prediction, based on a preconceived hypothesis. Gilbert found the
dip to be 72 degrees at London; eight years later Hudson found
the dip at 75 degrees 22' north latitude to be 89 degrees 30';
but it was not until over two hundred years later, in 1831, that
the vertical dip was first observed by Sir James Ross at about 70
degrees 5' north latitude, and 96 degrees 43' west longitude.
This was not the exact point assumed by Gilbert, and his
scientific predictions, therefore, were not quite correct; but
such comparatively slight and excusable errors mar but little the
excellence of his work as a whole.

A brief epitome of some of his other important discoveries
suffices to show that the exalted position in science accorded
him by contemporaries, as well as succeeding generations of
scientists, was well merited. He was first to distinguish between
magnetism and electricity, giving the latter its name. He
discovered also the "electrical charge," and pointed the way to
the discovery of insulation by showing that the charge could be
retained some time in the excited body by covering it with some
non-conducting substance, such as silk; although, of course,
electrical conduction can hardly be said to have been more than
vaguely surmised, if understood at all by him. The first
electrical instrument ever made, and known as such, was invented
by him, as was also the first magnetometer, and the first
electrical indicating device. Although three centuries have
elapsed since his death, the method of magnetizing iron first
introduced by him is in common use to-day.

He made exhaustive experiments with a needle balanced on a pivot
to see how many substances he could find which, like amber, on