'It occurred to me; much about the same time that it would be proper to study Stewart's Essays, Berkel[e]y's principes of knowledge, Rumfords Essays, Newton ['s] Institutes, Simpson's Fluxions &c &c - If to these overpowering engagements you add the numberless fits of indolence - and the perpetual visitations of spleen, to which one is subjected in this dirty little uncomfortable planet of ours - I presume you will have a sufficient excuse for my silence; and will rather wonder indeed that you have heard from me at all.'