Preheat oven to 375° F.
Combine whole wheat flour and cornmeal in a medium bowl and set aside.
Add soda to buttermilk and allow to stand 5 minutes.
Alternately add buttermilk and molasses to flours, mixing well after each addition.
Bake in a well-greased, 9 by 5 by 2 loaf pan about 40 minutes, or until wooden pick inserted into center of bread comes out clean.