Transcriber’s Note
Punctuation, hyphenation, and spelling were made consistent when a predominant preference was found in the original book; otherwise they were not changed.
Simple typographical errors were corrected; unpaired quotation marks were remedied when the change was obvious, and otherwise left unpaired.
Illustrations in this eBook have been positioned between paragraphs and outside quotations. In versions of this eBook that support hyperlinks, the page references in the List of Illustrations lead to the corresponding illustrations.
Footnotes, originally at the bottoms of pages, have been collected, renumbered, and placed just before the Index.
The Index was not checked for proper alphabetization or correct page references.
Some values in the original book are known today to be incorrect, but have not been changed here.
Page 133: The last equation on the page,
μ = μ₀ (1 + .00275 t - .00000034 t²)
was misprinted as
μ = μ₀ {1 + .00275 t .00000034 t²}.
It is shown here with corrections based on its cited source:
https://archive.org/details/s05philosophicalmag21londuoft/page/212
Page 144: “possibly of ether atoms bound with them” was printed that way, but “ether” may be a misprint for “other”.
Page 170: “hence at C, where they touch” was printed as “A”, but Figure 1 at that point is labelled “C”.