Owing to the dissentions among the Osage Indians, the main part of this expedition was postponed, however, until the spring of 1805. In a letter bearing the date of July 14, 1804, Jefferson wrote to Dunbar:--"It is very desirable that you make use of any part of the men or matters provided for the expedition and go to what distance, and in what direction you please, return when you please, but in time to report to us the result of your researches, which report will probably induce Congress to enlarge the appropriation."[58] August 18, 1804 he wrote Jefferson that, "in consequence of the permission you are pleased to grant, I have determined to make an excursion up the Washita river and to the hot springs." Two months later, he wrote that he had about completed the necessary preparations for the expedition and that he would carry "several instruments [of his own] in addition to those provided for the party" by the government. Three weeks after writing the above letter, he again wrote to the President from the Post of Washita giving him the latitude of the most important points on the river. After his return to Natchez, he wrote Jefferson the first scientific account of the water at Hot Springs. Subsequent analyses of this water have shown some inaccuracies in this account, but it must be remembered that Dunbar was only a pioneer in this important field. His account reads as follows: "I have examined the water at 130° Fahrenheit under a powerful microscope and found vegetable and animal life, the former a species of moss, the latter a testaceous bivalve of the size of the minutest grain of sand. I do not despair of being able to reanimate these as soon as I can procure a little leisure....[59] From our analysis of the water ... it appears to contain lime with a minute portion of iron dissolved by a small excess of Carbonic acid. This is ... visible upon the first view of the Springs; an immense body of calcareous matter is accumulated upon the side of the hill, by perpetual deposits from the hot waters, and the bed of the run is coloured red oxide of iron or rather Carbonated iron. Every little spring which rises up in a favorable situation forms its own calcareous cup considerably elevated in form of a crater." The following year (1805) Dunbar was given the general supervision of the Red River Expedition. May 24 of that year Mr. Dearborn, the Secretary of War, wrote requesting him to make all arrangements for this expedition, limiting the expenses to $5,000. In a letter bearing the date of March 30, 1807, Mr. Dearborn expressed his appreciation of Mr. Dunbar's services in the following words:--"The frequent drafts on account of the United States upon your time and patience demand an apology, while your disinterestedness and highly useful services entitle you to the most grateful acknowledgements."