Coleridge wrote the letter to his landscape painter friend Samuel Purkis of Brentford, Middlesex, to ask about acquiring some bhang (a hashish preparation) for an ailing friend, according to the Australian maritime history website Merchant Networks.
He requested that Purkis ask the eminent Sir Joseph Banks — whom Coleridge had heard was in possession of some — for some bhang. Banks advised the government of Great Britain on what best to do to expand British-controlled supplies of hemp.
Coleridge wanted the bhang to treat the intestinal malady of his friend Tom Wedgwood, son of the famous potter Josiah Wedgwood; Sir Joseph Banks knew Josiah. As Banks probably knew, Tom’s health collapsed when he was about 21 — not coincidentally, when he was experimenting with silver nitrates and photography (the younger Wedgwood is credited with being the father of Photography).
The Wedgwoods were well-connected to many 19th century British intellectuals; Emma Wedgwood of the family married evolution theorist Charles Darwin.
The letter to Purkis is Coleridge Letter No. 485, dated February 1, 1803. It is reproduced below:
“I write now to ask a little favor of you. There is a preparation of the Indian Hemp, called Bhang, or àang, or Banghee — the same Drug, which the Malays take, & under it’s influence become most pot-valiant Drawcansirs, run a muck, &c. My friend, T. Wedgewood, is exceedingly desirous to obtain a small specimen of it: from what he has heard of it, he conceives it possible that it may afford some alleviation to his most hopeless malady — which is a dreadful inirritability of the intestinal Canal. Now I know that Sir Joseph Banks has a quantity of it — and if you should see him sḥortly, & could procure a small quantity of it — (you may mention, if you choose, for whom you want it — & Sir Joseph was an intimate”