It is said that Michael Faraday (1791-1867), a genial and pragmatic scientist, but also an able speaker, during a lecture in which he was presenting his great discovery of electromagnetic induction, he was asked: "But what's all this for?".It is also said that he replied, with an implicit reference to the potential of scientific discoveries, with another question:"What's a baby for?";
It was Antonio Pacinotti (1841-1912) some thirty years later who demonstrated the magnitude of the potentiality of Faraday's discovery by being the first, with genial intuition, to come up with the conceptual and practical solution to the problem of the electromagnetic production of currents of practically constant intensity and that of the production of mechanical work using direct current.
For the creation of the ring machine, of which he had demonstrated the reversibility, and for later improvements and applications, Antonio Pacinotti occupies a position of absolute importance not only in the history of physics, but also in that of technology.
Antonio Pacinotti performed a not negligible part of his activity as a scientist and inventor, as well as professor, in Cagliari.
He was appointed Professor of Experimental Physics and Director of the annexed Physics Laboratory of the Royal University of Cagliari with a decree dated 30 March 1873 and remained as a professor in Cagliari up to 31 December 1881.
Before the end of his second scholastic year in Cagliari, Pacinotti, in a letter dated 6 October 1874, asked the Rector, Professor Patrizio Gennari, to spend scholastic year 1874-75 in Pisa to be near his ailing father and help him, as his assistant, in the practical exercises and lessons, being substituted in Cagliari by a substitute to be paid with a part of his salary.The request was granted and, in that year spent in Pisa, Pacinotti, besides teaching hydraulics, worked hard on researching the electricity produced by molecular friction and a new electromagnetic machine with an electromagnetic flywheel which he later built in Cagliari.
In August 1875, his leave of absence having expired, in reply to the invitation to deliver the inaugural address for scholastic year 1875-76, he wrote to the Rector:"I spoke with the Dean of the Technical Institute in Leghorn and, should I apply, there is the possibility for me to obtain the position of Physicist at the Technical Institute with a stipend of 2200 lire and an assignment of 500 lire...Before applying, which would imply my giving up the position in Cagliari, I feel obliged to beg you to help me with your advice".
He then went on:
The decision must certainly have been a hard one to make, one that was accompanied by the bitter delusion of not having received, first at ministerial level and then at local level, the possibility of doing in Pisa what he thought would be most difficult to do in Cagliari.His state of mind concerning this is clearly expressed in a letter to his professor of physics and master, Riccardo Felici, dated 30 September 1875, in which he gave vent to his emotions.
His desire was to set up in Pisa, in the Technological Physics Laboratory, a small workshop for the construction of his machines; but he understood that that would be impossible if the reform giving the University of Pisa the faculty to award diplomas in Civil Engineering was approved, and he urged Professor Felici to do all he could to avoid this.But that reform was approved and came into force in 1876.Then, mentioning the granting of that large assignment to the Physics Laboratory of the Royal University of Cagliari, of which Rector Gennari had informed him, he concluded this venting of his emotions with the consideration that such an assignment, more than in Cagliari, would have been of great help in Pisa in the Technological Physics Laboratory and, to stay there, he was willing to accept "even a secondary position" temporarily.
After the year spent in Pisa, Antonio Pacinotti returned to Cagliari and, on 16 November 1875, he delivered the inaugural address for scholastic year 1875-76 on an "Outline of the history of engines" which is of considerable interest for certain ideas, still up-to-date, in the field of energy sources and the environment.With the extraordinary grant, he purchased teaching equipment and utensils for the workshop, among which a small lathe and a large one of cast iron and iron which cost 500 lire; thus he could go on with the construction of his machines and complete the one with the electromagnetic coil he had begun in Bologna. As we shall see later on, he also built the ones that were exhibited at national and international expositions.