folds and displacements of the strata. 



On the Tracy City divisions rests the Brushy Mountain measures, not much if 

 any less than 2,000 feet in thickness, a great series of shales and sandstones, with 

 very little limestone. These include not less than 14 coal horizons, half of which, 

 or thereabouts, are coalbeds of workable thickness. The Brushy mountains are 

 a great mass of mountain ridges, sharp crested, and reaching 1,400 to 1,800 feet 

 above their bases. They are confined to the northeastern counties of the coal- 

 fields. 



These measures rest in turn, descending, on the Tracy City and Bon Air meas- 

 ures. A drill driven down vertically from one of the high peaks of the Brushy 

 Mountain measures to the mountain limestone at the base of the entire coal series 

 would pass through the strata of the three subdivisions for a distance of nearly 

 3,000 feet. 



Middleton is a Tennessee name ; hence the adoption of " Middleton-Clayton." 

 Another name is Midway, f 



The remaining formations explain themselves and need no comments. 



HORIZONS OF PHOSPHATE ROCK IN TENNESSEE 

 BY JAMKS M. SAFFORD 



The object of this note is to point out the different horizons o£ phosphate rock 

 observed in middle Tennessee. There are four of them, all of which are regularly 

 stratified or are the residues after leaching of regularly stratified rocks. In addi- 

 tion, there is a fifth occurrence comprising irregular deposits, formed — travertine- 

 like — by precipitation from solution. 



The following enumeration and summary is in part from a small school book, 

 " The Elements of the Geology of Tennessee: " % 



The Mount Pleasant, of Nashville or Trenton age, occurs over a wide extent of 

 country; rock of high grade, mined cheaply in open excavations; production 

 great and increasing. 



The horizon of the Hudson, of the Hudson or College Hill age, is near or at the top 

 of the Lower Silurian limestone and from 100 to 200 feet above the Mount Pleasant 

 rock. Near and north of Nashville it is found at the tops of the hills; occurs in 

 large quantities in Sumner county, also in Hickman county, occupying a lower 

 topographical level, and, like the Mount Pleasant, mined in open excavations; 

 production considerable and increasing. 



The Swan creek, a division of the Devonian period, lies in the hills, like a bed 

 of stone coal, and but little above the horizon of the Hudson— in fact, at Tottys 



*See Elements, pp. 151. 



fSee vol. I, Bulletins of American Paleontology, no. 4; The Midway Stage, by G. D. Harris, 

 Cornell University, Ithaca, New York. 



JThe Elements of the Geology of Tennessee, prepared for the use of the schools of Tennessee. 

 J, M. Safford and J. B, Killebrew, Nashville, Tennessee, 1900, p. 142. 



