To clarify the 1850 Bangor, Maine census:
James Martin, 38, (cannot read occupation), Scotland
Janet Martin, 15, Scotland
Rachael(?) Martin, 13, Scotland
Nathan(?) Martin, 13, Scotland
James Martin, 10, England
Mary Martin, 7, England
Wm(?) Martin, 24, Scotland
James Smith, 20, Scotland
I cannot read the three adults' occupations, but they are all the same. It could possibly be Clerk?
Have you found this family in England in 1841?