Fourth-graders at Edgewood School in Scarsdale had the opportunity to learn about latitude and longitude, the fierceness of the world's oceans, and the workings of huge ocean liners during a recent visit and presentation by Captain Ian T. Blackley, president and CEO of Overseas Shipholding Group . Blackley, who is married to Edgewood teacher Marilyn Blackley, worked at sea for 20 years, serving as captain for the Peninsular and Oriental Steam Navigation Company from 1987 to 1991.