I'd have to go back and reread either my notes, or the book, but my
general *sense* is that the reason they didn't use explosives to close up
the door centuries ago was that they didn't have such explosives to use.

Certainly not among the native american population of the time.

Actually, hardcover or soft, the book is out of print, and thus I
no longer get royalties on the book.

There are, as you say, certain themes in my work that tend to recur,
because I'm still trying to get a handle on them...why do we do the thigns
(things) that we do? What are the hairline fractures in our personalities
that cause one person to become a Mother Theresa and another to become a
serial killer? What are the choices between here and there? Basically,
the fundamental questions of who are we, what are we doing here, why are
we doing what we're doing, where are we going, and what shall we do when
we get there?

jms