Libri's research career in mathematics began while he was still an undergraduate and he published his first paper Memoria ... sopra la teoria dei numeri Ⓣ in 1820, the year in which he graduated from Pisa. It was an impressive start for the remarkable young mathematician, and his first contribution received considerable praise from many of the leading mathematicians of the day such as Babbage, Cauchy, and Gauss. Such was the quality of his early work, that he was appointed to the chair of Mathematical Physics at Pisa in 1823. However :-
... he was not a good teacher and, not relishing the position, managed to obtain permanent leave after just one academic year.The following year, being now in the fortunate position of having the title of Professor, being paid a professorial salary but having no commitments, he visited Paris and was well received by the top mathematicians of the day including Laplace, Poisson, Ampère, Fourier and Arago. He returned to Italy but, in 1830, he was involved in political problems there when he was implicated in a conspiracy to impose a new constitution on the Grand Duke of Tuscany. He chose to flee to France where he felt he had many scientific friends who would support him. Indeed he became a French citizen three years later and was, in that same year of 1833, elected to the Académie des Sciences to succeed Legendre. Libri certainly took his role in the Academy very seriously but there was some resentment caused by the fact that he was not a native Frenchman, and this was somewhat increased by his own rather arrogant nature.
Arago, the perpetual secretary of the Academy, helped him obtain a further appointment at the Collège de France in 1833 where he taught, and in the following year he was elected as assistant professor in the calculus of probabilities at the Sorbonne. His friendship with Arago was certainly helpful to Libri in obtaining prestigious posts yet soon this relationship went sour (although we do not know the reason for this) and by 1835 instead of being recognised as close friends, the pair were recognised as bitter enemies. Arago was a powerful figure in French mathematics at the time and counting him as an enemy meant that many in the mathematical establishment also became Libri's enemies. One such powerful figure was Liouville who worked for many years against Libri and the two would attack each other at every opportunity in meetings of the Academy.
Liouville was in many ways someone who Libri should not have competed with, for he was an outstanding mathematician who could usually come up with a more elegant proof of Libri's results than he could himself. As Rice points out in :-
A little-known consequence of these disputes is that Liouville made his famous announcement of Évariste Galois's important work on the theory of equations in response to an attack by Libri in 1843.Libri's early work was on mathematical physics, particularly the theory of heat. However he made many contributions to number theory and to the theory of equations. His best work during the 1830s and 1840s was undoubtedly his work on the history of mathematics. From 1838 to 1841 he published four volumes of Histoire des sciences mathématiques en Italie, depuis la rénaissanace des lettres jusqu'à la fin du dix-septième siècle Ⓣ. He intended to write a further two volumes, but never finished the task. It is an important work but suffers from over-praise of Italians at the expense of others. As Benedetto Croce wrote in 1947, it was:-
... excellent as a rich collection of uncommon knowledge and as a work of versatile learning and vivid mind, [but] not, however, as an example of what a history of science should be.One of the strengths of Libri's Histoire is the large number of quotes from original sources, so it was natural that Libri should be an enthusiastic collector of rare books and manuscripts. As he worked on his book through the 1830s he avidly collected and by 1841, when his work was published, he had about 1800 manuscripts including many which had previously been thought to be lost. In this category were manuscripts by Fermat, Descartes, Euler, d'Alembert and Arbogast. His collection included manuscripts by Galileo, Leibniz, Mersenne, and Gassendi and it was a collection which continued to grow so that by 1847 he owned about 40000 books.
Libri was appointed Inspector of the Libraries of France in 1841. In some ways this appointment might appear surprising since he had fallen out with most members of the Academy. On the other hand he was undoubtedly a great expert and he also had a friend, François Guizot, in the government who helped him secure the position. However it was soon reported that precious books and manuscripts were going missing from libraries and all these losses coincided with a visit to the library by Libri. This merited an investigation but eventually nothing came of it.
There was a Revolution in France in 1848 and, shortly after this, Libri was informed that a warrant was about to be issued for his arrest on suspicion of stealing precious books. The Revolution had removed his friend Guizot from the government and Libri was now exposed. He did not wait to be arrested but fled as quickly as possible to London where he claimed to be a political refugee of the French Revolution. Before leaving France he arranged for 30000 of his books and manuscripts to be sent to him in England.
He was well received in London and treated as a hero. He had a fellow Italian friend in Antonio Panizzi, the Director of the Library of the British Museum, and through him Libri made friends with De Morgan. Now Libri was able to convince his new friends that the charges against him were made by the French because he was an Italian. De Morgan wrote many articles in Libri's defence. For example he wrote:-
... in science he would not be a Frenchman, but remained an Italian. One of his great objects was to place Italian discovery, which the French historians had not treated fairly, in its proper rank. ... We suspect that political animosity generated this slander, and that a real belief in the minds of bad men that collectors always steal, and that the charge was therefore sure to be true.However, on 22 June 1850 he was convicted in France in his absence on the charges which had been brought against him of stealing valuable books and he was sentenced to 10 years in prison. Certainly Libri could not return to France. Although Libri had arrived in England without any money he was not poor for long. Where did his new wealth come from? Perhaps not surprisingly it came from the sale of many precious books and manuscripts which Libri happened to have with him when he arrived in London. In fact he made over one million francs from his sales of documents and books.
In 1861 Libri had two major sales of his books and manuscripts in England. He produced a catalogue containing 7628 lots which were sold in two parts, the first sale beginning on 25 April lasting 12 days, the second beginning on 18 July and lasting 8 days. He wrote a 30 page introduction to the Catalogue of the Mathematical, Historical, Bibliographical and Miscellaneous Portion of the Celebrated Library of M Guglielmo Libri which gives a remarkably modern sounding argument for studying the history of science in general and the history of mathematics in particular. In it he wrote:-
The collection about to be sold is composed for the most part of books relative to the sciences (more particularly mathematics), and their history, taken in its most extended sense, that is to say, comprising also many works of biography, bibliography, literary history, and even general literature, necessary to shed light on the march of the human mind. ... [I]ndependently of a design for immediate and practical utility, he, who wishes to apply his mind to the study of the progress of human knowledge, ought to propose to himself a problem of a higher order. He ought, in attentively examining the road pursued by inventors, to endeavour to discover, track by track, at least as far as is permitted, their method of arriving at such invention. To neglect the path by which human nature ought to have passed to arrive at such and such a discovery - for example, not to stop at a mathematical theorem, until at the hands of a Lagrange or a Gauss it has received a definitive form - would be to act as a naturalist who attempted only to study insects under the shape of beautiful butterflies, without giving the slightest attention to the caterpillars, to those less perfect larvae which at a later period are to be transformed into those self-same lepidoptera .... What has already been so suitably done for literary history will eventually be carried out, having already been commenced, for the history of sciences. Solely for the reason that there are more persons who read Shakespeare or Dante than there are those who understand Copernicus or Fermat, it becomes manifest why the interest attached to what may be termed "Curiosities of Literature" is more common, and far wider spread, than that which is excited by books, such as form simply an epoch in the history of science.What are we to make of Libri's contributions here when we now know that indeed he was a thief? Munby looks at precisely this question in  and  and reaches the following conclusions:-
So far as we know the notorious Libri, in his two great sales of 1861, was one of the first who set out to draw English collectors' attention to works important in the history of thought. These two sales of books imported from France contain a magnificent series of manuscripts and books by Galileo, Copernicus, Kepler, Cardan, etc., many with long notes pointing out their significance, and we must not allow ourselves to be blinded to the showmanship and originality of Libri's catalogue by his unenviable reputation as a forger and a thief. ... Libri has fallen under a cloud which obscured his very real merits. The immediate financial results of these two sales must have been disappointing, but in them Libri gave an impetus to collecting in the scientific fields ...By 1868 Libri's health began to fail and, unable to return to France, he left England for his native Italy. He spent his last days in Tuscany in a villa in Fiesole.
After his death, Léopold Delisle began a long investigation to settle the question of whether Libri was guilty of the charges on which he was convicted in 1850. He showed with complete certainty that Libri was indeed a thief on a very large scale. In 1888 the French government requested that the precious books and manuscripts which Libri had stolen, and then sold, be made available for them to buy back. Indeed many of the precious documents were returned to France after lengthy negotiations with the English authorities.
The assessment of Libri made shortly after his death, and quoted in , seems to sum up his contribution well:-
Admirable in the salons and incomparably friendly, flexible, with gentle epigrams of sweet humour, elegant flattery, a good writer in both French and Italian, a profound mathematician, geometer, physicist, knowing history through and through, a very analytic and comparative mind ...; more expert than an auctioneer or a bookseller in the science of books, this man had only one misfortune: he was essentially a thief.
Article by: J J O'Connor and E F Robertson