There's a Hosea Ballou title at the Gutenberg Project, the decade plus old resource for plain text public domain works. (Yours truly was the first to add a Unitarian text to Gutenberg Project, Channing's Unitarian Christianity. Those were in the Gopher days. Very old school. Hold your applause.)
That's why I'd like to thank
Produced by David Starner, David King and the Online Distributed
Proofreading Team from a book given for scanning by
Rev. Felicia Urbanski.
for getting A Series of Letters in Defence of Divine Revelation online this month.