Are you certain it's Thomas Muir and not Robert ?

Brian Lawson's dissenting baptisms show a couple of children to Robert Muir and Ann Kermode registerred at the Scotch Church.

This church is the presbyterian church of england, called St Andrews and more detail can be found in Manx Notebook.

The ship J Z has the following amongst its passengers arriving at New York 26 Aug 1848 :-

Robert Muir 41
Ann 30
Thomas 12
Sarah 4
Edward 2
John 1
Elizabeth infant

I wonder if this list is the family .

Len Faragher