Internet Archive has a 1961 edition, and it's mirrored on 4nn4's Archive.
https://archive.org/details/principlesofelec0000unse_a3j0
(AA can be searched using an archive.org file slug, e.g. "principles...a3j0", or obviously by using the title)
https://archive.org/details/principlesofelec0000unse_a3j0
(AA can be searched using an archive.org file slug, e.g. "principles...a3j0", or obviously by using the title)