Lewis: July 15, 1804
On this Sunday, Lewis discovered that his chronometer had stopped, despite having been wound the previous noon. This was the third such incident since he acquired the instrument, though the first since leaving River Dubois. Based on past experience, he concluded the works were undamaged and the device's known error rate of 15.5 seconds slow per 24 hours remained reliable. He decided to halt at the next convenient location to make observations that would reset the chronometer's error, fix latitude and longitude, determine magnetic variation, and establish a new point of departure.
Sunday July 15th This evening I discovered that my Chronometer had stoped,
nor can I assign any cause for this accedent; she had been wound up the
preceding noon as usual. This is the third instance in which this
instrument has stopt in a similar manner since she nas been in my
possession, tho the first only since our departure from the River Dubois.
in the two preceding cases when she was again set in motion, and her rate
of going determined by a series of equal altitudes of the sun taken for
that purpose, it was found to be the same precisely as that mentioned in
the preliminary remarks to these observations, or 15 s & 5 tenths too
slow in 24 h-as her rate of going after stoping, and begin again set in
motion has in two instances proved to be the same, I have concluded, that
whatever this impediment may procede from, it is not caused by any
material injury which her works have sustained, and that when she is in
motion, her error on mean time above stated, may be depended on as
accurate. In consequence of the chronometer’s having thus accedentally
stoped, I determined to come too at the first convenient place and make
such observations as were necessary to ascertain her error, establish the
Latitude & Longitude, and determine the variation of the nedle, in
order to fix a second point of departure.
Read this entry in modern English AI-translated
Sunday, July 15th. This evening I discovered that my chronometer had stopped, nor can I assign any cause for this accident; it had been wound up the preceding noon as usual. This is the third instance in which this instrument has stopped in a similar manner since it has been in my possession, though the first since our departure from the River Dubois. In the two preceding cases, when it was again set in motion and its rate of going determined by a series of equal altitudes of the sun taken for that purpose, it was found to be precisely the same as that mentioned in the preliminary remarks to these observations, or 15 and 5 tenths seconds too slow in 24 hours. As its rate of going after stopping and being set in motion again has in two instances proved to be the same, I have concluded that, whatever this impediment may proceed from, it is not caused by any material injury which its works have sustained, and that when it is in motion, its error on mean time stated above may be depended on as accurate.
In consequence of the chronometer having thus accidentally stopped, I determined to come to at the first convenient place and make such observations as were necessary to ascertain its error, establish the latitude and longitude, and determine the variation of the needle, in order to fix a second point of departure.
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