, 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 being rubbed
affected the needle. In this way he discovered that light substances
were attracted by alum, mica, arsenic, sealing-wax, lac sulphur, slags,
beryl, amethyst, rock-crystal, sapphire, jet, carbuncle, diamond,
opal, Bristol stone, glass, glass of antimony, gum-mastic, hard resin,
rock-salt, and, of course, amber. He discovered also that atmospheric
conditions affected the production of electricity, dryness being
unfavorable and moisture favorable.

Galileo's estimate of this first electrician is the verdict of
succeeding generations. "I extremely admire and envy this author," he
said. "I think him worthy of the greatest praise for the many new and
true observations which he has made, to the disgrace of so many vain and
fabling authors."

STUDIES OF LIGHT, HEAT, AND ATMOSPHERIC PRESSURE

We have seen that Gilbert was by no means lacking in versatility, yet
the investigations upon which his fame is founded were all pursued along
one line, so that the father of magnetism may be considered one of the
earliest of specialists in physical science. Most workers of the time,
on the other band, extended their investigations in many directions. The
sum total of scie