Another child of John & Martha is a Sophie McCormack, born about 1874. In an outgoing passenger record, I find a Sarah McCormack, aged 28, and Sophie, aged 19, leaving Londonderry in 1893. Perhaps Sarah is older than we think?
The matching incoming record for the ship into New York has them bound for South Manchester so perhaps we have identified the right family. Need to find marriage records to determine if we are correct.
Believe I have found Sophia in the 1900 census married to a Joseph Stevenson in Manchester.