Sour Dough French Bread

In large bowl soften yeast in 1 1/2 cups warm water. Blend in 2 cups of the flour sour dough starter, sugar, butter and 2 teaspoons salt. Combine 1 cup flour and soda; stir into flour-yeast mixture. Add enough remaining flour to make a moderately stiff dough. Knead 5 to 8 minutes. Place in greased bowl, turn once. Cover, let rise until double. Punch down. Divide in half. Cover, let rest 10 minutes. Shape in 2 oblong or round loaves. Place on greased baking sheet sprinkled with cornmeal. Cover; let rise until almost double. Brush with water and make diagonal slashes across top. Bake at 375 degrees for 30 to 35 minutes.