Well Paul, I'm glad you brought that up. Ever been to the Lost Sea in Sweetwater TN. Suppose to have the biggest underwater lake in the US. I went there on my second honeymoon, I've had three and don't want anymore. I was told that they use bat guano for their gunpowder in the caves there. The Confederacy manufactored it during the war. That place is awful dark down there when the guide turns off the lights.