course in such desert conditions there were practically no wild fruits.

"The Indians of the more fertile parts of North America, like the early
people of Europe, had wild vegetation to supply the means of subsistence.
And the wild vegetation also gave wild game a means of subsistence, to
say nothing of the means for clothing and shelter. Of course that is not
the whole of the story. There is, for instance, coal and iron, but iron
has to be smelted where there is forestation, and we come right back to
climate, as one of the principal factors in civilization.

"There is also energy,--zeal, determination. But what about the effect of
proper food and shelter on those qualities? And more important, what
about the effect of climate?

"Elaborate tests have been made. Without going into all that, perhaps you
will take my word for it. But the best climate for either physical or
mental efficiency is one that is variable,--for change is
stimulating,--and that goes to no unlivable extreme, but offers the cold,
dry winter and the warm, slightly rainy summer of, say, for instance, the
Eastern United States, or Central Europe, Italy, or Japan."

"But why does a winter in Southern California do an invalid so much good?"

"The change. The beneficial effects wear off with time.

"And just one word more, while we are on the subject. I'd hardly do my
old professor justice unless I mentioned that he lays that third factor
in civilization, inherent mental capacity, to the climatic conditions,
not of the present, but of the ancestral history of the past. But
remember, the climate of, say, Greece, has not always been what it is
to-day. Our Big Trees show, by an examination of their annual rings, the
same story that the rocks tell,--and that history tells,--that there have
been constant fluctuations of climate, within certain limitations. The
records of geology lead us to believe that California and the
Mediterranean countries have undergone the same climatic variations."

The next day the boys were so tired of sleuthing for the fire-bugs that
they decided to join the others in a holiday and explore one of the
neighboring peaks, leaving the burros and outfit at their camp of the
night before. About noon, the trail ended abruptly at a peak of granite
blocks each no larger than a footstool. Off to the left they could see a
peak higher than the one immediately before them. It seemed to be a ridge
of three peaks, theirs the middle one, and on