Can tell you that a William Nixon Chapman married a Louisa Theresa Moore in 1863 and also an Eliza Pascoe in 1875. Might be the same groom in each case. There is also a 1901 marriage between Mary Crombie Wilson and a William Nixon Chapman. Christchurch Archives hold a probate for a William Nixon Chapman dated 1876 but he is not mentioned in the Christchurch City Cemeteries Database. http://www.archway.archives.govt.nz/Home.do
HiNot sure if you are still looking for info on William Nixon CHAPMAN. I am descended from his sister Ann Matilda Chapman. William committee suicide in 1876 by throwing himself of the boat he was captaining.I'm happy to give more information if you are still looking.Rachel