Their observations, recorded by Barbican, were vigorously remade,
revised, and re-determined, by the others. To make them, they had
telescopes which they now began to employ with great advantage. To
regulate and investigate them, they had the best maps of the day.
Whilst occupied in this silent work, they could not help throwing a
short retrospective glance on the former Observers of the Moon.
The first of these was Galileo. His slight telescope magnified only
thirty times, still, in the spots flecking the lunar surface, like the
eyes checkering a peacock's tail, he was the first to discover mountains
and even to measure their heights. These, considering the difficulties
under which he labored, were wonderfully accurate, but unfortunately he
made no map embodying his observations.
A few years afterwards, Hevel of Dantzic, (1611-1688) a Polish
astronomer--more generally known as Hevelius, his works being all
written in Latin--undertook to correct Galileo's measurements. But as
his method could be strictly accurate only twice a month--the periods of
the first and second quadratures--his rectifications could be hardly
called successful.
Still it is to the labors of this eminent astronomer, carried on
uninterruptedly for fifty years in his own observatory, that we owe the
first map of the Moon.
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