A 36-foot leather-hulled boat is crawling across the northern edge of the Atlantic shipping lanes in an attempt to prove ancient legends that Irish monks beat Columbus to North America by 900 years and the Vikings by 500.

Named the Brendan after St. Brendan, a 6th-century seafaring Irish monk, the vessel with its skipper and four-man crew last week reported a position within 650 miles of the Newfoundland coast, according to the National Geographic Society, supporting the voyage with Reader's Digest Press.

Headed by Oxford Scholar and historian Timothy Severin, 36, the expedition left Ireland in May 1976, stopping over in the Faeroes islands before proceeding on to Iceland where it arrived by early July. Forced to lay over there for the winter, the voyage was resumed last month. Once its signal is picked up by Newfoundland radio operators, a chartered plane and ship will track it to shore.

Its namesake, St. Brendan, was the hero of "Navigatio Sancti Brendani Abbatis," an account of his meanderings with 17 shipmates that lasted seven years. Sometimes called the world's first best seller, it told of St. Brendan discovering exotic or spectacular lands which historians today find not dissimilar to places like the Azores, Newfoundland and Florida.

The Brendan resembles the Irish "curraghs" which Irish sailors still row and sail off the Irish coast today. Built of light wood, the Brendan is covered with the hides of 25 oxen and waterproofed with a concoction of tallow and cod oil that Roman sailors supposedly used when they sailed the waters off Ireland.

Besides historical compliance with nautical detail, the Brendan carries the latest navigational and communications equipment, foul-weather gear and scientifically-designed rations. The vessel withstood Force 9 winds in the first leg of its voyage between Ireland and Iceland last year, but this year equally strong winds prevailed and set it wangering in circles for several days shortly after departing Iceland.

Norse sagas refer to earlier Celtic explorations of the New World but proof of these adventures remains elusive. Books like St. Brendan's describe in fanciful terms sites that could have been part of the New World, say some historians. The Brendan's skipper and crew hope to show through painstaking attention to detail that St. Brendan could, indeed, have gotten here first.