Soak ears of corn in salt water for 1/2 to 1 hour without disturbing the husks. Remove from water; shake off excess. Place on the grill, 4 or 5 inches above the coals (or the ears can be placed directly in the ashes of a moderate fire); turn occasionally. When husks have turned light brown on all sides, corn is ready. Pull back husks; the silk comes off with the husks. Serve with butter and salt.