Copy letter from Robert William Frederick Harrison, to Professor Silvanus Thompson, Fellow of the Royal Society 'Dear Sir, I am directed to ask if you will be good enough to undertake to write an Obituary Notice of Dr Sprengel, whose death was reported to the President and Council at their meeting on Thursday last. I am, Dear Sir, faithfully yours, Robt [Robert] Harrison Asst. Sec. R.S. [Assistant Secretary, Royal Society]'. 20 January 1906