The Historical Committee met last night, when your Letter of the 30th ulto & my answers of the 5th & 6th inst. were laid before them. They have ordered me to reiterate to you the thanks which I had already anticipated for the many favors which they have received at your hands, & particularly for the Communications accompanying your last. Your Memoir on the boundaries of Louisiana was read, & the Committee did not See without astonishment the whole ground of Argument covered by a Simple but luminous statement of facts, made at a time when the Subject was entirely new, & before the least track had been made in that until then untrodden field. I assure you, Sir, that our Committee duly appreciates your valuable Communications. You would be pleased to see the Zeal which you have excited for the advancement of Literature & science. I have no doubt that it will in time produce good fruits; & thus in your retirement you will have contributed to the lasting honor of your Country.

The Volume of Transactions of the Society now in the press will be out in about three Weeks—The Historical Committee have materials on hand for Several Volumes of their own Separate Transactions, & contemplate publishing the first in the Course of the ensuing Summer.

The Vocabularies which you have been So good as to communicate to us, have already ascertained an interesting fact respecting Indian Philology. The late Dr Barton in his New Views Appendix, page 5. had asserted that the language of the Nanticokes, was an idiom Sui generis, & bore no resemblance or analogy to the Delaware. From the geographical situation of the Nanticoke tribe, I had always believed, notwithstanding Dr Barton’s assertion, that the Nanticoke was like the Delaware, a Dialect of the Algonquin, & I have had the satisfaction to be fully convinced of it by your Nanticoke Vocabulary & another furnished to us by Mr Heckewelder of Bethlehem, which agrees with yours. Indeed, in all the Country which lies between the Atlantic, the st Lawrence & the Lakes, the Mississipi & the Southern boundary of Virginia, I have not been yet able to discover traces of an Indian language that is not a Dialect either of the Algonquin or Iroquois, & the Dialects of the former are by far the most Numerous. South of Virginia, & perhaps of North Carolina, other Dialects commence, Such as the Creek, Cherokee &c, not connected in appearance either with the Iroquois or Algonquin. Your Vocabularies will enable the Committee with such further lights as they may obtain by a Correspondence with Indian Agents to pursue their enquiries further, & to trace the Grammatical forms as well as the words of those languages.

I am very Sorry to inform you that Dr Wistar lies very ill of the Typhus fever, combined with a pectoral affection. This is the eighth day since his attack; the Physicians expected a Crisis Yesterday which did not take place. Yet his Case is not considered desperate. But the greatest anxiety is felt for him. The Committee went last night in a body to enquire after his health. If we Should lose him, it will be a general misfortune.