Dissolve yeast in two cups lukewarm water in large mixing bowl.
Add salt and sugar and mix well. With wooden spoon, beat in enough flour, 1 cup at a time, to form a smooth ball that clears side of bowl. Cover, and set in warm place free from drafts, for one and a half hours, or until doubled in bulk.
Stir down, then turn out on lightly floured board. Knead a few turns, then cut in half. Shape each half in a loaf, about 12 inches long. Put on baking sheet, well sprinkled with cornmeal.
Let rise 5 minutes, then slash tops in 4 places with sharp knife. Brush with water and put in cold oven with pan of boiling water on bottom rack.
Turn oven control to 400 degrees F, and bake 40 minutes, or until crusty and lightly browned. Best served hot.