Letter from Commander Ernest Henry Shackleton, Antarctic Expedition 1907, 9 Regent Street, Waterloo Place, London, to Robert [William Frederick] Harrison, Assistant Secretary of the Royal Society, Burlington House 'Dear Sir, I beg to acknowledge receipt of the spare proof copy of the "Discovery's" Magnetic Observations; I am greatly obliged for this. I am, Dear Sir, Yours faithfully, E H Shackleton'. 9 October 1907