re called, which differ in no respect from the
common ones but in their being brighter than the rest of the sun's
surface.[24]

[23] The original of this letter is in the British Museum.

[24] See Istoria e Dimonstrazioni, intorno alle macchie solare.
_Roma_, 1616. See Opere di Galileo, vol, v., p. 131-293.

In the last of the letters which our author addressed to Velser, and
which was written in December 1612, he recurs to his former discovery of
the elongated shape, or rather the triple structure, of Saturn. The
singular figure which he had observed in this planet had entirely
disappeared; and he evidently announces the fact to Velser, lest it
should be used by his enemies to discredit the accuracy of his
observations. "Looking on Saturn," says he, "within these few days, I
found it solitary, without the assistance of its accustomed stars, and,
in short, perfectly round and defined like Jupiter; and such it still
remains. Now, what can be said of so strange a metamorphosis? Are the
two smaller stars consumed like the spots on the sun? Have they suddenly
vanished and fled? or has Saturn devoured his own children? or was the
appearance indeed fraud and illusion, with which the glasses have for so
long a time mocked me, and so many others who have often observed with
me? Now, perhaps, the time is come to revive the withering hopes of
those who, guided by more profound contemplations, have followed all the
fallacies of the new observations, and recognised their impossibilities.
I cannot resolve what to say in a chance so strange, so new, and so
unexpected; the shortness of the time, the unexampled occurrence, the
weakness of my intellect, and the terror of being mistaken, have greatly
confounded me." Although Galileo struggled to obtain a solution of this
mystery, yet he had not the good fortune to succeed. He imagined that
the two smaller stars would reappear, in consequence of the supposed
revolution of the planet round its axis; but the discovery of the ring
of Saturn, and of the obliquity of its plane to the ecliptic, was
necessary to explain the phenomena which were so perplexing to our
author.

The ill health to which Galileo was occasionally subject, and the belief
that the air of Florence was prejudicial to his complaints, induced him
to spend much of his time at Selve, the villa of his friend Salviati.
This eminent individual had ever been the warmest friend of Galileo, and
seems to have deligh