Well... Eric NJ finally invoked a response from the professor at University of TN., Dr. Jan Simek. He stated... "Hi Erik, I have had a chance to look at the photos, but I've been out of town a lot, so haven't been able to get back to you. Without being there in front of these features, the mud mounds look to me to be sediment casts from saltpeter vats, and well-preserved ones at that. Originally, there would have been wood planks around the outside and wooden drains underneath, but often those would have been removed and taken elsewhere by the miners after they were finished with a particular vat. The size, shape, and regularity of the mounds in your cave all support this interpretation. The likely times for saltpeter mining in Tennessee are: early around the War of 1812, during the Crimean War when gunpowder was scarce--the 1850s, and during the Civil War when the Confederate Niter Bureau was seeking sources to make powder for the southern armies.
It's very hard to tell about the markings on the outside of the mounds...some are obviously letters and/or names, but I just don't see them very well in the photos. Obviously, if the mounds are vats, then the markings were made after the planking was removed, i.e., historically. Hope this helps... Jan F. Simek, ... President Emeritus... Distinguished Professor of Science... Department of Anthropology... 252 South Stadium Hall"
So Eric got back with Mr. Simek to supply some more information. It's hard to actually believe miners worked in such cramped quarters. I tried to Google examples of "Sediment casts from saltpeter vats" but I couldn't find any pics to compare. If somebody can or does find an example please post so we can compare. This mud/clay mound is right up against the wall and ceiling so this explanation is hard to grasp. But again... I'm only guessing. I've never mined for saltpeter (duh). And then throw in the symbols etched upon it and it becomes even more confusing. Maybe the letters but not the symbols...? So if anyone has any good info concerning saltpeter vats and mining and how small an area they'd work in PLEASE share... Thanks, Brad