It is not by any means proposed to inflict upon you a history of the
telescope, but your indulgence is asked for a few moments while
reference is made to one or two matters connected with its invention,
or, rather, its accidental discovery and subsequent improvement.
The opening years of the seventeenth century found the world without a
telescope, or, at least, such an instrument as was adapted for
astronomical work. It is true that long years before, Arabian and some
other eastern astronomers, for the purpose, possibly, of enabling them
to concentrate their gaze upon celestial objects and follow their
motions, had been accustomed to use a kind of tube consisting of a
long cylinder without glasses of any kind and open at both ends. For
magnifying purposes, this tube was of no value. Still, it must have
been of some kind of service, or else the first telescopes, as
constructed by the spectacle makers, who had stumbled upon the
principle involved, were exceedingly sorry affairs, for, soon after
their introduction, the illustrious Kepler, in his work on "Optics,"
recommended the employment of plain apertures, without lenses, because
they were superior to the telescope on account of their freedom from
refraction.
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