22nd of July 1804 Completlly arranged our Camp, posted two Sentinals So as to Completely guard the Camp, formd bowers for the min $cc. &. Course from R Plate N 15° W. 10 Ms.
[Clark, July 22, 1804]
July 22nd, Sunday 1804 Set out verry early with a view of Getting to Some Situation above in time to take equal altitudes and take Observations, as well as one Calculated to make our party Comfortabl in a Situation where they Could recive the benifit of a Shade—passed a large Sand bar opposit a Small river on the L. S. at 3 miles above Plate Called Papillion or Butterfly Creek a Sand bar & an Willow Island opposit a Creek 9 ms. above the Plate on the S. S. Called Mosquitos Creek Prarie on both Sides of the river. Came too and formed a Camp on the S. S. above a Small Willow Island, and opposit the first Hill which aproach the river on the L. S. and covered with timbers of Oake Walnut Elm &c. &. This being a good Situation and much nearer the Otteaus town than the Mouth of the Platt, we concluded to delay at this place a fiew days and Send for Some of the Chiefs of that nation to let them Know of the Change of Government, The wishes of our Government to Cultivate friendship with them, the Objects of our journy and to present them with a flag and Some Small presents
Some of our Provisions in the French Perogue being wet it became necessary to Dry them a fiew days—Wind hard from N W. five Deer Killed to day—The river rise a little
[Lewis, July 22, 1804]
July 22nd 1804. A summary discription of the apparatus employed in the following observations; containing also some remarks on the manner in which they have been employed, and the method observed in recording the observations made with them.
1st—a brass Sextant of 10 Inches radius, graduated to 15 which by the assistance of the nonius was devisible to 15"; and half of this sum by means of the micrometer could readily be distinguished, therefore-7.5" of an angle was perceptible with this instrument; she was also furnished with three eye-pieces, consisting of a hollow tube and two telescopes one of which last reversed the images of observed objects. finding on experiment that the reversing telescope when employed as the eye-piece gave me a more full and perfect image than either of the others, I have most generally imployed it in all the observations made with this instrument; when thus prepared I found from a series of observations that the quantity of her index error was 8' 45"-; this sum is therefore considered as the standing error of the instrument unless otherwise expressly mentioned. the altitudes of all objects, observed as well with this instrument as with the Octant were by means of a reflecting surface; and those stated to have been taken with the sextant are the degrees, minutes, &c shewn by the graduated limb of the instrument at the time of observation and are of course the double altitudes of the objects observed.
2ed—A common Octant of 14 Inches radius, graduated to 20', which by means of the nonius was devisbile to 1', half of this sum, or 30" was perceptible by means of a micrometer. this instrument was prepared for both the fore and back observation; her error in the fore observation is 2°+, & and in the back observtion 2° r 1' 40.3" + at the time of our departure from the River Dubois untill the present moment, the sun's altitude at noon has been too great to be reached with my sextant, for this purpose I have therefore employed the Octant by the back observation. the degrees ' & ", recorded for the sun's altitude by the back observation express only the angle given by the graduated limb of the instrument at the time of observation, and are the complyment of the double Altitude of the sun's observed limb; if therefore the angle recorded be taken from 180° the remainder will be the double altitude of the observed object, or that which would be given by the fore observation with a reflecting surface.