Halvord Kristensen

I am looking for the name of the ship which Halvord, his wife Birte Thorgeirsdatter and their children Kristian, Marie, Jørgen and Hanna rode when they emigrated. Information provided to me indicates they left Oslo 26 august 1870, but I can find no record of it. Supposedly their final destination was Milwaukee, Wisconsin, but I don't know if they came through New York or Quebec. Other information I have is that they're listed on the 1865 Census, Municipality: Skoger, Municipality number: 0712, Name of domicile: Unelsrød, Number of persons in this domicile: 9. So in 1870 Halvord would have been about 68 years old (b. 1812) and Birte would have been 59 years old (b. 1821) and their children's ages would have ranged from 32 to 3 years old. Any help in this matter would be greatly appreciated. John