Global Positioning System Reference
In-Depth Information
FIGURE 7.9.
John Harrison's fifth and most accurate marine chronometer, H5.
Figure
courtesy of Racklever.
the prize money. After intervention by the king and parliament on Har-
rison's behalf, he eventually received half the prize money. Meanwhile, he
designed and constructed H5 (fig. 7.9), which, trials in 1772 showed, kept
time with an error of less than a third of a second per day.
An expertly made copy of H4 accompanied Cook on his second voyage,
which lasted three years. The captain expressed himself entirely satisfied
with it; his experience demonstrated that the marine chronometer ap-
proach to longitude estimation worked not just on sea trials, but on real
maritime expeditions.
In recent years John Harrison has received a great deal of attention in
the literature for solving the longitude problem. He did so, but we must
also give credit to other advocates of the marine chronometer method.
Many of the advances in horology during this period came from France
(from master horologist Pierre le Roy in particular). Because the Harrison
deflection of a plumb line due to the gravitational attraction of a mountain—Schiehallion,
in Scotland. Maskelyne was assisted in this experiment by Reuben Burrow, a gifted but
pugnacious commoner who, like Harrison, felt that he was not given due credit for his
contributions. See, e.g., Danson (2006).
