—Retained publication information from the printed edition: this eBook
is public-domain in the country of publication.
—Silently corrected a few typos.
—Modified some references to plates for more convenient hyperlinking
(e.g., “Plate 17a & c” changed to “Plate 17a, 17c”).
—In the text versions only, text in italics is delimited by
_underscores_.