The Stygian caves are still farther up the mountain,--little pockets
in the rocks, or well-holes in the ground at your feet, filled with
deadly carbon dioxide. We saw birds' feathers and quills in all of
them. The birds hop into them, probably in quest of food or seeking
shelter, and they never come out. We saw the body of a martin on the
bank of one hole. Into one we sank a lighted torch, and it was
extinguished as quickly as if we had dropped it into water. Each cave
or niche is a death valley on a small scale. Near by we came upon a
steaming pool, or lakelet, of an acre or more in extent. A pair of
mallard ducks were swimming about in one end of it,--the cool end.
When we approached, they swam slowly over into the warmer water. As
they progressed, the water got hotter and hotter, and the ducks'
discomfort was evident. Presently they stopped, and turned toward us,
half appealingly, as I thought. They could go no farther; would we
please come no nearer? As I took another step or two, up they rose and
disappeared over the hill. Had they gone to the extreme end of the
pool, we could have had boiled mallard for dinner.