MURPHREE'S VALLEY; ECONOMIC GEOLOGY. 89 



but they are more tangible than the general descriptive 

 terms vast, unlimited, incalculable, and the like so often em- 

 ployed. 



The brown ores will be next considered. 



BROWN IRON ORES LIMONITES. 



There are six (6) different horizons in this valley that 

 carry Brown Iron Ore, or Limonite Ore, as it is more pro- 

 perly called. These, beginning with the lowest, and most 

 important are : 



1. The base of the Knox Dolomite, or base of Lower 



Silurian. 



2. A little below the middle of the lower half of the 



Knox Dolomite, or 400 to 500 ft. above its base. 



3. Near the top of the Knox Dolomite, but below the 



"Birmingham Breccia," where it exists. 



4. In the base, or lowest member of the Trenton. 



5. Near the top of the Siliceous Group, and beneath the 



LaGrange, or Oxmoor Sandstone. 



6. The top of the Sub-Carboniferous, or Mountain Lime- 



stone. 



The ore is not stratified, or generally continuous for any 

 great distance. It exists mainly as deposits, and these often 

 widely separated. But wherever found in large or small 

 quantities, in this or any of the other Silurian Valleys of 

 Alabama, it is in one or other of these six horizons, and 

 nevei scattered through any intermediate formation. Hence 

 bearing this important fact in mind, the hidden deposits of 

 this ore may be as systematically searched for and found as 

 the beds of the Red Hematite ores. 



When it is remembered that all, or nearly all, of the 

 brown ores that are known have been exposed by natural 

 agencies alone, it can hardly be doubted that many more 

 yet exist unknown, but which may be revealed by properly 

 directed search and effort. 



For the purpose of showing where the brown ores may 



