—Retained publication information from the printed edition: this eBook
is public-domain in the country of publication.
—Corrected a few palpable typos.
—Re-arranged text in captions closer to the corresponding image.
—Expanded ambiguous references to illustrations, _e.g._ “Figure D” to
“Figure 16D”
—Added one section heading, “The First Big Lake” to match the table of
contents.
—Included a transcription of the text within some images, with estimated
scale readings from charts.
—In the text versions only, text in italics is delimited by
_underscores_.