About a dozen of us got leave of absence for a day, provided ourselves with candles, provisions and hatchets, and set out for this cave. Near its mouth was an old saltpetre manufactory, dismantled by the rebels when compelled to abandon it. The nitre was obtained from a brown earth brought from the cave--said to be very rich. This cave is provided with the inevitable stream of water running through it, and the obvious inference is that this is the active agent in producing the cave,--the stream providing itself a channel through the heart of the mountain by finding and dissolving out the softer portions. We entered a long flat boat and were wafted by push poles some half mile into the cave where we found our stream issuing from beneath some rocks too low for the boat to pass under. We accordingly landed and began such an exploration as our limited time would allow. The cavity divides and subdivides into a vast number of passages which cross and recross each other, forming a net work of dark alleys that are very bewildering. Some of them are said to be over five miles in length. We selected one and followed it to the end, marking with our hatchets each branch or cross road--so that we might return the same way without getting lost. Judging by the time consumed we must have traveled about three miles. In places the ceiling came so low that we had to lie down and walk like a snake a short distance, emerging a vast hall, perhaps fifty by two hundred feet and from ten to thirty feet high. The countless beads of moisture hanging from the stone ceiling would flash back our lights with a sparkle suggestive of a cave of diamonds. Our route alternated between narrow winding passages and immense auditoriums--where an ordinary tone would be exaggerated into a roar. In many of these the ceiling was hung with stalactites, resembling an inverted forest, varying from the smallest quill-like pendant--through all gradations of size to those that would weigh hundreds of pounds, which when struck sharply with a hammer would sing out in tones like a Cathedral bell. I gathered a fine stalactite about the size and length of an ordinary lead pencil, a perfect cylinder in shape, pure white and hollow for half its length. I tried hard to preserve it, but it was very frail and did not survive the fortunes of war. We arrived at the end of our passage about noon, and there we ate our dinner in a magnificent stone dining hall, in which a regiment could eat without crowding. It was shady and cool. Not far from where we dined was bat headquarters, where about a bushel of these nocturnal birds had their rendezvous. Some were hanging to the ceiling, others hanging to them, and others to them, &c., an inverted cone of acro-bats. We took a can, we had just emptied of peaches, and filled it with bats and took them into camp as living witnesses of our visit to their home. The first and last time I was ever engaged in the canning of meats.