Descartes Never Met Galileo

Descartes remained in Rome until the beginning of spring.

He was currently meditating on his return to France, when the Pope named Cardinal Francesco Barberini, his nephew, to go there in the capacity of legate.

The Spanish for a long time thought of the court of Rome by:

• the number and credit of the staff they maintained there
• the large possessions they had in Italy

The Spanish suspected this Pope of having French inclinations, because he did not openly take an interest in the loss they had just made of the Valtellina.

It was to disabuse them or to appease them, that by a brief dated March 26, 1625, he sent his nephew as legate to France to ask the king:

1. that he have the Valtellina and all the forts that the French had taken handed over to his holiness’s hands
2. by his means the Grisons be deprived of their sovereignty over the Valtellina.

The king having been warned of these projects, sent word to Mr. de Béthune his ambassador in Rome, that this legation would not be agreeable to him. This is what obliged the Pope to have his nephew take measures more suitable to the dispositions of the court of France.

Descartes believed that it was fitting for a French gentleman to go and render civilities to a cardinal nephew, destined to perform in his country a function as important as this legation was.

The cardinal received them benevolently.

But because he was a lover of science, and a protector of those who made a profession of it, he did not hold Descartes quit of his duties for a visit or two, and for superficial compliments.

He liked him so well, that he wanted to honor him particularly with his friendship: Descartes on his side did not forget on his return to continue his assiduities with him during the short time he was in France, and to give him in all the rest of his life marks of his recognition, both by the presents he had him make of his books, and by testimonies of respects and devotion that he had presented to him from time to time through the ministry of his friends.

The legate embarked for France towards the beginning of April, leading with him a large number of scholars, among whom were Cavalier Del Pozzo, Girolamo Aleandro, Jean Louis Le Debonnaire, brother-in-law of the young Barclay, Giovanni Battista Doni, Louis Aubry Du Mesnil, and others.

Descartes left Rome around the same time, but he wanted to return by land so as not to lose the opportunity to see a country that he was glad to know. He passed through Tuscany, and he perhaps saw the court of the Grand Duke Ferdinand II who was still then very young and in minority, and who had succeeded his father Cosimo II in 1621.

If we believe Mr. Borel, we will not be allowed to doubt that he paid a visit to the people of the country who were “in reputation for skill and science,” and especially to the celebrated Galileo whom he was certainly to forget less than any other.

Galileo was then about 60 years old at the peak of his great reputation.

He was equally known and admired by the great and the small. There was no prince, no great lord who, passing through the place of his residence, did not make it a point of honor to visit him. Curious people left foreign countries expressly to come and see him, as they had done formerly on the subject of Livy, and in his time even with regard to Mr. Viète.

To all these considerations taken from Galileo’s side, Descartes could add some from his own that seemed not to be able to dispense him from seeing this great man. Borel affirms that Descartes had seen Galileo.

But Descartes did not see Galileo.

Descartes

I have never seen Galileo nor have had any communication with him. And so I could not have borrowed anything from him. I do not see anything in his books that I envy, nor almost anything that I would want to admit as my own. All the best is what there is of music. But those who know me would say that Galileo got his ideas from me rather than me getting my ideas from him. For I had written almost the same things 19 years ago while I had not yet been to Italy. I had given my writing to Mr. N who made a show of it, and wrote here and there about it as a thing that came from him.

Descartes never knew Galileo except by his reputation and by reading his books.

Yet Descartes knew Galileo quite badly if one finds that Galileo wrote nothing on music.

It is quite probable that he will have confused the son with the father on this occasion: which would not have happened to him, if he had seen him at his home, where he would not have failed to inquire about his family in the conversation.

Vincenzo Galilei was the father of Galileo Galilei.

• He was a Florentine gentleman, knowledgeable in mathematics, and particularly in music.

Vincenzo Galilei had an Italian work divided into 5 dialogues on ancient and modern music.

The work is esteemed, and the Italian Jesuit Giuseppe Biancani judges it necessary to reestablish the music of the ancients, and to correct that of the moderns.

There is no appearance that Mr. Descartes read any other treatise by Galileo than that one, concerning music.

Vincenzo Galilei, who had had his son instructed with as much care as if he had been legitimate, and heir to his goods, had not forgotten to inspire in him the inclination he had for music.

But he could not prevent it from turning almost entirely towards astronomy, after which one can say that geometry, and mechanics held the first rank in his mind among mathematics.

For the rest, Descartes did not know much about Galileo, other than his condemnation and imprisonment at the inquisition.

which made too much of a stir to be ignored by the least curious, we can say that he did not know any circumstance of his life. So that he seemed surprised, when

In 1640, Father Mersenne spoke to Descartes of Galileo still alive.

• Descartes thought that Galileo had died long ago.

Descartes had not yet crossed the borders of Tuscany, when he learned the news of the war that was lighting up between the republic of Genoa and the Duke of Savoy Charles Emmanuel 1st of this name.

The most Christian king having been informed of the bad cause of the Genoese, and seeing that these republicans were supported by the help of the King of Spain, had sent 10,000 men to the Duke of Savoy under the command of the Constable de Lesdiguières.

The Duke of Savoy was in person at this war, and his army reinforced with the help of France was of 25,000 footmen and 3,000 horses.

The constable who commanded the vanguard of which he had made a detached army corps, had already made himself master of the cities of Capriata, of Gua, of Novi.

He had defeated various Spanish, Neapolitan, Milanese parties.

He had laid siege to the place of Gavi, when Descartes arrived in his camp to see what would happen there.

Gavi was a city of the lordship of Genoa on the side of Milan, at an almost equal distance between Tortona towards the north, and Genoa towards the south.

It had a strong citadel built on a rock of the Apennine Mountains. It was flanked with bastions, which made the place of a very difficult access, and which had made the famous Barbarossa of the time of Francis 1st fail.

The constable, who in laughing made those who wanted to turn him away from this enterprise hope that Graybeard would do what Redbeard had not been able to do, gave such good order to everything, that having defeated a relief of 1000 men sent by the governor of Milan, and cut into pieces 300 men of the garrison in a sortie it had made, he made himself master of the city on April 23.

This success facilitated the approaches to the citadel. Having also made a battery that he had found a way to set up on a neighboring mountain that had been judged impracticable until then succeed from the outside, he obliged the governor to hand over the place to him by capitulation on April 30.

After the capture of this city, Descartes wanted to see the army of the Duke of Savoy, which reduced the entire Riviera di Ponente, and took from the Genoese 174 places in a very short time.

But the conquest was short. Descartes did not wait for the Genoese, and the Spanish to have begun to breathe and to recover, to leave the army.

He came straight to Turin, where he stopped for 2 days to see what was happening among the magistrate, and the people.

For what could concern the court, it was then very deserted by the absence of the Duke Charles Emmanuel, of the Prince of Piedmont Victor Amadeus, and of the Prince Thomas his children, who were all at the army.

There had been no Duchess of Savoy for more than 27 years, since Catherine Michelle of Austria, daughter of Philip 2nd King of Spain and of Elizabeth of France, had died on November 6, 1597.

But he had the satisfaction of seeing there the Princess of Piedmont Christina of France, daughter of the King Henry IV, and sister of the King Louis XIII, married from the beginning of the year 1619.

From Turin, he passed towards the middle of the month of May by the pass of Susa to re-enter France.

But he turned away a few leagues on the side of Savoy to examine the height of the Alps, and to make some observations there.

It was here where he had:

• guessed the cause of thunder
• found why it thunders more rarely in winter than in summer.

He noticed that the snows being heated and weighted by the sun, the slightest emotion of air was sufficient to make large piles suddenly fall, which were named in the country avalanches which imitated the noise of thunder well.

From this, he conjectured that thunder could come from clouds being on top of the other, the highest ones which are surrounded by a warmer air fall suddenly on the lowest ones.

The way in which he saw the snows of the Alps heated by the sun made him judge that the heat of the air which is around a superior cloud can condense it, and make it heavier little by little in such a way that the highest of its parts beginning the first to descend, knock down and carry with them a quantity of others, which also fall all together with a lot of noise on the inferior cloud.

He wanted to explain why thunder is more rare in winter than in summer in these quarters.

He noticed that the heat does not then rise so easily to the highest clouds to dissolve them.

This is why during the great heats, when after a northern wind of short duration one feels again a humid and suffocating heat, it is a sign that thunder must soon follow.

For it is a mark, according to him, that this northern wind having passed against the earth has chased the heat towards the place of the air where the highest clouds form.

This wind being then chased itself towards the place where the lowest ones form by the dilation of the inferior air that the hot vapors it contains cause: not only must the highest ones in condensing descend, but the lowest ones even remaining very rare, and finding themselves as if raised and repelled by this dilation of the inferior air must resist them in such a way that often they can prevent any part from falling to the ground.

The noise that is thus made above us must be heard much better because of the resonance of the air which is a resonant body, and it must be greater because of the snow that falls, than is that of the lavanches or avalanches in the Alps.

It is also enough that the parts of the superior clouds fall all together, or one after the other, sometimes faster, sometimes more slowly; and that the inferior clouds are more or less large or thick, and that they resist more or less, to make us understand where the difference of the noises of thunder can come from.

The same observations also contributed a lot to make him notice what the differences of lightning, whirlwinds, and lightning consist in; their origin and their effects. He was no less exact in the other observations that he made on the Alps.

This is what appears by the instructions that he gave several years later to Father Mersenne, who was to make a trip to Italy, and who had consulted him on the way to take the height of these mountains.

He tells him in the response he made to him at the end of the year 1639, that he could measure Mont Cenis being beyond Susa in Piedmont, because the plain is very even; and that he knew no better way to know the height of the mountains, than to measure them from two stations, according to the rules of practical geometry.