Next message: Alexandre E Eremenko: "Re: Timing Lunars with a Rock"
Come on, Bruce, your memory is as bad as Jared's, when you write-
>The old navigation manuals suggested checking the log line and half minute
>glass occasionally. One way to check the glass was by pendulum. As I
>recall, the length of the pendulum, to the center of the musket ball that
>formed the weight, was sometimes given as 29 and 1/4 inches, and sometimes
>as 29 and 1/8. Count a second each time the pendulum passed the bottom. I
>suppose you had to give the pendulum a few moments to settle the length of
>its swing.
>
>Bruce
It's not 29 and-a-bit, but 39 and-a-bit inches, which I have just confirmed
by working it out from the expression for a period of 2 seconds as 2 x pi x
sguare-root-of( length / gravity acceleration ). And to be doubly sure,
I've just checked it against the pendulum of my old grandfather clock in
the hall. 39 and-a-bit it is.
What a mess listmembers would make of estimating time at an African lake,
if that's the best they can do between them!
George.
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