or less charged with mineral matter.  Evaporation goes on slowly, leaving the mineral behind.  This in time makes the immense columns, many of them thousands of tons in weight, which serve to support the roofs over the vast chambers.  I recollect that at one point in the cave one of these columns is of such huge proportions that there is only a narrow passage left on either side of it.  Some of our party became satisfied with their explorations before we had reached the point to which the guides were accustomed to take explorers, and started back without guides.  Coming to the large column spoken of, they followed it entirely around, and commenced retracing their steps into the bowels of the mountain, without being aware of the fact.  When the rest of us had completed our explorations, we started out with our guides, but had not gone far before we saw the torches of an approaching party.  We could not conceive who these could be, for all of us had come in together, and there were none but ourselves at the entrance when we started in.  Very soon we found it was our friends.  It took them some time to conceive how they had got where they were.  They were sure they had kept straight on for the mouth of the cave, and had gone about far enough to have reached it.