624 Observations made in the Central Philippines. 
with each other, and were still soft and damp. How the birds had 
ever found this place so far from the light, with a dry face of rock, 
and with suitable digression in it was a wonder, and how they 
could do this work of nest building in such utter darkness. 
Coming to the surface we set out again, and after an hour’s tramp 
came to the second cave. This time as we were making our way 
down a steep, timbered valley, the path all at once dropped out 
before us, and we were at the mouth of a dark well, leading down 
almost perpendicularly for twenty or thirty feet at first, when the 
descent became more gradual. By clinging to the projecting rocks 
we clambered down, and soon found ourselves in a passage twenty 
feet high and as many broad. Great masses of rock had fallen 
from the roof, which made our progress slow. Curious stalactite 
growths, taking the form of flat plates with saw-tooth edges, were 
hanging from the roof. After making our way to a still greater 
depth and distance than before, we again heard the faint noise of 
the birds, not loud enough to be heard except in such perfect quiet 
as we were in. It seemed more like the sounds spirits might make 
than the notes of anything earthly. Soon after we came to a part 
of the cave where the roof was some eight or ten feet high, and 
worn into curious and very regular pits, five or six inches deep and 
as many wide at the mouth, and as smooth and round as if made 
artificially. In these the birds were building their nests, attaching 
‘them to the walls of the pits. Again, in spite of the weak protests 
of the owners, the nests were torn out and appropriated by our 
guide. 
As we made our way out we passed a stalactitic column a foot 
in diameter, which had connected the roof and floor of the cave, 
but had been broken across by earthquake, and the ends separated 
by half an inch. The thought of being caught away in there 10 
utter darkness by an earthquake, with the rocks grinding and shut- 
ting in upon us, was anything but pleasant. Near the mouth of 
the cave, just where we could begin to perceive a ray of light 
from the surface, were several nests of cruder, rougher make, bemmg 
much larger and made chiefly of grass and lichens stuck into the 
face of the rocks by large masses of the edible gum. The birds 
are, without doubt, of the same species. The guide said they were 
sentinels to alarm those within, and that their nests were always 
