I checked the index for Hamburg, German passenger departures that is on-line and found the following two entries:
Wilhelm Kadow, age 48, passenger #523567, departed Hamburg for SANTOS in 1895.
Wilh. (Wilhelm) Kadow, age 50, passenger #519748, departed Hamburg for SANTOS in 1897.
It would appear that Wilhelm Kadow left Germany in 1895 for Brazil, returned to Germany, then returned in 1897. The on-line index only begins in 1890, so if your great-grandfather came over in 1889 or earlier, those records are available only on microfilm.
Is Wilhelm Kadow your great-grandfather? I can help you with your genealogy, if you'd like. I have 20 years experience with reading German genealogical documents including the old German script which is very difficult for novices.
If you would like assistance with your genealogy, please let me know. I could find the village in Germany that your family comes from. My Christopher ancestors come from Pommern, as well. Please let me know if I can help you. You could also help me because I am currently unemployed with a hip/back injury.
San Diego, California