Transcriber’s Notes
Reading edition
Retained publication information from the printed edition: this eBook is public-domain in the country of publication.
Where possible, UTF superscript and subscript numbers are used; some e-reader fonts may not support these characters.
In the text version only, text in italics is delimited by _underscores_.
In the text version only, superscript text is preceded by caret and delimited by ^{brackets}.
In the text version only, subscripted text is preceded by underscore and delimited by _{brackets}.
In the text version only, added a brief label to each illustration; and for graphs, provided tabular summaries of the data where possible.