_Galileo at Arcetri—Becomes Blind—Moon's Libration—Publication of
the Dialogues on Motion._
WE have already alluded to the imperfect state of the knowledge
possessed with regard to Galileo's domestic life and personal habits;
there is reason however to think that unpublished materials exist from
which these outlines might be in part filled up. Venturi informs us that
he had seen in the collection from which he derived a great part of the
substance of his Memoirs of Galileo, about one hundred and twenty
manuscript letters, dated between the years 1623 and 1633, addressed to
him by his daughter Maria, who with her sister had attached herself to
the convent of St. Matthew, close to Galileo's usual place of residence.
It is difficult not to think that much interesting information might be
obtained from these, with respect to Galileo's domestic character. The
very few published extracts confirm our favourable impressions of it,
and convey a pleasing idea of this his favourite daughter. Even when, in
her affectionate eagerness to soothe her father's wounded feelings at
the close of his imprisonment in Rome, she dwells with delight upon her
hopes of being allowed to relieve him, by taking on herself the
penitential recitations which formed a part of his sentence, the
prevalent feeling excited in every one by the perusal must surely be
sympathy with the filial tenderness which it is impossible to
misunderstand.
The joy she had anticipated in again meeting her parent, and in
compensating to him by her attentive affection the insults of his
malignant enemies, was destined to be but of short duration. Almost in
the same month in which Galileo returned to Arcetri she was seized with
a fatal illness; and already in the beginning of April, 1634, we learn
her death from the fruitless condolence of his friends. He was deeply
and bitterly affected by this additional blow, which came upon him when
he was himself in a weak and declining state of health, and his answers
breathe a spirit of the most hopeless and gloomy despondency.
In a letter written in April to Bocchineri, his son's father-in-law, he
says: "The hernia has returned worse than at first: my pulse is
intermitting, accompanied with a palpitation of the heart; an
immeasurable sadness and melancholy; an entire loss of appetite; I am
hateful to myself; and in short I feel that I am called incessantly by
my dear daughter. In this state, I do not think it advisable that
Vincenzo should set out on his journey, and leave me, when every hour
something may occur, which would make it expedient that he should be
here." In this extremity of ill health, Galileo requested leave to go to
Florence for the advantage of medical assistance; but far from obtaining
permission, it was intimated that any additional importunities would be
noticed by depriving him of the partial liberty he was then allowed to
enjoy. After several years confinement at Arcetri, during the whole of
which time he suffered from continual indisposition, the inquisitor
Fariano wrote to him in 1638, that the Pope permitted his removal to
Florence, for the purpose of recovering his health; requiring him at the
same time to present himself at the Office of the Inquisition, where he
would learn the conditions on which this favour had been granted. These
were that he should neither quit his house nor receive his friends
there; and so closely was the letter of these instructions adhered to,
that he was obliged to obtain a special permission to go out to attend
mass during Passion week. The strictness with which all personal
intercourse with his friends was interrupted, is manifest from the
result of the following letter from the Duke of Tuscany's secretary of
state to Nicolini, his ambassador at Rome. "Signor Galileo Galilei, from
his great age and the illnesses which afflict him, is in a condition
soon to go to another world; and although in this the eternal memory of
his fame and value is already secured, yet his Highness is greatly
desirous that the world should sustain as little loss as possible by his
death; that his labours may not perish, but for the public good may be
brought to that perfection which he will not be able to give them. He
has in his thoughts many things worthy of him, which he cannot be
prevailed on to communicate to any but Father Benedetto Castelli, in
whom he has entire confidence. His Highness wishes therefore that you
should see Castelli, and induce him to procure leave to come to Florence
for a few months for this purpose, which his Highness has very much at
heart; and if he obtains permission, as his Highness hopes, you will
furnish him with money and every thing else he may require for his
journey." Castelli, it will be remembered, was at this time salaried by
the court of Rome. Nicolini answered that Castelli had been himself to
the Pope to ask leave to go to Florence. Urban immediately intimated his
suspicions that his design was to see Galileo, and upon Castelli's
stating that certainly it would be impossible for him to refrain from
attempting to see him, he received permission to visit him in the
company of an officer of the Inquisition. At the end of some months
Galileo was remanded to Arcetri, which he never again quitted.
In addition to his other infirmities, a disorder which some years before
had affected the sight of his right eye returned in 1636; in the course
of the ensuing year the other eye began to fail also, and in a few
months he became totally blind. It would be difficult to find any even
among those who are the most careless to make a proper use of the
invaluable blessing of sight, who could bear unmoved to be deprived of
it, but on Galileo the loss fell with peculiar and terrible severity; on
him who had boasted that he would never cease from using the senses
which God had given him, in declaring the glory of his works, and the
business of whose life had been the splendid fulfilment of that
undertaking. "The noblest eye is darkened," said Castelli, "which nature
ever made: an eye so privileged, and gifted with such rare qualities,
that it may with truth be said to have seen more than all of those who
are gone, and to have opened the eyes of all who are to come." His own
patience and resignation under this fatal calamity are truly wonderful;
and if occasionally a word of complaint escaped him, it was in the
chastened tone of the following expressions—"Alas! your dear friend and
servant Galileo has become totally and irreparably blind; so that this
heaven, this earth, this universe, which with wonderful observations I
had enlarged a hundred and thousand times beyond the belief of by-gone
ages, henceforward for me is shrunk into the narrow space which I myself
fill in it.—So it pleases God: it shall therefore please me also."
Hopes were at first entertained by Galileo's friends, that the
blindness was occasioned by cataracts, and that he might look forward to
relief from the operation of couching; but it very soon appeared that
the disorder was not in the humours of the eye, but in a cloudiness of
the cornea, the symptoms of which all external remedies failed to
alleviate.
As long as the power was left him, he had indefatigably continued his
astronomical observations. Just before his sight began to decay, he had
observed a new phenomenon in the moon, which is now known by the name of
the moon's libration, the nature of which we will shortly explain. A
remarkable circumstance connected with the moon's motion is, that the
same side is always visible from the earth, showing that the moon turns
once on her own axis in exactly the time of her monthly revolution.[114]
But Galileo, who was by this time familiar with the whole of the moon's
visible surface, observed that the above-mentioned effect does not
accurately take place, but that a small part on either side comes
alternately forward into sight, and then again recedes, according to the
moon's various positions in the heavens. He was not long in detecting
one of the causes of this apparent libratory or rocking motion. It is
partly occasioned by our distance as spectators from the centre of the
earth, which is also the centre of the moon's motion. In consequence of
this, as the moon rises in the sky we get an additional view of the
lower half, and lose sight of a small part of the upper half which was
visible to us while we were looking down upon her when low in the
horizon. The other cause is not quite so simple, nor is it so certain
that Galileo adverted to it: it is however readily intelligible even to
those who are unacquainted with astronomy, if they will receive as a
fact that the monthly motion of the moon is not uniform, but that she
moves quicker at one time than another, whilst the motion of rotation on
her own axis, like that of the earth, is perfectly uniform. A very
little reflection will show that the observed phenomenon will
necessarily follow. If the moon did not turn on her axis, every side of
her would be successively presented, in the course of a month, towards
the earth; it is the motion of rotation which tends to carry the newly
discovered parts out of sight.
Let us suppose the moon to be in that part of her orbit where she moves
with her average motion, and that she is moving towards the part where
she moves most quickly. If the motion in the orbit were to remain the
same all the way round, the motion of rotation would be just sufficient
at every point to bring round the same part of the moon directly in
front of the earth. But since, from the supposed point, the moon is
moving for some time round the earth with a motion continually growing
quicker, the motion of rotation is not sufficiently quick to carry out
of sight the entire part discovered by the motion of translation. We
therefore get a glimpse of a narrow strip on the side _from_ which the
moon is moving, which strip grows broader and broader, till she passes
the point where she moves most swiftly, and reaches the point of average
swiftness on the opposite side of her orbit. Her motion is now
continually growing slower, and therefore from this point the motion of
rotation is too swift, and carries too much out of sight, or in other
words, brings into sight a strip on the side _towards_ which the moon is
moving. This increases till she passes the point of least swiftness, and
arrives at the point from which we began to trace her course, and the
phenomena are repeated in the same order.
This interesting observation closes the long list of Galileo's
discoveries in the heavens. After his abjuration, he ostensibly withdrew
himself in a great measure from his astronomical pursuits, and employed
himself till 1636 principally with his Dialogues on Motion, the last
work of consequence that he published. In that year he entered into
correspondence with the Elzevirs, through his friend Micanzio, on the
project of printing a complete edition of his writings. Among the
letters which Micanzio wrote on the subject is one intimating that he
had enjoyed the gratification, in his quality of Theologian to the
Republic of Venice, of refusing his sanction to a work written against
Galileo and Copernicus. The temper however in which this refusal was
announced, contrasts singularly with that of the Roman Inquisitors. "A
book was brought to me which a Veronese Capuchin has been writing, and
wished to print, denying the motion of the earth. I was inclined to let
it go, to make the world laugh, for the ignorant beast entitles every
one of the twelve arguments which compose his book, 'An irrefragable and
undeniable demonstration,' and then adduces nothing but such childish
trash as every man of sense has long discarded. For instance, this poor
animal understands so much geometry and mathematics, that he brings
forward as a demonstration, that if the earth could move, having nothing
to support it, it must necessarily fall. He ought to have added that
then we should catch all the quails. But when I saw that he speaks
indecently of you, and has had the impudence to put down an account of
what passed lately, saying that he is in possession of the whole of your
process and sentence, I desired the man who brought it to me to go and
be hanged. But you know the ingenuity of impertinence; I suspect he will
succeed elsewhere, because he is so enamoured of his absurdities, that
he believes them more firmly than his Bible."
After Galileo's condemnation at Rome, he had been placed by the
Inquisition in the list of authors the whole of whose writings, '_edita
et edenda_,' were strictly forbidden. Micanzio could not even obtain
permission to reprint the Essay on Floating Bodies, in spite of his
protestations that it did not in any way relate to the Copernican
theory. This was the greatest stigma with which the Inquisition were in
the habit of branding obnoxious authors; and, in consequence of it, when
Galileo had completed his Dialogues on Motion, he found great difficulty
in contriving their publication, the nature of which may be learned from
the account which Pieroni sent to Galileo of his endeavours to print
them in Germany. He first took the manuscript to Vienna, but found that
every book printed there must receive the approbation of the Jesuits;
and Galileo's old antagonist, Scheiner, happening to be in that city,
Pieroni feared lest he should interfere to prevent the publication
altogether, if the knowledge of it should reach him. Through the
intervention of Cardinal Dietrichstein, he therefore got permission to
have it printed at Olmutz, and that it should be approved by a
Dominican, so as to keep the whole business a secret from Scheiner and
his party; but during this negociation the Cardinal suddenly died, and
Pieroni being besides dissatisfied with the Olmutz type, carried back
the manuscript to Vienna, from which he heard that Scheiner had gone
into Silesia. A new approbation was there procured, and the work was
just on the point of being sent to press, when the dreaded Scheiner
re-appeared in Vienna, on which Pieroni again thought it advisable to
suspend the impression till his departure. In the mean time his own duty
as a military architect in the Emperor's service carried him to Prague,
where Cardinal Harrach, on a former occasion, had offered him the use of
the newly-erected University press. But Harrach happened not to be at
Prague, and this plan like the rest became abortive. In the meantime
Galileo, wearied with these delays, had engaged with Louis Elzevir, who
undertook to print the Dialogues at Amsterdam.
It is abundantly evident from Galileo's correspondence that this edition
was printed with his full concurrence, although, in order to obviate
further annoyance, he pretended that it was pirated from a manuscript
copy which he sent into France to the Comte de Noailles, to whom the
work is dedicated. The same dissimulation had been previously thought
necessary, on occasion of the Latin translation of "The Dialogues on the
System," by Bernegger, which Galileo expressly requested through his
friend Deodati, and of which he more than once privately signified his
approbation, presenting the translator with a valuable telescope,
although he publicly protested against its appearance. The story which
Bernegger introduced in his preface, tending to exculpate Galileo from
any share in the publication, is by his own confession a mere fiction.
Noailles had been ambassador at Rome, and, by his conduct there, well
deserved the compliment which Galileo paid him on the present occasion.
As an introduction to the account of this work, which Galileo considered
the best he had ever produced, it will become necessary to premise a
slight sketch of the nature of the mechanical philosophy which he found
prevailing, nearly as it had been delivered by Aristotle, with the same
view with which we introduced specimens of the astronomical opinions
current when Galileo began to write on that subject: they serve to show
the nature and objects of the reasoning which he had to oppose; and,
without some exposition of them, the aim and value of many of his
arguments would be imperfectly understood and appreciated.
FOOTNOTES:
[114] Frisi says that Galileo did not perceive this conclusion (Elogio
del Galileo); but see The Dial. on the System, Dial. 1. pp. 61, 62, 85.
Edit. 1744. Plutarch says, (De Placitis Philos. lib. ii. c. 28,) that
the Pythagoreans believed the moon to have inhabitants fifteen times as
large as men, and that their day is fifteen times as long as ours. It
seems probable, that the former of these opinions was engrafted on the
latter, which is true, and implies a perception of the fact in the text.