nt of Galileo.
He had calculated, however, too securely on his means of putting the new
method to a successful trial. The great imperfection of the time-keepers
of that day, and the want of proper telescopes, would have baffled him
in all his efforts, and he would have been subject to a more serious
mortification from the failure and rejection of his plan, than that
which he actually experienced from the avarice of his patron, or the
indifference of Spain. Even in the present day, no telescope has been
invented which is capable of observing at sea the eclipses of Jupiter's
satellites; and though this method of finding the longitude has great
advantages on shore, yet it has been completely abandoned at sea, and
superseded by easier and more correct methods.

In the year 1618, when no fewer than _three_ comets visited our system,
and attracted the attention of all the astronomers of Europe, Galileo
was unfortunately confined to his bed by a severe illness; but, though
he was unable to make a single observation upon these remarkable bodies,
he contrived to involve himself in the controversies which they
occasioned. Marco Guiducci, an astronomer of Florence, and a friend of
Galileo, had delivered a discourse on comets before the Florentine
Academy. The heads of this discourse, which was published in 1619,[30]
were supposed to have been communicated to him by Galileo, and this
seems to have been universally admitted during the controversy to which
it gave rise. The opinion maintained in this treatise, that comets are
nothing but meteors which occasionally appear in our atmosphere, like
halos and rainbows, savours so little of the sagacity of Galileo that we
should be disposed to question its paternity. His inability to partake
in the general interest which these three comets excited, and to employ
his powerful telescope in observing their phenomena, and their
movements, might have had some slight share in the formation of an
opinion which deprived them of their importance as celestial bodies.
But, however this may have been, the treatise of Guiducci afforded a
favourable point of attack to Galileo's enemies, and the dangerous task
was entrusted to Horatio Grassi, a learned Jesuit, who, in a work
entitled _The Astronomical and Philosophical Balance_, criticised the
discourse on comets, under the feigned name of Lotario Sarsi.

[30] Discorso delle Comete. Printed in the Opere di Galileo, vol.
vi., pp. 117-191.

Ga