s to have had some
knowledge of the second; but the third was discovered by Hevelius, and
the fourth by Lagrange.

This curious discovery was the result of the last telescopic
observations of Galileo. Although his right eye had for some years lost
its power, yet his general vision was sufficiently perfect to enable him
to carry on his usual researches. In 1636, however, this affection of
his eye became more serious; and, in 1637, his left eye was attacked
with the same disease. His medical friends at first supposed that
cataracts were formed in the crystalline lens, and anticipated a cure
from the operation of couching. These hopes were fallacious. The disease
turned out to be in the cornea, and every attempt to restore its
transparency was fruitless. In a few months the white cloud covered the
whole aperture of the pupil, and Galileo became totally blind. This
sudden and unexpected calamity had almost overwhelmed Galileo and his
friends. In writing to a correspondent he exclaims, "Alas! your dear
friend and servant has become totally and irreparably blind. These
heavens, this earth, this universe, which by wonderful observation I had
enlarged a thousand times beyond the belief of past ages, are henceforth
shrunk into the narrow space which I myself occupy. So it pleases God;
it shall, therefore, please me also." His friend, Father Castelli,
deplores the calamity in the same tone of pathetic sublimity:--"The
noblest eye," says he, "which nature ever made, is darkened; an eye so
privileged, and gifted with such rare powers, that it may truly be said
to have seen more than the eyes of all that are gone, and to have
opened the eyes of all that are to come."

Although Galileo had been thwarted in his attempt to introduce into the
Spanish marine his new method of finding the longitude at sea, yet he
never lost sight of an object to which he attached the highest
importance. As the formation of correct tables of the motion of
Jupiter's satellites was a necessary preliminary to its introduction, he
had occupied himself for twenty-four years in observations for this
purpose, and he had made considerable progress in this laborious task.
After the publication of his "Dialogues on Motion," in 1636, he renewed
his attempts to bring his method into actual use. For this purpose he
addressed himself to Lorenzo Real, who had been the Dutch
Governor-General in India, and offered the free use of his method to the
States-General of Holla