E-text prepared by David Starner, Keith Edkins, and the Project Gutenberg Online Distributed Proofreading Team (http://www.pgdp.net)
Transcriber's note:
A few typographical errors have been corrected: they are listed at the end of the text.
In mathematical formulae the carat (^) and underscore (_) introduce superscripts or subscripts respectively, of one character or a group enclosed in curly braces ({xyz}). Elsewhere underscores delimit italics in the text, and braces enclose the original page numbers thus {123}.
