However, Markham had second thoughts, and was soon writing to the current RGS president, Leonard Darwin, to express disbelief about Shackleton's claimed latitudes, repeating these doubts to Scott. Historians have surmised that Scott was Markham's protégé, and that the old man resented polar glory going to someone else. Whatever his reason, Markham adopted a bitterness towards Shackleton which he retained for the rest of his life. He is said to have crossed out all favourable references to Shackleton in his own notes on the "Discovery" expedition, and to have virtually ignored Shackleton's achievements in a 1912 address to the British Association. He was equally dismissive in his history of Antarctic exploration, "The Lands of Silence" – published posthumously in 1921).