led themselves of the new
instrument. Galileo's tube,--or the double eye-glass, or the cylinder,
or the trunk, as it was then called, for Demisiano had not yet given it
the appellation of _telescope_,--was manufactured in great quantities,
and in a very superior manner. The instruments were purchased merely as
philosophical toys, and were carried by travellers into every corner of
Europe.

[10] De Telescopio.

The art of grinding and polishing lenses was at this time very
imperfect. Galileo, and those whom he instructed, were alone capable of
making tolerable instruments. It appears, from the testimony of Gassendi
and Gaertner, that, in 1634, a good telescope could not be procured in
Paris, Venice, or Amsterdam; and that, even in 1637, there was not one
in Holland which could shew Jupiter's disc well defined.

After Galileo had completed his first instrument, which magnified only
_three_ times, he executed a larger and a better one, with a power of
about _eight_. "At length," as he himself remarks, "sparing neither
labour nor expense," he constructed an instrument so excellent, that it
bore a magnifying power of more than _thirty_ times.

The first celestial object to which Galileo applied his telescope was
the moon, which, to use his own words, appeared as near as if it had
been distant only two semidiameters of the earth. He then directed it to
the planets and the fixed stars, which he frequently observed with
"incredible delight."[11]

[11] Incredibili animi jucunditate.

The observations which he made upon the moon possessed a high degree of
interest. The general resemblance of its surface to that of our own
globe naturally fixed his attention; and he was soon able to trace, in
almost every part of the lunar disc, ranges of mountains, deep hollows,
and other inequalities, which reverberated from their summits and
margins the rays of the rising sun, while the intervening hollows were
still buried in darkness. The dark and luminous spaces he regarded as
indicating seas and continents, which reflected, in different degrees,
the incidental light of the sun; and he ascribed the phosphorescence, as
it has been improperly called, or the secondary light, which is seen on
the dark limb of the moon in her first and last quarters, to the
reflection of the sun's light from the earth.

These discoveries were ill received by the followers of Aristotle.
According to their preconceived opinions, the moon was perfe