MARGINALIA
Finding Out the Longitude
J. Donald Fernie
The Board of Longitude
Even decades after the founding of the royal observatories, the
astronomers were not making much progress on the longitude problem,
and meanwhile lives and valuable cargoes continued to be lost to
shipwreck. Several maritime nations offered considerable rewards to
anyone who could solve the problem adequately. In 1714 Britain
offered a prize of £20,000 to anyone who could convince a
panel of experts, known as the Board of Longitude, of a method that
would determine longitude to within half a degree after a
trans-Atlantic voyage. A sum of that magnitude, worth millions of
dollars in today's terms, was, of course, a clarion call to every
crackpot everywhere.
Very soon the Board of Longitude needed a secretary to hand out
stereotypical answers to stereotypical proposals. Some applicants
simply had no idea what the longitude problem was about. Thus Dr.
Woeman wrote, "acquainting the Board that he can express p and
the ratio of 1 to -2 in integrals, and that this comprehends the
discovery of the Longitude." Others had some inkling of the
problem but proposed hopelessly naive solutions. Mr. Owen Straton,
for instance, had to be informed that a sundial would not win the
prize. Only slightly better on the scale of naivete was Mr.
Haldanby's offering, which noted that sailing northwest near the
equator meant that having increased your latitude by 1 degree, you
had also moved 1 degree westward in longitude, and that he could
provide a table that would apply to other latitudes and directions.
The difficulties introduced by ocean currents seem not to have
occurred to him.
A proposal that received a good deal of attention beyond the Board
was that of Whiston and Ditton. William Whiston had succeeded Isaac
Newton as Lucasian Professor at the University of Cambridge, and so
his opinions on scientific matters carried some weight. The
Whiston-Ditton scheme envisioned small ships being anchored at
intervals of a few hundred miles across an ocean, it being
"known" that the North Atlantic was nowhere more than 300
fathoms deep. Each ship would have a powerful gun that would fire a
shell 6,440 feet vertically upward at midnight each night. At the
apex of its ascent, the shell would explode with a brilliant flash
and monstrous boom that could be seen and later heard as much as a
hundred miles away. This would allow other ships to locate
themselves relative to the anchored ship, whose longitude would have
been established by, say, lunar eclipses. Problems of staffing and
provisioning such ships, keeping enemy ships and pirates at bay, and
so forth, were waved away. A competitor noted that this proposal was
"a very whimsical Notion, looking very Ridiculous in Mr Ditton
and Mr Whiston; the first of which Gentlemen I do not know, but as
for the other, People says he is a little beside himself, or rather,
if he has any such Thing as Brains, they are really crackt."
But the pièce de résistance of all such
schemes was the one based on "the powder of sympathy." Its
author was anonymous and very likely wrote satirically (since
anonymous inventors are not usually awarded major prizes). The
method hinged on a medicinal powder that when applied to a wound
would cause the wounded person to start up, possibly with a cry.
Nothing unusual there, but the author claimed to have found that if
the powder was applied not to the wound itself but to a bandage that
had previously been on the wound, the effect was the same. Thus it
was proposed that each ship carry a wounded dog, and that a bandage
from the wound be left at Greenwich, where at precisely noon each
day it would be dipped into a solution of the powder of sympathy.
The dog, wherever in the world its ship was at that moment, would
then obligingly yelp and the mariner could then note the local time
and so find his longitude.
As the years went by, the preferred methods of finding longitude
narrowed to two: improvements to the method of lunar distances and
improvements in the marine chronometer. Lunar distances continued in
use well into the 19th century, but in the end it was the
chronometer that won out, and in our own time, of course, radio
signals and now the Global Positioning System have reduced the
problem to triviality.
© J. Donald Fernie
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