Six letters to a pious man, introduced by an address to Bishop Hughes : Heinzen, Karl, 1809-1880 : Free Download, Borrow, and Streaming : Internet Archive
archive.org
Avery Classics copy: Bound with A Guide to the Central park and no.3 and no. 5 of Anti-Slavery tracts

The author is a “48er”, one of the people in Germany who were exiled after the Revolutions of 1848. There’s some really interesting stuff here.