"Biggest thing I ever saw underground," I answered. "Seems like we're suddenly in another world. Notice that peculiar odor?" Lynn, who had been the most quiet of our trio, spoke up. "Animals of some kind," he said. "But I wouldn't know just what." As we proceeded further the smell became stronger and more pronounced. Our caution increased, for I know all of us expected at any moment to see some animal lunge out at us. We kept our eyes open and, with the torch held above our heads, were able to see several feet ahead of us. Beyond that the outline of any object was too dim for us to definitely make out what it was. The animal odor was getting stronger. We were definitely nearing something, but just what I didn't know. As a result of this uncertainty we slowed our pace, stopping every few feet to listen for any sound, yet nothing did we see or hear. At any moment I was sure we would see two moving balls of light race toward us, which would indicate the eyes of some wild animal, but as we progressed further inside the cave our fears were unfounded. Finally the smell became quite pronounced and at the same time we came upon huge mounds of something which was unlike the rest of the floor of the cave. I glanced upward, and on the walls and ceiling of the cave I had the answer to the smell. "Bats!" I exclaimed. "Millions of them. This is where they live. And those mounds beneath them are the result of their living here. Why, there's enough fertilizer there to ..." I didn't finish the sentence. As far as the eye could see, which wasn't too far in that dim light, there were piles and piles of guano, which is the commercial name for fertilizer created by animals of this type. Now our fears were ended, as we felt relatively safe from bats, even though there must have been millions right there over our heads. Now they were asleep, but shortly after sunset we knew they would suddenly come alive and head for the cave entrance, where they would fly off into the night in search of food. By morning they would again form that black, funnel shaped cloud I had watched previously as they re-entered their home--a home that must have been theirs and theirs alone for countless centuries--if the huge piles of guano at our feet was any indication, and it surely must have been. In places these piles of bat deposit reached almost to the top of the cave. Later we found that this guano reached almost a quarter of a mile in length and stretched some 75 feet in width. Some of the piles later proved to be over a hundred feet deep! Even the crudest calculation would have shown that there was enough guano here to merit the cost and trouble of getting it out of the cave and selling it commercially. At that moment I decided to stake a mining claim on the cave.