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.