1To Thomas Jefferson from Thomas S. A. Matthews, 20 September 1823 (Jefferson Papers)
I would very gladly have your opinion on a subject which I shall lay before you, though I have been almost afraid that on account of your great age and bodily infirmity you would scarcely take it upon yourself to give me an answer.— The question on which I wish your opinion is whether a Chronometer which will keep time with the sun on every day in the year will be valuable or not. It is so...