John H Jackson's parents are given as Edward Jackson and Phoebe Benham and Augusta Blakely's parents as John Blakely and Bathshebe Parks. It is assumed that the mothers were accidentally switched, and that Edward should be Edgar.
This appears to be John Henry Jackson, son of Edgar and Bathsheba Jackson, listed in Hallowell in the 1891 census (with his parents) as a Universalist and also in Hallowell in the 1901 census (with his wife) as a Universalist.