RC (DLC); at foot of text: “Thomas Jefferson President of the U. States”; endorsed by TJ as received 30 Aug. and so recorded in SJL. Enclosure: Marqués de Casa Calvo to Claiborne, 15 July; persuaded of the scientific nature of the proposed Red River expedition, Casa Calvo accedes to Claiborne’s request and will issue a passport to William Dunbar whenever necessary; because the river runs into the province of Texas and possibly into a more internal province, Casa Calvo will inform other Spanish authorities of the plan (Tr in same, in Spanish; translation printed in Rowland, Claiborne Letter Books description begins Dunbar Rowland, ed., The Official Letter Books of W. C. C. Claiborne, 1801–1816, Jackson, Miss., 1917, 6 vols. description ends , 3:128-9).