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Thanks to Andrew Corl for an interesting contribution about American
timekeeping in the early 1800s. It's good to make contact with anyone
interested in L&C's navigation.

He writes-

>Lewis never makes mention of a
>clock or pocket watch on the trip.  If he or Clark had them they would
>probably have left them with friends or family, as watches would have
>been passed down from one generation to another.


and, later-
>One item that interested me, when I looked
>at the list of supplies, was the lack of a naval chronometer.

They certainly carried a chronometer, as described on page 412 of vol 2 of
Moulton's Journal, in the list of the navigational equipment that the
expedition carried, as-

"A chronometer; her balance wheel and [e]scapement were on the most
improved construction. She rested on her back, in a small case prepared for
her, suspended by a universal joint..."

They recorded times of events in a way that would have been quite
impossible without a seconds-hand.

The chronometer lost time at a rate of 15.5 seconds per day right from the
start of the journey, which would have been quite acceptable if that rate
had stayed constant. But later, the rate varied considerably, and at times
the instrument stopped altogether.

As a result, and also as a result of their travel over a great span of
longitude, the chronometer would depart (by hours) from local apparent
time. Although they must have had in mind a good idea of what this
departure was, from day to day, it would have been useful to have an
ordinary watch on board, with or without a seconds-hand, and set to local
apparent time, for the simple purpose of telling the apparent time of day
without having to do arithmetic.

For example, they often note in the journal the time in the morning they
cast-off from the bank and started travelling. And they would need to
forecast the approach of apparent noon, so as to put-ashore for a meridian
Sun sight. I haven't found a mention of any such auxiliary timekeeper, but
as yet have only briefly scanned the journals for the early legs of the
journey. It seems unlikely that one was carried, because if it was, it
would have been most useful for resetting the chronometer after it stopped,
and would surely have deserved a mention at that point.

>I also
>have looked at the journals of Lewis and Clark and it is recorded that
>Lewis was requested to simply take observations that the corresponding
>calculations would be performed later.

There's an interesting paper about this by the late Richard.S.Preston, "The
accuracy of the Astronomical Observations of Lewis and Clark", available
at-


>I read into this that Lewis had
>a difficult time with the calculations of latitude and longitude


Calculating the longitudes may have been beyond him, but he should have
been able to cope with simple latitude calculations. However, he made many
elementary errors, as I keep discovering. One, which was pointed out by
Rudner & Heynau, was a failure to allow correctly for sextant index error
when reading the doubled altitudes that an artificial horizon produces. The
index error should be corrected, and then the result halved, but L&C, in
error, did these the wrong way round (throughout the voyage, it seems). As
a result, EVERY reflected altitude was in error! See "We Proceeded On", vol
27 no 4 (Nov 2001), which contains interesting papers about the L&C
celestial navigation

Although L&C were given some comprehensive instructions on celestial nav.,
to take with them to supplement Lewis' "crash course", they did not explain
how to process sights taken with an artificial horizon. Those instructions
were provided by the astronomer Robert M Patterson; a transcript is
available at .

>also
>the necessity of taking several volumes of books to assist with the
>calculations may have been more weight then he wanted on the trip.

Volumes of the Nautical Almanac were taken with them (not sure how many
years ahead) which would provide all the astronomical data they would need,
for lunars as well as for latitudes. And they did made an attempt to work a
lunar, so must have had the necessary log tables with them anyway. I
haven't yet got anywhere near the later stages of their outward journey,
when weight must have became more critical.

To me, it looks more and more as though Lewis was accurate with his
sextant, and produced many good observations, but had a tendency to make
many elementary errors, and didn't really understand the basics of what he
was doing. As a result, his conclusions were all over the place, but a
thorough re-evaluation of his observations could provide interesting
results.

However, L&C made an immense journey, and it would be far more to tackle
than I could possibly manage myself. It could be an interesting joint
project, split up into lengths between cooperating workers. Anyone
interested?

George.

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contact George Huxtable by email at george@huxtable.u-net.com, by phone at
01865 820222 (from outside UK, +44 1865 820222), or by mail at 1 Sandy
Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
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