Now, because sequoia trunks are never wholly consumed in one forest fire, and those fires recur only at considerable intervals, and because sequoia ditches after being cleared are often left unplanted for centuries, it becomes evident that the trunk-remnant in question may probably have lain a thousand years or more.

And this instance is by no means a late one.
Again, admitting that upon those areas supposed to have been once covered with sequoia forests, every tree may have fallen, and every trunk may have been burned or buried, leaving not a remnant, many of the ditches made by the fall of the ponderous trunks, and the bowls made by their upturning roots, would remain patent for thousands of years after the last vestige of the trunks that made them had vanished.

Much of this ditch-writing would no doubt be quickly effaced by the flood-action of overflowing streams and rain-washing; but no inconsiderable portion would remain enduringly engraved on ridge-tops beyond such destructive action; for, where all the conditions are favorable, it is almost imperishable.

Now these historic ditches and root-bowls occur in all the present sequoia groves and forests, but, as far as I have observed, not the faintest vestige of one presents itself outside of them.
We therefore conclude that the area covered by sequoia has not been diminished during the last eight or ten thousand years, and probably not at all in post-glacial time.

Nevertheless, the questions may be asked: Is the species verging toward extinction?
What are its relations to climate, soil, and associated trees?
All the phenomena bearing on these questions also throw light, as we shall endeavor to show, upon the peculiar distribution of the species, and sustain the conclusion already arrived at as to the question of former extension.