course of centuries, the variation of the compass, at any one
point, changes very widely. It is well known that in 1490 the
needle pointed east of north in the Mediterranean, as well as in
those portions of the Atlantic which were then navigated. Columbus
was therefore much astonished when, on his first voyage, in mid-
ocean, he found that the deviation was reversed, and was now
towards the west. It follows that a line of no variation then
passed through the Atlantic Ocean. But this line has since been
moving towards the east. About 1662 it passed the meridian of
Paris. During the two hundred and forty years which have since
elapsed, it has passed over Central Europe, and now, as we have
already said, passes through European Russia.

The existence of natural magnets composed of iron ore, and their
property of attracting iron and making it magnetic, have been
known from the remotest antiquity. But the question as to who
first discovered the fact that a magnetized needle points north
and south, and applied this discovery to navigation, has given
rise to much discussion. That the property was known to the
Chinese about the beginning of our era seems to be fairly well
established, the statements to that effect being of a kind that
could not well have been invented. Historical evidence of the use
of the magnetic needle in navigation dates from the twelfth
century. The earliest compass consisted simply of a splinter of
wood or a piece of straw to which the magnetized needle was
attached, and which was floated in water. A curious obstacle is
said to have interfered with the first uses of this instrument.
Jack is a superstitious fellow, and we may be sure that he was not
less so in former times than he is today. From his point of view
there was something uncanny in so very simple a contrivance as a