--Retained publication information from the printed edition: this eBook
is public-domain in the country of publication.
--Silently corrected a few palpable typos.
--Moved illustrations to the nearest paragraph break.
--In the text versions only, text in italics is delimited by
_underscores_.
--In the text versions only, superscript text is preceded by caret.
--In the ASCII version only, subscripted numbers are preceded by
underscore and delimited by brackets.