Dissolve yeast in warm water in a large mixing bowl; stir well. Add butter and 1 tablespoon salt, stirring until butter melts. Cover and let stand 5 minutes. Stir in 6 1/2 cups flour to form a stiff dough.
Turn dough out onto a surface sprinkled with remaining flour; knead 8 minutes or until dough is smooth and elastic. Place dough in a greased bowl, turning to grease top. Cover and let rise in a warm place (85°), free from drafts, 1 1/2 hours or until doubled in bulk. Punch dough down, and turn out onto a lightly floured surface. Cover and let rest 15 minutes.
Divide dough into thirds; roll each portion into a 13- x 7-inch rectangle. Roll up each rectangle jellyroll fashion, starting at long end. Pinch seams and ends together to seal. Sprinkle 3 heavily- greased baguette pans or baking sheets with cornmeal. Place loaves, seam side down, in baguette pans or on baking sheets.
Cut 3 or 4 diagonal slashes, 3/4-inch deep, in top of each loaf. Cover; repeat rising procedure 40 minutes or until doubled in bulk. Combine egg white and 1 teaspoon salt; mix well. Brush on loaves.
Bake at 425° for 30 minutes or until loaves sound hollow when tapped. Remove bread from pans or baking sheets immediately; cool on wire racks.