when the philosopher chances to be a seaman on a very
dangerous coast, it will be admitted that the strength of this confidence
is put to a test somewhat more severe; and we find nevertheless that
Captain Flinders staked the safety of his ship and the existence of
himself and his crew on the truth of the above proposition." (* Edinburgh
Review, January, 1807; Flinders' Paper, "Observations on the Marine
Barometer," was published in the Philosophical Transactions of the Royal
Society, Part 2 1806.) Nowadays, indeed, the principal use of a barometer
to a navigator aboard ship is to enable him to anticipate changes of
wind.

Not less important were his experiments and writings upon variations of
the compass aboard ship. The fact that the needle of a compass showed
deviations on being moved from one part of a ship to another had been
observed by navigators in the eighteenth century, but Flinders was the
first to experiment systematically to ascertain the cause and to invent a
remedy.* (* For the history of the matter see Alexander Smith's
Introduction to W. Scoresby's Journal of a Voyage to Australia for
Magnetic Research, 1859.)

He observed not only that the direction of the needle varied according to
the part of the ship where it was placed, but also that a change in the
direction of the ship's head made a difference. Further, he found that in
northern latitudes (in the English Channel, for instance) the north end
of the needle was attracted towards the bow of the ship; whilst in
southern latitudes, in Bass Strait, there was an attraction towards the
stern; and at the equator there was no deviation. He came to the
conclusion that these results were due to the presence of iron in the
ship. When he returned to England in 1810, he wrote a memorandum on the
subject to the Admiralty, and requested that experiments might be made
upon ships of the Navy, with the object of verifying a law which he had
deduced from a long series of observations. His conclusion was that "the
magnetism of the earth and the attraction forward in the ship must act
upon the needle in the nature of a compound force, and that errors
produced by the attraction should be proportionate to the sines of the
angles between the ship's head and the magnetic meridian." Experiments
were made at Sheerness, Portsmouth, and Plymouth on five vessels. He took
a keen personal interest in them; and the result was his invention of the
Flinders' bar, which is now used in