emoir so brief and general as the present, it would be out of
place to discuss the history of this extraordinary invention. We have no
hesitation in asserting that a method of magnifying distant objects was
known to Baptista Porta and others; but it seems to be equally certain
that an _instrument_ for producing these effects was first constructed
in Holland, and that it was from that kingdom that Galileo derived the
knowledge of its existence. In considering the contending claims, which
have been urged with all the ardour and partiality of national feeling,
it has been generally overlooked, _that a single convex lens_, whose
focal length exceeds the distance at which we examine minute objects,
performs the part of a telescope, when an eye, placed behind it, sees
distinctly the inverted image which it forms. A lens, twenty feet in
focal length, will in this manner magnify twenty times; and it was by
the same principle that Sir William Herschel discovered a new satellite
of Saturn, by using only the mirror of his forty-feet telescope. The
instrument presented to Prince Maurice, and which the Marquis Spinola
found in the shop of John Lippershey, the spectacle maker of Middleburg,
must have been an astronomical telescope consisting of two convex
lenses. Upon this supposition, it differed from that which Galileo
constructed; and the Italian philosopher will be justly entitled to the
honour of having invented that form of the telescope which still bears
his name, while we must accord to the Dutch optician the honour of
having previously invented the astronomical telescope.

The interest which the exhibition of the telescope excited at Venice did
not soon subside: Sirturi[10] describes it as amounting almost to
phrensy. When he himself had succeeded in making one of these
instruments, he ascended the tower of St Mark, where he might use it
without molestation. He was recognised, however, by a crowd in the
street; and such was the eagerness of their curiosity, that they took
possession of the wondrous tube, and detained the impatient philosopher
for several hours, till they had successively witnessed its effects.
Desirous of obtaining the same gratification for their friends, they
endeavoured to learn the name of the inn at which he lodged; but Sirturi
fortunately overheard their inquiries, and quitted Venice early next
morning, in order to avoid a second visitation of this new school of
philosophers. The opticians speedily avai