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.
3rd--An Artificial Horizon on the construction recommended and practiced by Mr. Andrw. Ellicott of Lancaster, Pensyla., in which water is used as the reflecting surface; believing this artificial Horizon liable to less error than any other in my possession, I have uniformly used it when the object observed was sufficiently bright to reflect a distinct immage; but as much light is lost by reflection from water I found it inconvenient in most cases to take the altitude of the moon with this horizon, and that of a star impracticable with any degree of accuracy.
4th--An Artificial Horizon constructed in the manner recommended by Mr. Patterson of Philadelphia; glass is here used as the reflecting surface. this horizon consists of a glass plane with a single reflecting surface, cemented to the flat side of the larger segment of a wooden ball; adjusted by means of a sperit-level and a triangular stand with a triangular mortice cut through it's center sufficiently large to admit of the wooden ball partially; the stand rests on three screws inserted near it's angles, which serve as feet for it to rest on while they assist also in the adjustment. this horizon I have employed in taking the altitude of the sun when his image he has been reather too dull for a perfect reflection from water; I have used it generally in taking the altitude of the moon, and in some cases of the stars also; it gives the moon's image very perfectly, and when carefully adjusted I consider it as liable to but little error.
5th--An Artificial Horizon formed of the index specula of a Sextant cemented to a flat board; adjusted by means of a sperit level and the triangular stand before discribed. as this glass reflects from both surfaces it gives the images of all objects much more bright than either of the other horizons; I have therefore most generally employed it in observing the altitudes of stars
6th--A Chronometer; her ballance-wheel and escapement were on the most improved construction. she rested on her back, in a small case prepared for her, suspended by an universal joint. she was carefully wound up every day at twelve oclock. Her rate of going as asscertained by a series of observations made by myself for that purpose was found to be 15 Seconds and a 5 tenths of a second too slow in twenty four howers on Mean Solar time. This is nearly the same result as that found by Mr. Andrew Ellicott who was so obliging as to examine her rate of going for the space of fourteen days, in the summer 1803. her rate of going as ascertained by that gentleman was 15.6 s too slow M. T. in 24 h. and that she went from 3 to 4 s. slower the last 12 h, than she did the first 12 h. after being wound up.
at 12 OCk. on the 14th day of may 1804 (being the day on which the detachment left the mouth of the River Dubois) the Chronometer was too fast M. T. 6 m. 32 s. & 2/10.--This time-piece was regulated on meantime, and the time entered in the following observations is that shewn by her at the place of observation. the day is recconed on Civil time, (i e) commencing at midnight.
7th--A Circumferentor, circle 6 Inches diameter, on the common construction; by means of this instrument adjusted with the sperit level, I have taken the magnetic azimuth of the sun and pole Star. It has also been employed in taking the traverse of the river:--from the courses thus obtained, together with the distances estimated from point to point, the chart of the Missouri has been formed which now accompanys these observations. the several points of observation are marked with a cross of red ink, and numbered in such manner as to correspond with the celestial observations made at those points respectively.
[Clark, July 23, 1804] Camp 10 Ms. above the river Plate Monday July the 23rd a fair morning--Sent out a party of 5 men to look to timber for Ores two other parties to hunt at 11 oClock Sent, G. Drewyer & Peter Crusett 1/2 Indn. to the Otteaus Village about 18 ms. West of our Camp, to invite the Chiefs & principal men of that nation to come & talk with us &. &., also the panic if they Should meet with any of that nation (also on the S. Side of the Plate 30 ms. higher up) (at this Season of the year all the Indians in this quater are in the Plains hunting the Buffalow from Some Signs Seen by our hunter and the Praries being on fire in the derection of the Village induce a belief that the Nation have returned to get green Corn) raised a flag Staff put out Some provisions which got wet in the french Perogue to Sun & Dry--I commenced Coppying my map of the river to Send to the Presdt. of U S. by the Return of a pty of Soldiers, from Illinois five Deer Killed--one man a bad riseing on his left breast. Wind from the N. W.
[Clark, July 23, 1804] Camp White Catfish 10 Miles above the Platt River Monday the 23rd of July 1804 A fair morning Set a party to look for timber for Ores, two parties to hunt. at 11 oClock Sent off George Drewyer & Peter Crousett with Some tobacco to invite the Otteaus if at their town and Panies if they Saw them to Come and talk with us at our Camp &c. &c. (at this Season the Indians on this river are in the Praries Hunting the Buffalow but from Some Signs of hunters near this place & the Plains being on fire near their towns induce a belief that they this nation have returned to get Some Green Corn or rosting Ears) raised a flag Staff Sund & Dryed our provisions &c. I commence Coppying a map of the river below to Send to the P. ____ U S five Deer Killed to day one man with a turner on his breast, Prepared our Camp the men put their arms in order
Wind hard this afternoon from the N. W.
Equal altitudes taken at the White Catfish Camp, 10 miles above the river Platt-
[Clark, July 24, 1804] White Catfish Camp 24th of July Tuesday. a fair morning the wind rose with the Sun & blows hard from the S. thos Southerley Breezes are dry Cool & refreshing. the Northerley Breezes which is more frequent is much Cooler, and moist, I continue my Drawing. Cap Lewis also ingaged prepareing Som paper to Send back, one of the men cought a white Catfish, the eyes Small, & Tale resembling that of a Dolfin.
[Clark, July 24, 1804] White Catfish Camp 10 Ms. above Platt 24th, of July 1804 Tuesday a fair day the wind blows hard from the South, the Breezes which are verry frequent on this part of the Missouri is cool and refreshing. Several hunters out to day; but as the game of all Kinds are Scarce only two Deer were brought in--I am much engaged drawing off a map, Capt. Lewis also much engaged in prepareing Papers to Send back by a pirogue--Which we intended to Send back from the river Plate--observations at this place makes the Lattitude 41° 3' 19" North