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> I hope we'll be hearing more from you about the surveyors.

I will certainly share anything I find.

> Here are the tables as listed in the "Contents."

[list deleted]

> That's the end of the tables.

Thank you Bruce, that is very helpful!

> I doubt Robertson's book was much used outside the classroom. Have you
> seen it? Clearly put together to exercise the minds of students. Not a
> practical manual.

I have not seen it but the Hudson Bay records clearly show it being
ordered and delivered to David Thompson.

> Moore is more likely the one your surveyors used. It
> incorporates most of Maskelyne and also has the traverse tables, etc.
> needed for regular navigation. Unlike Robertson, it's small and handy.

I discovered that our library has a copy of Moore in their special
collection and I went over on Friday afternoon to look at it. It's not in
great shape so they wouldn't let me photocopy anything but I did copy
out the two algorithms given for clearing the distance (barely, as the
special collections reading room closes at 4:30 so I didn't have much
time). When I get a moment I'll convert those instructions into math to
see what methods they correspond to. The tables seem to correlate well
with what was in Maskelyne's Tables Requisite (but again, I was pressed
for time).

> Do you have any of the surveyors' lunar distance data?

Unfortunately I do not. I have the example used by Jeff Gottfred (and I
will write him to see if he will share some of the data he has obtained
from the Archives of Ontario (where thousands of pages of David
Thompson's observations and calculations are stored)). I also have a
table of observations with the calculated longitude (but not the
calculations) from Philip Turnor in 1790 (p. 352 of the Champlain Society
volume dedicated to the journals of Samuel Hearne and Philip Turnor).
Come to think of it, the editor of Thompson's Columbia Journals is here
at the U of C and she must have a good deal of his observations and
calculations; perhaps I'll pay her a visit too.

Ken Muldrew

   

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