The Prince of Sansevero Experiments and inventions

As an impassioned student of the military art, in 1747 Raimondo di Sangro published a work on infantry exercises, which was appreciated by the main courts in Europe. His interest in the matter was not limited however to theory and strategy. During his life, he did many experiments and created inventions concerning the artillery.

In 1739 the Prince of Sansevero invented an arquebus which could fire, depending on the requirements of the user, using powder or compressed air, even though it had – as Origlia, his contemporary biographer, states – “but a single firing plate and a single hammer, with only one vent”. The surprising weapon, created for di Sangro by Matteo Algaria, was donated to King Charles.

The most ingenious invention for war was presumably a cannon which, compared with other examples of the same type, weighed 190 lb less and had a much longer range. The lightness of the weapon was such that each soldier could easily carry one, if not even two, also on forced marches. The long note to the Lettera Apologetica dedicated to the inventions of the Prince, written in a literary fiction by an anonymous Duchess di S****, states that the cannon was made “of a certain very special component invented by the Author”. The formula of this special alloy was, however, never made known.

The Sundays of July 1770 saw, on the stretch of sea which separates Capo Posillipo from the Ponte della Maddalena, what must have seemed a miracle: a smart carriage, with many horses and a coachman, careering across the waves. This was the last time the Prince of Sansevero was to amaze the Neapolitans and visitors. Shortly afterwards, on 22 March 1771, he died in his palace in Largo San Domenico Maggiore.

In reality, the horses of the carriage – as Pietro d’Onofrj explains in his Extemporised Eulogy to King Charles (1789) – were made of cork, and the unusual craft went fast thanks to a cunning system of paddlewheels, designed by Raimondo di Sangro. In d’Onofrj’s book, the drawing of the sea-going carriage by Francesco Celebrano is engraved in copper by Giuseppe Aloja in a splendid folding illustration. It was Celebrano who, carrying out the Prince’s project, built the carriage, of which di Sangro also kept a model in his apartment.

Here are a number of news reports about these “sea rides” from the «Gazzetta di Napoli» of 24 July 1770: “The Prince of Sansevero having invented, and had built under his direction […] a boat to represent a carriage capable of holding twelve people, which with the simple movement of its four wheels” advanced “more than if it had oars or sails”, offered “to the eyes of the spectators a pleasant composition and a surprising view”. After testing it at Capo Posillipo, “he has wished over the past Sundays to make this public spectators, crossing in it from the said Capo […] as far as the Ponte della Maddalena, so that all could admire […] the steady unvarying movement, and the high speed, with which the device pushed ahead made its way”.

In the anonymous eighteenth-century baedeker, which used to be sold at the entrance to Palazzo Sansevero, are briefly set out the procedures Raimondo di Sangro used to obtain silk and wax from some vegetable species. The Prince showed these strange materials to travellers on the Grand Tour curious to observe the results of his experiments.

The wax, made “without the natural aid of bees”, was obtained “from various common herbs and flowers”, which were boiled in water duly prepared with “a number of salts”. From this process resulted “a kind of oil, which, when collected and boiled again, takes on the consistency of pure wax”. This wax, white in colour, could be worked exactly like bee’s wax.

In 1752, di Sangro made a discovery which could have been – as Giangiuseppe Origlia commented in 1754 – of “great utility […] for society”. He managed to thread the so-called “vegetable silk”, produced into a few woolly purses from a plant called “Apocynum”. Because of the “extreme shortness” of the filaments of this plant, no-one before him had managed to obtain material. They were of such perfection as to “rival those made with common silk”. Using plant silk, the Prince produced also sheets of “paper like that from China”.

The interests of the Prince of Sansevero also extended to medical science. In the underground workshops of his palace, he developed a number of medicines which worked various cures, which seemed veritable “miracles” to all and sundry. Of his ability to “bring to new life those on the point of death, which vulgarly is called resurrecting the deceased”, we find a description in the Lettera Apologetica.

In 1747 he saved Luigi Sanseverino, Prince of Bisignano, from a death which seemed inevitable “to the most skilled Professors”. “The Author began the disparate and difficult work making use of his secret arts, and in the course of a few weeks not only beat and tamed the ferocity of the illness, but returned him to perfect health, even freeing him from some discomfort, which had troubled him in the past”. The same “portentious event” occurred again around three years later in the person of Filippo Garlini, resident in Rome, whose treatment the Prince supervised by letter. “The most renowned Professors of the medical art” gave “shining testimony” to this remarkable recovery.

As in the case of many other inventions of di Sangro’s, the fomulae for the medical remedies he devised are unknown. The cures gave him his “remarkable fame” as a miracle-worker, so much so that even Minister Bernardo Tanucci – despite not having a good opinion of the Prince – had to affirm in a letter of 1752 that the Duke of Miranda, afflicted by a “malign fever” and “furious with the doctors” who were unable to cure him, called in Raimondo di Sangro, “famous for [having] resurrected Bisignano”.

After setting up – as Origlia says in his Istoria dello Studio di Napoli (1753-54) – “a furnace similar to those used by glaziers” and “a chemist’s laboratory with every type of burner”, the Prince of Sansevero dedicated himself night and day to the most varied experiments. Some of these aimed to produce artificial gems and a special way of colouring glass.

He counterfeited various types of “hard stones, such as the blood green jasper, various kinds of agate, and lapis lazuli […] he had the pleasure of faking even precious stones of all types”. They had the same characteristics as real stones, from which they could “in no wise be distinguished”. Not only this. In the brief guide to the wonders of Palazzo Sansevero known as the Short note (1767), there is a reference to “some jewels, which by nature are pale and have little colour”, which the Prince is said to have treated in order to bring out their colour as much as possible (the amethysts took on “the strongest and most beautiful colour you could ever wish for in an amethyst”). Lastly, in 1767, di Sangro made “another curious discovery”, succeeding in “stripping the true lapis lazuli of its blue colour, turning it white”.

His ability to permeate glass with any colour must have seemed equally incredible. The French scientist de Lalande, who saw the results of these experiments, wrote in his travel diary: “The art of coloured glass seemed a long lost secret. The Prince of Sansevero has worked on it with success. He has pieces of white glass, where you can see the different colours, clear and transparent as if the glass had come out of the furnace with those same colours”. De Lalande deemed the procedure simply “perfect”.

Pyrotechnics had interested Raimondo di Sangro since he was a boarder at the Jesuit College in Rome. On this subject, which was very dear to baroque science, as he declared in his Lettera Apologetica, he aimed to publish a treatise, where he would fully reveal what was still “unknown or hidden” regarding the art. However, it was never published.

Di Sangro did not normally limit himself to the theoretical aspect. He designed a number of pyrotechnic theatres, where lighting the fireworks produced the most varied patterns, such as temples, architectural vistas, playing water, and huts. “Equally marvellous – continues the Lettera Apologetica – is the machine he invented for garden scenes, which […] not only makes a simple sound, like others do, but makes a very clear and distinct birdsong, which is created by the fireworks themselves with no other outside help”.

The Prince’s inventiveness also emerged in the broad chromatic range of his fireworks. Giangiuseppe Origlia tells how he produced “turquoise, citrus yellow, the yellow of the orange, white tending towards the colour of milk, the red colour of rubies” and many other colours. And a particularly fine colour was green fire, “which the Prince had invented in 1739”, so beating Count Rutowsky of Dresden, who had created it only four years later, and not in all the shades made by di Sangro, which ranged from sea green to emerald and grass green.

In May 1753, in the «Novelle Letterarie» of Florence, a famous magazine directed by Giovanni Lami, Raimondo di Sangro sent the first of seven letters to Giovanni Giraldi of the Accademia della Crusca. The letters, translated into French, were then put together by the author in a volume addressed to the physicist Jean-Antoine Nollet, member of the Academy of Sciences in Paris. The subject of these papers was a “marvellous discovery” which the Prince of Sansevero had made in November 1752: the perpetual lamp.

While “engaged in a chemical experiment”, he had accidentally found a substance which, once ignited, had continued to burn for more than three months without the slightest “diminution”, i.e. without any reduction in weight. Torn between his desire of seeing his genius recognised by the scientific community and a natural tendency towards reserve and secrecy, di Sangro made it known that the combustible material was partly made from a substance gleaned from the bone of a human cranium (“the bones of the noblest animal on the Earth”), and in part from substances which he was careful not to specify. He underlined that the matter he had discovered was no simple phosphorus, giving off “a beautiful and lively flame”, even though “rather smaller than those made by wax or oil lamps”.

The perpetual light of the Prince of Sansevero was, and still is, much discussed, and the mystery will presumably remain unsolved. It should however be noted that, despite the fact that Raimondo di Sangro’s light – like a lot of his fabulous discoveries – is highly symbolic and intentionally alludes to esoteric meanings, in his letters to Giraldi and Nollet, he sets out a procedure in line with the methods of experimental science of the period, citing respected physicists (such as Hermann Boerhaave and Petrus van Musschenbroek) and referring to theoretical models widely accepted at the time.

The emotion of discovery, a structured hypothesis for an explanation, repetition of the experiments – all this emerges from the letters of the Prince of Sansevero. He wanted two perpetual lamps to illuminate the Veiled Christ, once it had been moved down to the Underground Chamber of the Sansevero Chapel. The Chamber, however, was never finished, and nothing became of the two lamps. In 1756 di Sangro came back to the idea of the “glorious light”. “Since, therefore, it cannot be doubted that this is a true light, similar to our candles or lamps, and has burned three months and some days without any reduction in the material used for fuel, it can rightly be called perpetual, much more so than those imaginary lights which can sometimes be found in the ancient tombs […] and any other light which does not have the same properties as mine, i.e. all the qualities of other natural flames, does not deserve to be called eternal”.

If it had been made known and produced, an invention of the Prince’s which would have been remarkably useful to civil society was certainly the hydraulic device. Perfected as early as 1739, it was the result of his passion for mechanics and hydrostatics since youth.

The device was conceived in such a way that – in the words of its inventor – “with the action of only two devices, similar to two trumpets”, water could be pushed up “to any height” required, and “without the work of any kind of animal”. The device created by di Sangro merited “the applause, and the praise of the most expert in the art”.

In these terms, the Prince of Sansevero explained the possible applications of his “most useful” creation: “using it in countries where river water is lacking, you can make use of other (water) from collected rain for the use in mills and for making cloth or other things, and this can be done, because water itself always runs from top to bottom, and is then pushed up and then back down again”.

In the eighteenth century, the Sansevero Chapel was connected to the Prince’s palace by an overhead passage, containing a little booth housing a great clock with chimes. This wasn’t the only one to be designed by di Sangro. Another clock, perhaps even more spectacular and baroque, was to have been used to embellish the palace courtyard, but there is no evidence that it was ever finished.

The first record of sophisticated machinery comes from the eighteenth-century Short note on what can be seen in the house of the Prince of Sansevero. In a location near the bridge between the di Sangro home and the mausoleum was the “clock device” which, operated by a musician, played “any air” you could wish for on the chimes. The music was played on the bells, placed within a round temple with eight columns, and was audible some miles away. The “chimes” of the Prince of Sansevero were at that time the only ones of their kind in Italy.

Di Sangro himself described the second clock. As well as marking the days of the month and the week, hours and minutes, it showed “the different phases of the moon”, which at night appeared “luminous and clear, wholly true to the real one”, whether it be full, waxing or waning. At midday, allegorical figures would come out of four openings, which, moving in dance step with musical instruments in their mouths, performed “a finely executed march”. In the place of the pendulum, there was the head of a dragon, whose claws rang the hours and the quarters, striking the bells.

He was still a student at the Roman Jesuit College when, in 1729, Raimondo di Sangro made his remarkable debut as an inventor. Having to build, in the courtyard of the College, a stage which would disappear after a theatrical performance to make room for an equestrian display, and after the plans presented by the best engineers in Rome had been examined, the young Prince’s design was chosen, which envisaged the raising and closing of the stage in a very short time.

The machinery – di Sangro recalls – was made up of “winches and wheels unseen by the spectators”. So, “with the help of a few ropes”, the stage withdrew “in a few moments” resting on the façade of the courtyard, which was now completely empty. It was no less than Nicola Michetti, the already famous Engineer of Czar Peter the Great, who preferred the mechanism thought up by the Prince over all the others. The press report of the evening at the Collegio Romano, entitled Votes for the Succession of the Most August House of Austria, also bears witness to the perfect functioning of the “fine mechanical invention”.

According to a short biography dating from the early nineteenth century, di Sangro is said later to have told his intimate friends and his daughter Carlotta that the plan for the stage “had been suggested to him in a dream by a venerable old man calling himself Archimedes”. Whether the dream apparition was real or not, it is plausible that the Prince wanted to show that the brilliant scientist from Syracuse was his model, almost the ideal initiator of his long and varied experiments.

The experiments in palingenesia (regeneration) are without question the most mysterious carried out by the Prince of Sansevero. According to contemporary sources, he was capable of reproducing plants, insects and small animals from their ashes. Di Sangro’s reserve about the methods of the activities, however, was almost absolute.

A record of one of these incredible experiments is provided by Giangiuseppe Origlia, who speaks of a veritable “resurrection of river crabs, which after being burned to ashes produce a large number of insects, and thus from the second daily feed with fresh ox blood, used in a particular way, brand new ones are born”. The astronomer Joseph Jérôme de Lalande, who met the Prince and visited his palace, tells in his memoirs of a journey of a “natural palingenesia of plants and animals, especially with fennel ash, which, according to him, reproduced the plant”.

Indicative of the greatest reserve with which di Sangro kept his secret is the concluding passage of the anonymous Short note on what can be seen in the house of the Prince of Sansevero, where, hinting at the “fine experiments made above all in palingenesia”, it states that to be able to observe them, “you need a certain familiarity with the Prince”.

“With utmost secrecy it was confided to me that the Prince of San Severo has made a certain substance similar to the blood of San Gennaro, and which in accordance with changes in the air appears to have the same effects”. So the Apostolic Nuncio Lucio Gualtieri wrote in a letter of 18 May 1751. Already tarnished by the recent publication of the Lettera Apologetica and his affiliation to Masonry, Raimondo di Sangro’s reputation with the Church was permanently compromised by of this experiment, which seemed to implicitly question the miracle of the liquefaction of the blood of the patron saint of Naples.

In reality, the Prince, as an indefatigable experimenter, meant to check – as his contemporary de Lalande well understood – “a pure hypothesis regarding Physics”, i.e. that a substance could in specific circumstances dissolve and solidify again. This, however, does not imply that he considered that the phenomenon of liquefaction which took place inside the real ampoules with the blood of San Gennaro did so thanks to the same causes and according to the same method as reproduced in the laboratory. In any case, the system devised by the Prince was much more complex than the concise report which the Apostolic Nuncio made on it.

De Lalande notes that “he had a monstrance or display case similar to that of San Gennaro’s built, with two ampoules of the same form, full of an amalgam of gold and mercury mixed with vermillion, the same colour as coagulated blood. To make this amalgam fluid there is in the space around the edge […] a reservoir of fluid mercury with a valve, which, when the case is overturned, opens and lets the mercury enter the ampoule. At this point, the amalgam becomes liquid and imitates liquefaction. But this is a pure hypothesis of physics, suited to explain an effect. It is the mark of a great physicist to want to explain and imitate everything”.

Another eighteenth-century traveller describes the composition of the substance and the experiment in still greater detail, explaining also how liquefaction did not take place mechanically every time the ampoule was turned, but could even be partial, just as happened with the blood of San Gennaro. And, commenting on the ingenious system created by the Prince, concludes: “All I can say is that it worked perfectly”.

“He found a new way to print with a single press, at the same time, any human figure, and flowers, and every other thing in various colours”, reports an eighteenth-century source concerning one of the more incredible inventions of the Prince of Sansevero – the simultaneous printing of more than one colour, a largely unknown typographic technique at the time. Having designed and installed some printing presses in his home in Piazza San Domenico, di Sangro managed to print in polychrome, and in one go, not only figures, but also beautiful characters.“

Among those able to admire his prints and his polychrome printing was also the Frenchman de Lalande, who described them as follows: “the art of printing in several colours is another of the things which the Prince perfected. He showed me what he had printed on paper and white silk, where he had printed a number of flowers in different colours, with one plate and one turn of the press […] I don’t think that the tables made in Paris by M. Gauthier were realised using the same advantageous procedure”.

What everyone can still appreciate is, however, the result of the system with which the Prince succeeded in printing polychrome characters. “The monument of the new surprising invention” – as Lorenzo Giustiniani rightly defined it in his Historical-critical essay on typography in the Kingdom of Naples (1793) – is in fact the title page of the original edition of the Lettera Apologetica, with the characters in black, red, green and orange. It was di Sangro himself who underlined the extraordinariness of his own method, which caused at least as much amazement as the unorthodox contents of his literary masterpiece: “The difficulty of this invention is clear to those expert in the art, and is generally considered insuperable by all; as is the benefit which can come from it”.

As a “famous investigator into the most recondite mysteries of Nature”, Raimondo di Sangro achieved and created an unknown number of discoveries and inventions. Some of them were presented – in different phases of completion – to the scientific community of the time; others were donated to the Sovereign or shown to a number of especially chosen interlocutors, and still others were used in the Sansevero Chapel, and can still be admired (e.g. the mastic used for the cornice and the capitals of the columns, the incredible Floor Labyrinth, the polychrome inlay, the spectacular colours of the vault, the unusual inscription in relief on the Tomb of Raimondo di Sangro and the Anatomical Machines).

His fundamentally esoteric conception of knowledge meant that almost all the “secrets” of his inventions – as Giuseppe Maria Galanti wrote in 1792 – “either died with him, or lie unknown in some corner of his home”. The literary sources and archives give further information on the variety of his experiments. Here follow some of his inventions not yet mentioned or explored in depth in the texts published here.

In the field of the arts, he invented the so-called “colori oloidrici” which had – explains the Short note on what can be seen in the house of the Prince of Sansevero – “the beauty of colour proper to the miniature, but […] the strength of oils”. This technique could be used on any material, unlike the normal miniature, which could only be applied to ivory, parchment, paper or other perishable materials. He was able to colour marble so that the colours penetrated “from layer to layer” and did not remain only on the surface. He made a number of artificial marbles, which he put on show in his palace. Here were also displayed two pictures made from “wools of various colours”, which created special optical effects and were characterised by mezzotints so delicate as to “rival any other oil painting”.

He did various experiments in manufacturing, in chemistry, mechanics and in other areas of research. He produced an above average and differently manufactured porcelain, whose formula was asked for by Ferdinando IV of Vincenzo di Sangro, son of Raimondo, soon after the death of his father. Back in 1748, he had made two different types of completely impermeable cloth. A riding coat sewn with one of these fabrics was given to King Charles by the Prince, and he used it during the winter hunting season. The following year, “he produced the most perfect painted silk cloth which the French call Pekin”. He built an automatic canteen, which served diners with all kinds of food without the need for waiters.

Another example. He invented “his own paper for artillery cartridges, which does not catch fire, nor does it spark, but immediately turns to carbon”. He invented wood and coal which did not produce ash upon combustion. He obtained artificial blood by treating chewed food and dung. He desalinated sea water. This is how the Short note ended: “the Prince made a large number of other fine discoveries, some of which seemed beyond the Natural order”.