MDMD2: Our Clock ...

[Dave Monroe]

"Each of us is to have his own twin Telescope, by Mr. Dollond, fitted
with the latest of his marvellous Achromatics,-- our Clock by Mr.
Ellicott,-- and of course the Sector by your Mr. Bird,-- none but the
best for this Party, I should say!" (M&D, Ch. 2, p. 13)

First up ...

"our Clock by Mr. Ellicott"

>From Thomas D. Cope. "A Cock Sent Thither by the Royal Society,"
Proceedings of the American Philosophical Society, Vol. 94, No. 3 (June
1950): 260-71 ...

"During the summer of 1760 the [Royal] Society was preparing to send
expeditions to St. Helena and to Sumatra to observe the transit of Venus
which was due to occur on June 5, 1761.  Rev. Nevil Maskelyne, with
Robert Waddington as assistant, was chosen to go to St. Helena.  Charles
Mason, with Jeremiah Dixon as assistant, was selected to observe in
Sumatra.  Among the instruments needed, clocks were listed by the
Astronomer Royal the Rev. James Bradley.  On July 3, 1760, Maskelyne
requested a clock with a pendulum compensated for temperature, to cost
about 20 pounds sterling.  On September 11, 1760, a time-piece at 20
guineas was ordered from Mr. John Ellicott.  On Novmener 13m 1760, Mr.
Ellicott reported his clock ready for delivery to Portsmouth and a man
ready to accompany it to supervise, and to instruct Mr. Mason in
assembling the clock.  And on December 27, 1760, Maskelyne and
waddington signed a receipt for 'a clock with a gridiron-pendulum' while
Mason and Dixon signed for 'a clock made by Mr. Ellicott.'  On December
23, 1760, Mr. Shelton was paid 34:16:6 [pounds].
   "These clocks were used in obsereving on St. Helena and at the Cape
of Good Hope and were brought back to London in the spring of 1762...."
(pp. 262-3)

Two separate clocks.  And Mason and Dixon did indeed use Ellicott's
clock on the Transit of Venus expedition, while Maskelyne used
Shelton's.  However, do note that ...

"... the clock of the Royal Society which Maskelyne had used on St.
Helena and on Barbados arrived as planned for the use of Mason and Dixon
in Pennsylvania." (p. 261)

Hence perhaps Danson's apparent confusion?   But note also ...

"... the clock which sailed with Cook and Green to the South Seas was
either the [Shelton] clock that Mason and Dixon used in the Forks of the
Brandywine or its identical twin.  And nowhere in all the literature has
there been even a hint of the existence of a twin." (p. 267)

"... the clock which was sent by the Royal Society to Mason and Dixon in
Pennsylvania was John Shelton's astronomical Regulator which is still
owned by the Society and today [1950] is keeping almost faultless time
in Burlington House, London." (p. 260)

See also ...

Maskelyne, Nevil.  "Observations on a Clock of Mr. John Shelton,
   Made at St. Helena."  Philosophical Transactions of the Royal
   Society  52 (2 ), Art. 66 (1762)

Mason, Charles.  "Observations for Proving the Going of Mr. Ellicott's
   Clock at St. Helena."  Phil. Trans.  52 (2), Art. 86 (1762)

Short, James.  "An Account of Mr. Mason's Paper, Concerning the
   Going of Mr. Ellicott's Clock at St. Helena."  Phil. Trans. 52 (2),
   Art. 87 (1762)

Then back to ...