—Retained publication information from the printed edition: this eBook
is public-domain in the country of publication.
—Added a Table of Contents.
—Relocated all image captions to be immediately under the corresponding
images, removing redundant references like “preceding page”.
—Silently corrected a few palpable typos.
—This book was printed mostly in italic, with emphasized text in roman;
the eBook reverses those fonts.
—In the text versions only, text in roman is delimited by _underscores_.