July 22, 1804
July 22nd Sunday Set out verry early with a view of getting Some
timbered land & a good Situation to take equil altitudes in time
proceeded on nearly a North 15° W 7 ms. to a pt. S. S. opposit Some high
Lands on L. S. above the upper point of a long willow Island in the
middle of the river 6 Deer killed to Day we deturmined to Stay here 4
or 5 days to take & make obsvts. & refresh our men also to Send
Despatches back to govement— Wind hard N. W. Cold
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.
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
July 22nd
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.
