This is great with baked beans and franks. It's dark and dense, and leftovers make wonderful toast.
In a large bowl, combine the whole wheat and rye flour, cornmeal, baking soda, and salt. Make a well in the center and pour in the molasses, buttermilk, and raisins. Stir until all the ingredients are combined.
Grease a 2 quart mold, flour it, and fill. The batter should not fill more than 2/3 of the mold. Cover with foil and tie with string. Set the mold on a trivet in the bottom of the slow cooker. Pour the hot water into the pot, cover the pot, and cook on High for 3 to 4 hours.
The bread is done when the top is dry and recedes from the edge of the mold. Cool the bread on a rack for 10 minutes, then turn out and serve.
Makes 1 loaf.