convert to this theory at an early day. He was not enabled,
however, to make any marked contribution to the subject, beyond
the influence of his general teachings, until about the year
1610. The brilliant contributions which he made were due largely
to a single discovery--namely, that of the telescope. Hitherto
the astronomical observations had been made with the unaided eye.
Glass lenses had been known since the thirteenth century, but,
until now, no one had thought of their possible use as aids to
distant vision. The question of priority of discovery has never
been settled. It is admitted, however, that the chief honors
belong to the opticians of the Netherlands.

As early as the year 1590 the Dutch optician Zacharias Jensen
placed a concave and a convex lens respectively at the ends of a
tube about eighteen inches long, and used this instrument for the
purpose of magnifying small objects--producing, in short, a crude
microscope. Some years later, Johannes Lippershey, of whom not
much is known except that he died in 1619, experimented with a
somewhat similar combination of lenses, and made the startling
observation that the weather-vane on a distant church-steeple
seemed to be brought much nearer when viewed through the lens.
The combination of lenses he employed is that still used in the
construction of opera-glasses; the Germans still call such a
combination a Dutch telescope.

Doubtless a large number of experimenters took the matter up and
the fame of the new instrument spread rapidly abroad. Galileo,
down in Italy, heard rumors of this remarkable contrivance,
through the use of which it was said "distant objects might be
seen as clearly as those near at hand." He at once set to work to