The Journals of Lewis & Clark: Lewis, July 21, 1804

Updated May 14, 2020 | Infoplease Staff

Lewis, July 21, 1804

July 21, 1804

by a boiling motion or ebolition of it's waters occasioned no doubt by the roling and irregular motion of the sand of which its bed is entirely composed. the particles of this sand being remarkably small and light it is easily boied up and is hurried by this impetuous torrent in large masses from place to place in with irristable forse, collecting and forming sandbars in the course of a few hours which as suddingly disapated to form others and give place perhaps to the deepest channel of the river. where it enters the Missouri it's superior force changes and directs the courant of that river against it's northern bank where it is compressed within a channel less than one third of the width it had just before occupyed. it dose not furnish the missouri with it's colouring matter as has been asserted by some, but it throws into it immence quantities of sand and gives a celerity to it's courant of which it abates but little untill it's junction with the Mississippy. the water of this river is turbid at all seasons of the year but is by no means as much so as that of the Missourie. The sediment it deposits, consists of very fine particles of white sand while that of the Missoury is composed principally of a dark rich loam-in much greater quantity

21st July from the experiments and observations we were enabled to make with rispect to the comparative velocities of the courants of the rivers Mississippi Missouri and Plat it results that a vessel will float in the Mississippi below the entrance of the Missouri at the rate of four miles an hour. in the Missouri from it's junction with the Mississsippi to the entrance of the Osage river from 51/2 to 6 from thence to the mouth of the Kanzas from 61/2 to 7. from thence to the Platte 51/2 while the Plat is at least 8.- The Missouri above the junction of the river plat is equal to about 31/2 miles an hour as far as the mouth of the Chyenne where its courant still abates and becomes equal to about three miles an hour from information it dose not increase it's volocity for