Sir, - A correspondent in your paper (December 15th) correctly urged people anxious to air their opinions about Roger Casement to get their facts right. There was such confusion in the public mind about various maritime incidents concerned with the 1916 Rising in the early days of the State that, when preparations were being made to celebrate the jubilee of the Rising, the Maritime Institute undertook to research the incidents in question and publish the facts as they were revealed. The result was the appearance in April 1966 of the Institute's book The Sea and the Easter Rising, a review of the third edition of which, published this year, recently appeared in your paper. Copies are available from the National Maritime Museum, Haigh Terrace, Dun Laoghaire at £3.95, post about 60p.The ship that brought rebel arms but not Casement, and failed to rendezvous at midnight on the Thursday before the Rising with the German submarine U19, in which Casement was travelling, was not the Aud but the German auxilliary warship, the ex-Wilson Line steamer SMS Libau, carefully disguised to represent the Aud, which was a Norwegian cargo ship that was at that time loading cargo at a port in Southern Spain.A careful search revealed that the commander of the U19, Kapitan Zur-See Raimund Weisbach, was still alive in 1966. He was invited to the jubilee celebrations and the press photograph of the year appeared in The Irish Times, taken by your photographer Gordon Standing, or Weisbach walking alone at sunrise along Banna Strand, on which Casement was disembarked from U19 50 years before, having waited in vain for Libau to appear: her commander had in fact lost his way, and was at the mouth of the Shannon. Photographs of U19's voyage and her track chart, as well as gifts from Weisbach, are on view in the Maritime Museum. - Yours etc.,John de Courcy Ireland,Honorary Research Officer,Maritime Institute of Ireland,Haigh Terrace,Dun Laoghaire.