Cream butter and sugar; add egg and beat well. Add vanilla and molasses. Add sifted dry ingredients alternately with milk. Dredge the blueberries with a little flour (this keeps them from sinking to the bottom of the cake). Add the dredged blueberries and fold in gently. Bake 1 1/2 hours at 350 degrees in two loaf pans or a large pan filled about 2/3 full. May take longer for the larger cake. Cake is baked when skewer inserted into the centre comes out clean.