percolating drop by drop through the
limestone crevices, dissolving the lime and forming the stalactites a
drop at a time through the years. How wonderful it was! He wished he too
might study. Perhaps, if he could make a go of his mother's fruit
ranch?--He was half asleep. He roused himself by trying to recall what it
was that Norris had told them about stalactites.

The rain water, charged with the carbonic acid gas of the atmosphere,
seeps in from the surface and falls drop by drop. Each slow drop remains
long enough upon the ceiling to deposit some of its dissolved lime in a
ring to which the next succeeding drop adds another layer.

In time this ring lengthens into a pipe-stem of soft lime. It fills and
crystallizes, thickens and elongates, as the constant drip, evaporating
from the outside, deposits more and more of the lime. Thus these stone
icicles are formed, sometimes an inch a year.

At the same time the drops that fall to the floor, solidifying one at a
time, build up a slender pyramid beneath,--a stalagmite,--which reaches
higher and higher as its stalactite hangs lower and lower. In time these
two formations meet in a slender pillar, the pillar thickens through the
same slow process and if the pillars stand close enough together,--as
where the drip follows a long rock fissure,--the pillars will eventually
join in a solid partition.

This _dripstone_, as the material of the formation is termed, began as
soft carbonate of lime; it hardens into _gypsum_ or, sometimes,
alabaster, or calcite.

The boy peered once more into the carved gallery, waiting till an
up-flare of the dying fire again illumined the fantastic ceiling, whose
fairy architecture gleamed opalescent in the orange glow. He thought of
the old fairy tales of gnomes hammering on their golden anvils in their
jeweled caves in the hearts of the mountains, and wondered if such lore
had not arisen from the fact of just such cave formations, coupled with
the echoes the slightest sound set to reverberating. After all, most folk
tales had some foundation.

Once these Mexicans were captured and the forest fire brought under
control, he meant to ask Norris if their camping expedition might not
include an exploration of some of the caves he had assured them
honeycombed this part of the Sierra.

He little dreamed in what fantastic fashion his wish was to come about,
as he lay there waiting till he could start his ride for help!

Nor did Pedro, drowsing