January 15, 1805
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Aug 30, 1803 Sep 30, 1806

January 15, 1805


between 12 & 3 oClock this morning we had a total eclips of the moon, a part of the observations necessary for our purpose in this eclips we got which is at 12h 57m 54s    Total Darkness of the moon    @ 1 44 00    End of total Darkness of This moon    @ 2 39 10    End of the eclips— [1]

This morning not So Cold as yesterday    wind from the S. E.    wind choped around to the N W.    Still temperate    four Considerate men of the Minetarre Came to See us    we Smoked in the pipe, maney mands. [Mandans] present also, we Showed [NB: attentions] to those men who had been impressed with an unfavourable oppinion of us. [NB: which satisfied them]


Observed equal Altitudes of the ☉ with sextant and Glass artifical horizon adjusted with a sperit level

  h m s     h m s
A. M. 8 26 32       P. M.
  " 29 14    
  " 32   1      1 49 46

Altitude given by the sextant at the time of obtn.    26° 6' 15"

  h m   s
Chronomerter too slow on mean time— 1 1 57.7

Chronometer's daily rate of going, as deduced from this observation, and that of the 22nd of December 1804 is too slow on mean time    s 55.8

☞ I do not place much confidence in this observation in consequence of loosing the observation of the Altitude of the ☉'s L. L. and center P. M. and that his U. L. was somewhat obscured by a cloud.    the weather was so could that I could not use water as the reflecting surface, and I was obliged to remove my glass horizon from it's first adjustment lest the savages should pilfer it.


Tuesday 15th Jany.    a warm pleasant day. Shannon Sent with the horses down to the hunters.    about 2 oClock Several of the Grovantares chiefs came to See us.    the weather is thoughy [thawing] So that the Snow melts off the huts &.C.


Tuesday 15th Jany. 1805.    warm to what it has been.    the man who went to the fort yesterday, Came down with 2 horses after me & Some meat, the day kept warm & pleasant.—

Tuesday January 15th    This day the weather had moderated considerable, the Man who arrived Yesterday at the Fort, was sent down with 2 horses (which was procured from the Mandan Village) after the Man that was frost bitten, and to bring up some Meat from the Hunters.—

1. The captains discussed their observations with Larocque on January 30. As he recalled it, they asserted that David Thompson had placed the Mandan and Hidatsa villages much too far west on his 1798 map, and that they had now corrected this by their observations of the eclipse. In fact, Thompson's longitude for the villages (101° 14' 24" W. for Matootonha) is relatively close to the actual position (101° 27' W.). The captains' observation from the eclipse gave a position about two degrees east of the true one (99° 26' 45" W.). However, Lewis actually did not place too much confidence in some of these observations, because of the slowness of the chronometer and meteorological difficulties. On Clark's Fort Mandan map (Atlas maps 32a, 32b, and 32c), the villages appear west of 101° W. longitude. Since the captains had a version of Thompson's map, they may have abandoned their own observations, in which they had less confidence than Larocque suggests, and followed Thompson. Larocque may have misunderstood what he was told. Wood & Thiessen, 151–52; Allen, 87–93, 117 n. 19, 142, 162; Thompson, 179; Nicholas Biddle to John Vaughn, [ca. October 13, 1810], Jackson (LLC), 2:560–61; Diller (MMR), 517–18. (back)
2. Lewis's astronomical observation from Codex O. (back)