The painting depicts Clark at the Great Falls the morning of June 29, 1805 as he prepares to journey out along the river banks and rewrite some notes that had been lost. Clark 'took with him his black man York; Charbonneau and his Indian woman [Sacagawea]'. A torrential downpour hit the group and they sheltered under an overhanging rock in a ravine and were nearly swept away in the ensuing flash flood. Among other items, Clark lost 'an elegant fusee' and a large compass or circumferentor in the flood. He wrote that ' The compass is a serious loss, as we have no other large one'. Returning the next day they were fortunate to recover the circumferentor from the muddy ravine. In the painting Clark is wrapping the circumferentor in a piece of cloth to protect it while in his haversack. The instrument was probably normally stored in a wooden case which would have been awkward to carry while in the field. Surveyors sometimes carried their instruments wrapped this way. The soon to be lost 'elegant fusee' leans against Clark's body.