Book digitized by Google and uploaded to the Internet Archive by user tpb.
"From the third London edition."
The original 7 letters were written in 1846, and published in Frankfurt a.M. under title Letters on the truths contained in popular superstitions. They and the added 7 letters were published in the 3rd expanded ed. in 1851, under title On the truths contained in popular superstitions, with an account of mesmerism