A correspondent writes referring to Mark Twain's works _Life on the
Mississippi_, _The Adventures of Tom Sawyer, and _Adventures of
Huckleberry Finn_:

~~~~~
It seems to me that one of the major themes of these works, as well as
the others I have read and re-read is an abiding passion for the
environment and nature.  I have viewed Twain as a humorist, social
commentator, editorial writer, travel writer, but never as a nature
writer.  Is he not our first John Muir, Aldo Leopold, Rachel Carson, etc?
Are there any books or articles that you know of that touch upon
this aspect of his writing?

~~~~~

I find references in _Mark Twain's Library: A Reconstruction_
to Henry David Thoreau and Dean Sage -- environmental writers
who Twain admired. Are there any recommended journal articles
or essays that address this aspect of Mark Twain's works?

Thanks,
Barb