Art X.] Watson, Yclloiv OcJier-Deposits of Georgia. 



205 



Atlanta, Georgia, of specimens of the rock collected by me 

 from different exposures of the formation. 



Silica, 

 Alumina, . 

 Iron sesquioxide, 

 Iron disulphide, 

 Lime, 

 Magnesia, 

 Soda, 

 Potash, . 

 Manganese oxide. 

 Titanic oxide, . 

 Barium sulphate, 

 Water, 



Total, 



Per (_'ent. 

 90.36 



1-52 

 0.57 



0.4.5 

 0.16 

 none 

 0.07 

 4.46 

 0.31 



99.92 



Attention is called in the analysis to the percentages of 

 iron disulphide (pyrite) and barium sulphate (barite) present in 

 the rock. The occurrence of pyrite in the rock has been re- 

 ferred to above. The mineral barite is present to a greater or 

 less extent in all the ocher-deposits of the district, but its pres- 

 ence in the fresh rock as a mineral constituent is nowhere indi- 

 cated, either macro- or microscopically. The very small per- 

 centages of lime and alkalies shown in the analysis confirms the 

 microscopic study of a large number ot thin sections of the rock, 

 in the nearly complete absence of feldspars. A few thin sec- 

 tions, however, showed sporadic grains of both microline anci a 

 striated plagioclase. 



Topography. 



With respect to surface](configuration, the district may be 

 divided into two nearly equal, unlike areas, as indicated on the 

 accompanying map, Fig. 2. The line separating these two 

 areas is an irregular one roughly paralleling the fault-line, and 

 located from one to three miles west of it, and marking the 

 contact between the Weisner quartzite and the Beaver lime- 

 stone. The contour lines on the map, Fig. 2, mark off quite 

 strongly the dividing-line between the two unlike areas. 



That part of the district north of the Etowah river and 



