Darwin to Matthew, 15 March 1871. Letter 7585: Darwin Correspondence Project
Note that the text of this letter is not currently available from the Darwin Correspondence Project (as of Sept 2014). However, the text is available from pp.42-43 of De Beer, Gavin, ed. (1959). Some unpublished letters of Charles Darwin. Notes and Records of the Royal Society of London 14: 12–66, and is reproduced below.
In this reply to Matthew’s letter of 12 March, punctually produced three days later, Darwin compliments Matthew on the “pristine vigour” of his views, and contrasts this with his own ailing health.
Down, Beckenham, Kent
I thank you for your kind letter. You show no signs of your four score years in your letter or in the newspaper article, which seem written with your pristine vigour. -My health keeps very indifferent and every exertion fatigues me, so that I doubt whether I shall be good for much more. Your parable of the Damascus Woman is quite new to me and very striking.
I sincerely wish you a happy meeting with your son.-I have many letters to write so pray excuse my brevity, and believe me,