I have duly recieved your favor of Dec. 15. on the subject of the salt petre rock in your possession, and regret that it is not in my power to serve you with any other information than what follows on that subject. some years ago, Dr Samuel Brown of Kentucky presented to the Philosophical society at Philadelphia a long memoir giving an account of some saltpetre rocks in vast quantity, in some part of Kentucky which yielded an unexampled proportion of the Salt. I do not recollect his process, and he promised further accounts of it, but am uncertain whether he communicated any thing further. I have not the latter volumes of the society, but have no doubt that memoir was printed in them, and that the volume can be furnished you by the printer. I presume you could also learn something on the subject by enquiries from Dr Brown’s friends on the spot, or perhaps from himself now residing at New Orleans. with this scanty information, being all I possess, accept the assurance of my respect

Th: Jefferson