Sunday, June 7, 2020

June 7, 1793. Jupiter's Satellites.

June 7, 1793. (Lat and Long) 
Excerpts from the journals of Alexander MacKenzie on his Voyage of Discovery, 227 years ago to-day.
 
      “The morning was clear and calm; and since we had been at this station the water had risen two inches; so that the current became still stronger…”

       “I last night observed an emersion of Jupiter’s first satellite, but inadvertently went to bed, without committing the exact time to writing: if my memory is correct, it was 8.18.10 by the timepiece.”


      As mentioned before, he is using Jupiter’s moons as a celestial clock to help determine their longitude. 

      “The canoe, which had been little better than a wreck, being now repaired, we proceeded…” They made about three miles before noon when they landed again to determine the latitude. He finds the latitude to be 55.2.51 North.  “I find that my time-piece was slow 1.32.23 apparent time; and made the longitude obtained 122.35.50 West of Greenwich.” 
As usual, his latitude figures are probably very close to his actual location, however maybe his memory of the exact time last night was not correct. His reckoning of longitude is off; this time he is actually about 20 west miles of that point. 

“From this place we proceeded....(8 ¼ miles), and encamped at seven o’clock. Mr. MacKay and the hunters walked the greatest part of the day, and in the course of their excursion killed a porcupine...During the day several Indian encampments were seen...The current had also lost some of its impetuosity during the greater part of the day.”
      Something different in the Kettle tonight.

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