Weems & Plath Nautical Slide Rule. #105. So simple a child can operate it. Gives immediate solution to all speed-time-distance problems. Equally applicable for nautical or statute miles. Speed in knots or MPH. Time in hours, minutes, or seconds. Distance is in nautical or statute miles (or yards if desired and if speed is in knots. ) Easy to read and accurate. Standard in U. S. Navy.