Dunbar rejoined the American Commissioners on August 20. A few days later he made the following entry in his report to the Spanish government:--"I set out on the 31st day of August bidding a final adieu to the Gentlemen of both Commissions, with whom I had spent three months in a manner highly agreeable to my own taste, and with uninterrupted harmony on my part with every gentleman of both parties, and had it not been that my family and other interests demanded my protection and superintendence, I should have with pleasure pursued this employment to its conclusion."[49] Ellicott, in his report of this survey, published in the Transactions of the American Philosophical Society, says:--"To William Dunbar, Esq., of the Mississippi Territory I feel myself under the greatest obligations for his assistance during the short time he was with us; his extensive scientific acquirements, added to a singular facility in making calculations would have reduced my labour to a mere amusement, if he had continued."[50] The same writer in his Journal, published in Philadelphia, five years after his association with Dunbar, says that he is "a gentleman whose extensive information and scientific acquirements would give him a distinguished rank in any place or in any country."[51] Since Ellicott himself was one of the foremost scientists of his time in this country[52] the value of his estimate of Dunbar cannot be questioned. A few months after the completion of this important public survey, Daniel Clarke wrote a letter to Thomas Jefferson, in which he referred to Dunbar as "a person worthy of being consulted____on subjects relating to this Country its productions, or any philosophical Question connected with them____For Science, Probity & general information (he) is the first Character in this part of the World. His long residence in this Country, still but little known to men of letters, its Situation with respect to many Savage tribes, some of which lately inhabited the very Place where he resides & where their visages are still perceptible, the extensive Communications with remote parts presented by the Mississippi and concourse of Indians & traders, have given him many opportunities of making observations which may not have presented themselves to others and may not probably occur in future, to these may be added those he has made on the Country itself, its population, manners, Customs of the Inhabitants, the different Changes in their Government for the last 40 years, the Climate, soil & Trade which are but little known abroad."[53] The manuscript correspondence of Thomas Jefferson, in the Archives of the Department of State at Washington shows that he acted upon this suggestion from Mr Clarke. In this collection there have been preserved fifteen letters that were written by Dunbar.