Dear Readers,

As you may have seen elsewhere, in mid February my wife and I suffered the loss of our home in a fire, in the hills of central Massachusetts. The good news is that we got out safely and had no animals in our care at the time. The fire crews were able to contain the fire from spreading, in what turned into a 3-alarm, 5-hour-long ordeal in subzero temperatures; they did amazing work, and no one was injured. The bad news is that all of my physical historical materials and research of 30 years have gone up in smoke. As a result I have decided to suspend this blog for the time being. It will remain online as a resource for those interested in the history of glass and glassmaking in the seventeenth century and beyond. I do intend to resume writing when I can, but for now my time and energy are required in getting us back on our feet.

Friends are providing temporary shelter for us nearby and our intention is to rebuild as soon as possible. To those who have reached out with a steady hand, to those who have opened their wallets, and offered advice in our time of need, we thank you from the bottom of our hearts. In what are already difficult times for all of us, you have made a huge difference in our lives.

Paul Engle
6 March, 2021

Friday, February 28, 2020

The Glassmaker's Salamander

From Michael Maier's 1617 book of emblems.
The salamander was thought to be born of fire.
If one can say that hot-glass workers have a mascot, it is without any doubt the salamander. Since ancient times, this lizard-like, poisonous skinned amphibian was ascribed to exist within fire, even to be born out of the flames. According to legend, its cold body allowed it to survive the heat. To see one in the flames of a furnace was considered good luck, but glassblowers who suddenly disappeared (to work elsewhere) were said to have been "eaten by the salamander." 

Glass work has always been a hot, sweaty, exhausting affair. It is not surprising that after a long day's labor one might honestly think they saw small animals scampering around in the fire. The legend, however, is an ancient one; Aristotle, in his History of Animals reported that salamanders were thought to possess the ability to put out fire with their bodies. They became part of the lore among glassmakers in Venice on Murano and were even spotted in Antonio Neri's Florence. In his autobiography (1558-1567), Florentine artist Benvenuto Cellini offers this recollection:
When I was about five years old my father happened to be in a basement-chamber of our house, where they had been washing, and where a good fire of oak-logs was still burning; he had a viol in his hand, and was playing and singing alone beside the fire. The weather was very cold. Happening to look into the fire, he spied in the middle of those most burning flames a little creature like a lizard, which was sporting in the core of the intensest coals. Becoming instantly aware of what the thing was, he had my sister and me called, and pointing it out to us children, gave me a great box on the ears, which caused me to howl and weep with all my might. Then he pacified me good-humouredly, and spoke as follows: 'My dear little boy, I am not striking you for any wrong that you have done, but only to make you remember that that lizard which you see in the fire is a salamander, a creature which has never been seen before by anyone of whom we have credible information.' So saying he kissed me and gave me some pieces of money.

Incidentally, at the end of Cellini's life, family friend and Church canon  Piero della Stufa was appointed to settle his estate. Among other items, he was entrusted with the manuscript for Cellini's autobiography, from which the above quote is taken. Della Stufa was also the godfather to Antonio Neri's younger brother Vincenzio.
  
(Quotation from: J. Addington Symonds "Benvenuto Cellini's Autobiography" in Harvard Classics v. 31, Charles W. Elliot, ed. (New York: P. F. Collier & Son, 1910), p. 11 (book I, ch. V.))
* This post first appeared here, in a somewhat different form on 19 August 2013.

Wednesday, February 26, 2020

Early Modern Glass Furnace

From "De re metallica" 
Agricola (Georg Bauer) 1556.
In the seventeenth century, glass furnaces represented a pinnacle of technology. True, the ability to achieve the high temperatures required to melt glass had been around for centuries – high enough to melt gold, silver and copper as well. What made the glass furnace remarkable was its refinement. It made efficient use of its hardwood fuel and was able to maintain a controlled, even temperature long before any thermometer could measure it. In fact, in the early seventeenth century, Galileo was only just beginning to use glass bulbs and tubes to measure differences in ambient room temperatures.

In Florence, the construction used was typical of the time throughout Europe, called a "beehive" furnace because its shape resembled the classic elongated dome of a beehive. A double wall, built of fire resistant bricks, provided further insulation, trapping heat inside. Vertically, the furnace was divided into three levels, each forming a wide open chamber. The bottom space was used to build the fire, and had one or two openings to the outside, used to add wood fuel, rake the coals, or shovel out ash. The second, central level was where the pots of glass resided. A central hole or "eye" on the floor directly exposed the fire pit below. The space directly next to the eye was the hottest, and temperature could be further controlled by moving the crucibles farther away or closer to the eye. A number of openings in the wall allowed gaffers access to the glass pots, and at least one larger opening was used to place new crucibles, or rearrange the existing ones. The upper chamber was used to control the draft, and sometimes for annealing. Again, a central hole in the floor of this (top) level allowed exhaust gasses to leave the glass chamber and an opening to one side vented the exhaust.

In his 1612 book, L’Arte Vetraria, Neri is careful to stress that only dry oak or other hardwood should be used because it burns cleanly, and will not deposit ash or creosote in the glass.
The furnace should have dry wood, hard wood of oak because soft wood tinges the furnace and does no good. Stoke it steadily and continuously so that the flame is always clear, and there is never any smoke, which is very important in order to make a beautiful cristallo.
Once a finished piece of glassware is made, it must be allowed to cool slowly, over a period of many hours. This was often accomplished by building a long enclosed horizontal trough that connected to the furnace. A draft opening at the far end allowed heat from the furnace to be drawn in, and finished pieces were placed in a pan at the furnace end and then slowly pulled by a chain further and further down the trough toward the cooler end. This "annealing" process ensured the glass would not develop stresses and crack as it cooled.

Although Neri does not concern himself with the vagaries of furnace construction in the book, it is clear that he did possess considerable knowledge on the subject. Several of his unconventional methods for making pigments for glass involve taking bricks out of the furnace wall to stash chemicals for long term exposure to the heat.
Take small pieces of copper and put them inside the arches of the furnace. In that place, they will be within the walls. Leave them that way until each piece of copper is well calcined, using a simple fire.
While it is true that artisans of the early seventeenth century did not possess the same understanding of nature that we now enjoy, they did have a working knowledge that served them very well. It was backed by a theoretical framework that was quite sophisticated and was consistent with what could be observed and measured at the time. This is no different from our own modern understanding of nature: sophisticated and consistent with what we can observe and measure.

*This post first appeared here 24 January 2014

Monday, February 24, 2020

Neri and the Kabbalah

Kabbalistic Sephiroth Tree,
from Portae Lucis, Paulus Ricius (Trans.)
Augsburg, 1516.
Kabbalah is a form of mysticism practiced within the Jewish tradition. In the early seventeenth century, there was a great deal of interest in Kabbalistic teachings among Catholic alchemists and natural philosophers. It was recognized that Christian alchemy had its roots in Hermetic and earlier Arabic societies, (the word "alchemy" itself is of Arabic origin.) It was thought that the Jewish Kabbalah was yet another branch of the same traditions of relaying secret knowledge by word of mouth. 

In early modern Florence, Italy, there were some interesting connections between the Kabbalah and glassmaker, alchemist and Catholic Priest Antonio Neri. Here is Neri’s own description, of Kabbalah in his 1613 manuscript Discorso: 
Some call it Kabbalah: in ancient times fathers communicated it to their children only by voice, preserving [this knowledge] for posterity, not for history, but as simple tradition. Others finally gave it the name of 'wisdom' [sapienza] because they rightly believed it was impossible, without this art, to know perfectly the nature and the qualities of natural bodies. In order to achieve the end they wanted, which was the perfection of the bodies, they separated the pure from the impure through various chemical operations, which can all be reduced to six principal phases.*
He goes on to describe basic chemical operations that were thought to be fundamental to purifying materials, and ultimately to the production of the Philosopher's Stone. These techniques are the same as practiced in Christian alchemy, and Neri uses them in his glassmaking recipes. Clearly, he had more than a passing knowledge of the subject, and it is interesting to speculate on how he might have come to learn about Jewish alchemical traditions. 

Early seventeenth century Florence contained a city within a city: the Jewish Ghetto. A walled perimeter encircled what is now the Piazza della Republica. This was the mandated home for all of Florence's Jewish population. Each night, entrance gates were closed and locked from the outside. Within the Ghetto, residents were allowed to live and warship freely, even maintaining a Synagogue. In the daytime, the gates were opened, and residents were allowed to go about their business and leave the city with special passes. Among the Ghetto's most prominent residents was the family of alchemist Benedetto Blanis (c.1580-1647.) Blanis served as librarian to Medici prince Don Giovanni. Giovanni maintained an alchemical laboratory in his residence, which was run by Blanis, located only a short distance from where Antonio Neri was living when he first worked at the Casino di San Marco.  

Don Giovanni maintained a close relationship with Neri’s benefactor Don Antonio de' Medici. So close, in fact that when two of  Blanis' relatives were implicated in a gambling scheme, Don Antonio hid them at his residence and then spirited them away, out of Florence, in his own coach until matters cooled off. Furthermore, Blanis came from a family of doctors who must have been known to Neri's father, royal physician to Grand Duke Ferdinando. Antonio Neri was probably a couple of years older than Blanis, if they did not meet through mutual connections with the Medici family, then perhaps they met on the street. The walk for Neri, between his living quarters near Santa Trinita, and the Casino laboratories would have passed around or through the Ghetto, and the walk for Blanis to Don Giovanni's palazzo on Via Parione took him past Neri's front door. The paths of the two men may have crossed, but there is not direct evidence.

Of course, in the absence of hard facts, there are many other possibilities of how Antonio Neri might have become acquainted with Kabbalistic tradition. By taking a look at Blanis and his connections to the Medici family, we can at least see an area of cooperation between Jewish and Christian alchemists in what we might otherwise assume to be an inviolable separation.** 

* “Discorso sopra la Chimica: The Paracelsian Philosophy of Antonio Neri”, M.G. Grazzini / Nuncius 27 (2012), p. 337.
For more on Blanis, see Edward L. Goldberg, The Secret World of Benedetto Blanis. (2011).
** This post first appeared here on 6 January 2014.

Friday, February 21, 2020

Ultramarine Blue

Scrovegni  Chapel, Padua
Frescos and ultramarine ceiling, Giotto 1306.
In his fifteenth century handbook for painters, Cennino Cennini said, "Ultramarine blue is a color illustrious, beautiful and most perfect, beyond all other colors; one could not say anything about it, or do anything with it, that its quality would not still surpass." The ancient Egyptians used ultramarine to decorate the sarcophaguses of their pharos. Later, Marco Polo reported that it was made at a lapis lazuli mine in Afghanistan. Its name alludes to these far-flung origins: ultra-marine = "beyond the sea." Venetians were probably the first in Italy to learn the extraction technique and import the raw lapis. Producing the rich blue pigment from the rock was no simple task; success required an elaborate set of steps. Because of the difficulty, for a time, an ounce of ultramarine was valued more highly than an ounce of pure gold. In the legal contracts drawn up for commissioned paintings, patrons often stipulated exact amounts of the precious material for the artist to use. Beyond its beauty, its presence in a painting signaled the wealth of its owner.

In the last part of his book, L'Arte Vetraria, Antonio Neri presents his recipes for a variety of paints, including one for ultramarine. In glassmaking, drinking goblets adorned with delicate paint-work raised their value and elevated them into the realm of art. Unlike enamels, which fired into the glass, most paint, including ultramarine could not survive the furnace, requiring application only after a piece was finished. The number of different paint and lake recipes in the book indicates Neri's familiarity with the craft. This, combined with his willingness to use other painter’s materials like "smalt" in his glass formulations, hints at a still unknown chapter in the alchemist's life. Perhaps, for a period in Antwerp, he worked directly with fine artists. Here is Neri’s ultramarine:

Take fragments of lapis lazuli, which you can find plentifully in Venice and at low prices. Get fragments that are nicely tinted a pretty celestial color and remove any poorly tinted fragments. Cull the nicely colored fragments into a pot and put it amongst hot coals to calcine. When they are inflamed throw them in fresh water and repeat this twice. Then grind them on a porphyry stone most impalpably to become like sifted grain flour. 
Take equal amounts, three ounces each, of pine pitch, black tar, mastic, new wax and turpentine, add one ounce each, of linseed oil and frankincense. I put these things in a clay bowl to warm on the fire until I see them dissolve and with a stirring rod, I mix and incorporate them thoroughly. This done, I throw them into fresh water, so they will combine into one mass for my needs.  
For every pound of finely powdered lapis lazuli, ground as described above, take ten ounces of the above gum cake. In a bowl over a slow fire, melt the gum, and when it is well-liquified throw into it, little by little, the finely powdered lapis lazuli. Incorporate it thoroughly into the paste with a stirring rod.
Cast the hot incorporated material into a vessel of fresh water and, with hands bathed in linseed oil, form a round cake, proportionately round and tall. You should make one or more other of these cakes from the quantity of the material. Then soak these cakes for fifteen days in a large vessel full of fresh water, changing the water every two days. In a kettle, you should boil clear common water and put the cakes in a well-cleaned, glazed earthen basin. Pour warm water over them and then leave them until the water has cooled. 
Empty out the water and pour new warm water over them. When it has cooled, pour again, replenishing the warmth. Repeat this many times over, so that the cakes unbind from the heat of the water. Now add new warm water and you will see that the water will take on a celestial color. Decant the water into a clean glazed pan, pour new [warm] water over the cake and let it color [the water].
When it is colored, decant it and pass it through a sieve into a glazed basin. Pour warm water over the cake, repeatedly until it is no longer colored. Make sure that the water is not too hot, but only lukewarm because too much heat will cause the blue to darken, hence this warning, which is very important. 
Pass all this colored water through a sieve into the basin. It still has the unctuosity of the gum, so leave it to stand and rest for twenty-four hours; all the color will go to the bottom. Then gently decant off the water with its unctuosity, pour clear water over it and pass it through a fine sieve into a clean basin. 
Pass the fresh water through the sieve with the color stirred-up so that this color still passes through and therefore a great part of the filth and unctuosity will remain in the sieve. Wash the sieve well and with new water again pass the color through. Repeat these steps three times, which ordinarily leaves all the filth on the blue resting in the sieve. Always wash the sieve each time, cleaning it of all contamination. Put the blue in a clean pan. Gently decant off the water and then leave it to dry. You will have a most beautiful ultramarine, as I have made many times in Antwerp. 
The amount per pound of lapis lazuli will vary. It depends on whether the lapis has more or less charge of color and on the beauty of its color. Grind it exceedingly fine on the porphyry stone, as described above and you will succeed beautifully.  
For a quite beautiful and sightly biadetto blue that mimics ultramarine blue, take ordinary blue enamel and grind it exceedingly fine over the porphyry stone, as above. Incorporate it into the gum cake with the dose described above and hold it in digestion in fresh water for fifteen days as with the lapis lazuli. Follow the directions for the lapis lazuli, in all and for all, until the end. These blues are not only useful to painters, but they also serve in order to tint glasses par excellence.

Wednesday, February 19, 2020

Glassware of an Alchemist

Antonio Neri (1598-1600),
"Libro intitulato Il tesoro del mondo" f. 38
In the introduction of L'Arte Vetraria, his 1612 book on glassmaking, Antonio Neri discusses the technical and scientific uses of glass. He rattles off an impressive list of items, many of which are still in everyday use in chemistry and medicine:
Beyond the ease and low cost with which it is made, and the fact that it can be made anywhere, glass is more delicate, clean, and attractive  than any material currently known to the world. It is very useful to the arts of distillation and spagyrics, not to mention indispensable to the preparation of medicines for man that would be nearly impossible to make without glass. Furthermore, many kinds of vessels and instruments are produced with it;   cucurbits,  alembics,  receivers,  pelicans,  lenses, retorts, antenitors,  condenser coils, vials, tiles, pouring-vessels (nasse),  ampules, philosophic eggs  and balls. Countless other types of glass vessels are invented every day to compose and produce elixirs, secret potions, quintessences, salts, sulfurs, vitriols, mercuries, tinctures, elemental separations, all metallic things, and many others that are discovered daily. Also, glass containers are made for aqua fortis and aqua regia, which are so essential for refiners (partitori) and masters of the prince’s mints to purify gold and silver and to bring them to perfection. So many benefits for the service of humanity come from glass, which seem nearly impossible to make without it.
The glass book, as it was published by Neri, did not contain any illustrations. If we hunt around in the alchemical literature and in museums, we can find examples of the apparatus and vessels on his list, but still, we might feel disappointed at not seeing the specific pieces with which our glassmaker was referencing. As it happens, we actually can see a number of these pieces, exactly as Neri experienced them. Over a decade before writing  the glass book, when he was just completing Catholic seminary to become an ordained priest, Antonio Neri wrote a manuscript devoted to "all of alchemy" in which he shows us many of the same glass vessels. Here he lists and shows us (in the illustration, from left to right, top to bottom) a double vase, a urinal (yes, that kind of urinal), a pair of Florence flasks (the Italians now call this a pallone di Kjeldahl), a philosophic egg, another flask which Neri calls a "bozza longa," an alembic (or still-head), a retort, a bottle,  mouth-to-mouth urinals, a receiver (for a still or retort), a saucer, and assorted cups and ampules. Since many of these terms changed from place to place and over time, we can use this chart to get a much better idea of exactly what Neri was doing in his recipes. The use of urinals in his chemistry kit shows simple practicality; these were standard items made by glass factories. If a low-cost, readily available item could be used in the laboratory, so much the better.

Many of the items Neri lists were used in distillation, which was a basic technique of alchemists. A still could be set up in any number of variations, depending on the intended product, which could range from alcoholic spirits to powerful acids and other reagents. The "athanor" was a stove specially engineered to gently heat a large flask, called the "cucurbit," which contained whatever was to be distilled. The apparatus would include an "alembic"; a cap that fits on top of the cucurbit with a snout-like tube running downward from its top. The idea was that volatile ingredients would evaporate inside the cucurbit, rise up, condense in the alembic and run down its snout, to be collected in a "receiver" vessel. Sometimes, for convenience, all three pieces (cucurbit, alembic and receiver) are together referred to as the alembic. The process could be sped up significantly by adding a condenser coil, what Neri calls a "serpentine." As steam built up in the cucurbit, it was routed through its snout to a coiled tube that might be submerged in cold water. This way, the steam would condense more rapidly, sending more liquid to the receiver. Neri uses this method to produce acids in order to dissolve metal pigments for his glass, but the same basic technique is still applied today in producing industrial chemicals, medicines, perfumes and alcoholic drinks such as moonshine, brandy, vodka, rum and whisky. However, in the distillation of alcohol, metal (usually copper) containers are preferred. Neri was often producing chemicals that would react with metal, glass provided a very good solution to this problem but as he discusses at length, great pains must be taken to ensure that the glass vessels do not crack or break when heated or cooled too suddenly.

* This post first appeared here on 27 December 2015.

Monday, February 17, 2020

Golden Yellow Glass

Yellow Neon Chandelier, 1995
Dale Chihuly.
(Columbus, Indiana Visitors Center). 
"Very few people know how to make colors like golden yellow and solid red well. These are difficult and troublesome in the art of glassmaking, since in making them you must stick precisely to the doses, the timing, the details and the materials as prescribed. The smallest error will cause everything to be ruined, and the colors to be irreparably spoiled. Therefore, you must be on guard not to make mistakes. [1]
So says Antonio Neri in his groundbreaking 1612 book of glass recipes, L’Arte Vetraria. Elsewhere he warns in several places not to add “tartar” to any glass destined for yellow pigmentation. Tartar was a common additive to boost the ‘sparkle’ of a glass because it contained a high level of potassium carbonates. These converted to potassium oxide in the melt, which has a higher refractive index than the usual glass flux, sodium oxide. However, his actual glass recipes tend to contradict this advice. 

Neri says of his “fern glass,” which is entirely potassium based:
…This frit can be given a wonderful golden yellow color provided there is no tartar salt within, as described in the caution, because then golden yellow will not emerge. This crystal is given to a golden yellow that is far more beautiful and pleasant than can be achieved in cristallo made with Levantine polverino salt and with this crystal unlike the other, every kind of job can be done. [2]
“Polverino” was a sodium based plant product used in many of Neri’s glass recipes, which he says was derived from the Kali plant grown in the Levant. The plot thickens when, for yellow, he recommends substituting ‘rocchetta’ another soda based Kali derivative. 

His primary recipe for golden yellow is #46, in which he reveals two ingredients responsible for the color, paradoxically, one of them, in direct contradiction to his previous advice, is tartar: “For every 100 pounds of [glass], add 1 pound of tartar from the dregs of red wine. Use large pieces well vitrified naturally in bottles of wine, because the powder is no good. Crush these raw dregs well, and pass them through a fine sieve. For every 1 pound of these dregs, add 1 pound of prepared Piedmont manganese…” [3] To this he adds the advice that “the powder is always given in parts and given [to the frit], not to the fused glass, because then it will not tint.”

He also offers advice to add more or less pigment depending on the intended use of the glass: more for thin items, less for heavier ones. “For larger [thick] spit beads, it is said that at Murano they reduce the dose of [wine] dregs and manganese by nearly half.”

For Neri’s lead glass, he uses a different combination, this time pairing copper sulfate with iron oxide: “Take 16 pounds of cristallo frit and 16 pounds of lead calx. Mix them well and pass them through a sieve. To this material, add 6 ounces of thrice cooked copper, made with flakes of the kettle-smiths [chapter 28], and 2 pennyweight of iron crocus made with vinegar [chapter 17].” He goes on to advise, “If it leans toward greenishness, add a little iron crocus, which will remove the greenishness and will bring out a yellow color of the most beautiful gold.

Yellow is one of several colors that iron oxide can form in glass, and is used frequently in low-fire pottery glazes. In that realm, it has a reputation as a difficult, unstable color, as Neri alludes to in his warnings. But in modern, higher temperature borosilicate glass, iron oxide is relied on for a nice yellow. In modern soda-lime glass, cadmium, titanium or the exotic praseodymium are more likely choices. They produced bright reliable color that is stable at the higher temperatures of modern operations. In lead glass, selenium is the modern favorite for yellow.

[1] Neri 1612, ch. 45.
[2] ibid, ch 5.
[3] ibid, ch 46.

Friday, February 14, 2020

Torricelli and Glass

Evangelista Torricelli
by Lorenzo Lippi, circa 1647
Evangelista Torricelli (1608–1647) is remembered as the inventor of the mercury barometer. Lesser known are a number of significant contributions he made to mathematics, astronomy and physics. There is no direct connection to the Florentine alchemist and glassmaker Antonio Neri—Torricelli was only a boy of six when Neri died—yet there are unmistakable echoes left by Neri that are amplified when we examine Torricelli’s time in Florence.   

In 1632, Torricelli wrote a letter to Galileo, which began a friendship that lasted until the famous astronomer died a decade later. In fact, Galileo invited Torricelli to stay at his house where they spent the last three months of Galileo’s life working together. If Torricelli had not heard of Neri before, perhaps he became acquainted through the copy of his book, L’Arte Vetraria that Galileo had on his bookshelf. Afterward, while preparing to return to Rome, Torricelli was intercepted by the Grand Duke of Tuscany, Ferdinando II de' Medici, who asked him to succeed Galileo as the chair of mathematics at Pisa. He was given a good salary and quarters at the fabulous palace in the center of Florence, that is now called the Medici-Riccardi.  

Historian Mario Gliozzi writes: “Torricelli remained in Florence until his death; these years, the happiest of his life, were filled with the greatest scientific activity. Esteemed for his polished, brilliant, and witty conversation, he soon formed friendships with the outstanding representatives of Florentine culture.” [1]  The ancient palace itself was largely empty in this period, inhabited by a handful of relatives, officials, intellectuals and artists connected with the Grand Ducal court. [2]

Among Torricelli’s companions at the palace were the three sons of Don Antonio de’ Medici, Antonio Neri’s long time benefactor. The boys, Paolo (1616-1656), Giulio (1617-1670) and Antonfrancesco (1618-1659) moved there in 1646. None of the brothers had personally met Neri, as they were all born shortly after his death, but they must have heard plenty about him growing up. As children, they had the run of the Casino di San Marco, the palace where Neri had made glass and pursued the secrets of alchemy. After Neri’s death, their father, Don Antonio spent significant time trying to hunt down Neri’s secret recipe for transmutation. Years later, when Giulio died in 1670, among his possessions were found a box of elixirs and “a booklet, entitled: Material of all the compounds of Priest Antonio Neri; there is a red dustcover, which says ‘experiments.’” [3] The materials were handed over to Jacinto Talducci, the Grand Duke’s chief chemist, and master of the new glassworks established in the Boboli Gardens, a man whom Torricelli depended on for glass. Talducci was also a veteran of the Casino di San Marco Laboratory; according to legend, as a boy he personally witnessed Neri’s transmutation of gold. Curiously, at Giulio’s death he was listed as living on Borgo Pinti in Florence, the same street on which Antonio Neri grew up. Also the same street where Galileo was tutored in  mathematics as a boy -- at the monastery where Neri's family attended church.

While in Florence, Torricelli took a great interest in optics. Again quoting Gliozzi:
[T]here is very good evidence of his technical ability in working telescope lenses, a skill almost certainly acquired during his stay in Florence. By the autumn of 1642 he was already capable of making lenses that were in no way mediocre, although they did not attain the excellence of those made by Francesco Fontana, at that time the most renowned Italian telescope maker. Torricelli had set out to emulate and surpass Fontana. By 1643 he was already able to obtain lenses equal to Fontana’s or perhaps even better, but above all he had come to understand that what is really important for the efficiency of a lens is the perfectly spherical machining of the surface, which he carried out with refined techniques. The efficiency of Torricelli’s lenses was recognized by the grand duke, who in 1644 presented Torricelli with a gold necklace bearing a medal with the motto “Virtutis praemia.” 
The fame of Torricelli’s excellent lenses quickly became widespread and he received many requests, which he fulfilled at a good profit. He attributed the efficiency of telescopes fitted with his lenses to a machining process that was kept secret at the time but was described in certain papers passed at Torricelli’s death to the grand duke, who gave them to Viviani, after which they were lost.
Gliozzi continues to describe that in 1924 one of Torricelli’s lenses was examined optically using the diffraction grating. “It was found to be of exquisite workmanship, so much so that one face was seen to have been machined better than the mirror taken as reference surface, and was constructed with the most advanced technique of the period.”

In addition to precision glass for lenses, Torricelli depended on Talducci and the grand duke’s furnace for scientific glassware; his experiments that demonstrated the measurement of air pressure required glass tubes, sealed at one end, two ‘cubits’ long (about four feet). They needed to be strong enough to be filled with mercury (which is very heavy) without breaking. It took his colleague Mersenne a couple of years (until 1646) to match the Florentines and obtain an acceptable tube from the French glassworks. 

Torricelli worked with former employees of the Casino di San Marco laboratory who knew Neri, he lived with Don Antonio’s three sons and he took a keen interest in glass; it seems impossible for him to be unaware of Neri and the echoes of his work in Florence.

[1] Mario Gliozzi "Torricelli, Evangelista" in Complete Dictionary of Scientific Biography. 2008. Encyclopedia.com.  http://www.encyclopedia.com/doc/1G2-2830904345.html

[2] 1609-1659 - The last inhabitants of Palazzo Medici http://www.palazzo-medici.it/mediateca/en/Scheda_1609-1659_-_Ultimi_abitanti_di_Palazzo_Medici_

[3] Covoni 1892, p. 193.

Wednesday, February 12, 2020

Benjamin Franklin and Glass

Note: This is a shorter version of a piece appearing in the Spring/Summer 2016 issue of the NAGC Bulletin. Many thanks for their permission to share it here. A copy of the complete article is available through interlibrary loan from the numerous public and art museum libraries which subscribe to this journal(including the Rakow Library at The Corning Museum of Glass). The Bulletin can also be obtained directly from its publisher, the National American Glass Club.


Benjamin Franklin and His Gathering of Glassmakers

Benjamin Franklin by Joseph Duplessis, 1778
Benjamin Franklin (1706-1790) became famous in his own lifetime as a printer, author, inventor, statesman, diplomat and scientific investigator. The man gracing the hundred-dollar bill has been celebrated for his work in a formidable range of fields, so perhaps we should not be surprised to learn of one that has largely escaped notice. In fact, there is an extraordinary further chapter to be told. Franklin fostered a lifelong fascination with glass and spent considerable energy in efforts to attract talent from Europe to work in America.

Glass and glassmaking garnered not only Franklin’s own enthusiasm, but also that of his family and friends. He worked closely with artisans on two continents and applied his considerable knowledge of glass to areas ranging from music to optics to electrical experimentation. On his European diplomatic missions, he tirelessly encouraged foreign glass workers to set up shop in the colonies. In the decades before America gained independence, he recognized and promoted the vital importance of glassmaking. Unbeknownst to many, Benjamin Franklin played a sustained and influential role in the formation of the American glassmaking industry. 

His connections to the field were wide ranging; his older, favorite brother, John Franklin, became co-founder of a glass factory in Braintree Massachusetts from the late 1740s to early 1750s. [1] In Philadelphia, Benjamin befriended Thomas Godfrey (1704–1749), a glazier, optician, glass and instrument maker who rented space from Franklin to work on new inventions. Lambert Emerson was another glass related acquaintance and fellow Freemason; an émigré from Dublin who advertised in Franklin’s newspaper The Pennsylvania Gazette as a “looking glass maker at the Sign of the looking Glass in Front Street, Philadelphia.” [2] Franklin’s neighbor, Caspar Wistar, was a German glassmaker from Cologne. He owned the nearby glassworks at Alloway Creek in Salem County, New Jersey, just twenty miles south of Philadelphia. Besides making windows and bottles, Wistar manufactured special “philosophical” glassware for Franklin, used in his electrical investigations. 

But Franklin had much more than a passing familiarity with glassmaking. In 1746, he advised Connecticut businessman Thomas Darling on the particulars of running a glass foundry, referring to Wistar’s New Jersey operation. In his correspondence, Franklin consistently referred to his neighbor’s ‘Wistarburgh Glass Manufactory’ as “our glasshouse,” strongly implying a business relationship with Wistar. He is credited with several of his own glass inventions. Two popular items that particularly employed glass were bifocal spectacles and his musical armonica. 

Over his lifetime, Franklin traveled to Europe four times between 1725-75. In London, Paris and on side excursions throughout Europe, he was in frequent contact with glassmakers and he spent considerable effort encouraging them to immigrate to America. 
He understood the strong potential of a glass industry as an economic driver and as a window to groundbreaking scientific discoveries. Critically, he also understood the value of inviting foreign workers to participate in the American dream. In London, he frequented the Royal Society (of scientific investigators) and was correspondent and houseguest of such luminaries as Joseph Priestly, David Hume and Erasmus Darwin. Glass was a hot topic of discussion in these circles due to the recent development of electrostatic generators and Leyden jars, which all had critical components made of glass. 

Franklin continued his efforts to woo glassmakers to America, but plainly, it was not always easy. In a correspondence of 1771, we see a rare pessimism rear its head. In Philadelphia, Joseph Leacock, a cousin of his wife, partnered with a local tanner to start a glass factory on what is now Richmond Street. They wrote to Franklin in London hoping to find workers, but his reply was not encouraging, “It is always a Difficulty here to meet with good Workmen and sober that are willing to go abroad. I heartily wish you Success in your laudable Undertaking to supply your Country with so useful a Manufacture…” [3] He had already seen a deal fall apart a couple of months earlier. Dutch glassworker Jacob Schaub borrowed money from Franklin to book passage across the Atlantic bound for the Stiegel Glassworks in Lancaster, Pennsylvania. Unfortunately, Schaub then failed to appear for work. [4]

After nearly four decades championing an American glass industry, word seems to have gotten around. Although his responses are not available, glassmakers wrote to Franklin from around Europe. In 1778, he received a letter from French master glassmaker Müller de la Piolotte, who explained his family’s long history in the art, starting with his ancestors in the Black Forest of Germany. The 43-year-old bachelor had worked in Champagny, Burgundy and in the Alsace-Lorrain regions of France. 

By 1783, the war was over; Britain conceded and signed an armistice with the United States. Franklin received official permission to entertain applications from those willing to immigrate to the former colonies to work; the floodgates opened and finally he received the interest among glassmakers that he had sought all along. Among the letters from many diverse tradesmen around Europe, in July he received one from Bremen, Germany. The family of Herman Heyman thanked Franklin for letters of introduction. They asked for the ambassador’s consideration of “a Plan which we lately received from one of our principal Glass Manufacturers in upper Germany, who intend to establish a Glass Manufactory in Nord [sic] America.” [5]

In October, he received a letter from a Paris glassmaker who worked for the famed Brossard family of Normandy. This man, Sutter, had heard rumors that Franklin was looking for master glassmakers to work in Philadelphia. He offered his services and suggested that he could convince several other glass workers to accompany him. [6]

In January of 1784, Franklin again heard from the Heyman family, in Germany, who wrote,
… to inform you that three other Gentlemen with me Considered most Earnestly … to Erect a Glass-Manufactory in some part of the United states, and we Chused Maryland to be the properest Country for it. … One of my three Friends Mr. John Fried Amelong who had the Mánage of a Glass Manufactory here in Germany will go himself in the spring by the first Vessell [sic] over to Baltimore and take the Direction of the intended Establishing Glas[s] Manufactory, he Carries besides him 80 more Families all Experiented to our Purpose in the Vessell for Baltimore [sic]. [7]

In February of 1784, Caquery de Mezancy wrote to Franklin, on behalf of five other French glassworkers. He had come from a well-known glassmaking family and a month earlier, he discussed with Franklin his desire to establish a glassworks in America. Franklin assured him that once there, they would have no trouble finding a partner who would furnish all necessary funds; he also indicated that they would receive free passage on an American ship. [8]

In 1785, Franklin himself boarded one of those ships and returned to America for good. Even into his eighties, as a senior statesman-scientist he was engaged and still thinking about glass. In 1787 his good friend, astronomer and mathematician David Rittenhouse wrote him this note, perhaps about a sample of copper ruby or gold ruby glass, in which the color develops upon reheating, a so-called 'striking glass':
I broke a little bit off the colourless end of the Glass Tube and placed it in the focus of the Burning Glass leaving it there several minutes, but no change was produced in its Colour. After examining it I exposed it again to the collected rays of the Sun without observing the least change in its colour, but touching it with the end of a small splinter of Cedar wood the wood took fire and the Glass immediately became a fire red. [9]
Franklin and Rittenhouse enjoyed a regular Wednesday appointment, when they met with others and talked about their interests. Thomas Jefferson once commented that he would happily trade a week in Paris for a single evening shooting the breeze with Franklin and Rittenhouse at one of their gatherings. [10]

Franklin’s America was driven by the promise of fresh talent flooding in from abroad. In the realm of glassmaking, he spent a lifetime courting workers from foreign lands to settle here and become his trusted friends and neighbors. Perhaps we should end with a light-hearted but poignant piece of advice written in his Poor Richard’s Almanac, in August of 1736 when he was just thirty-years-old, “Don't throw stones at your neighbors, if your own windows are glass.” [11]


ENDNOTES:
 [1] The glass factory in Braintree Massachusetts was founded by Joseph Crell, John Franklin and Peter Etter in the late 1740s. In 1752, others assumed management. See Carla J.Mulford, Benjamin Franklin and the Ends of Empire, Oxford: Oxford Univ. Press, 2015, p. 156. Thanks to Gail Bardhan of the Rakow Research Library of the Corning Museum of Glass for her assistance on this point and many others throughout the article.
[2] The Knight of Glin, James Peill, John Rogers, Paul Mellon Centre for Studies in British Art., et al (2007), Irish Furniture, New Haven: Yale Univ. Press, p. 37. For the Freemason reference, see The Pennsylvania Gazette, June 25, 1741. Franklin was the chapter’s grand master by 1734.
[3] Letter to Joseph Leacock and Robert Towers from BF, London dated 22 Aug 1772. See The Papers of Benjamin Franklin (1959–) New Haven: Yale Univ. Press, v. 19, p. 282. Also, see http://founders.archives.gov/documents/Franklin/01-19-02-0184. 
[4] Henry William Stiegel (1729-83) owned three glasshouses, in Lancaster County Pa. See letter from Richard Bache to Franklin, dated 16 May 1772 (Bache was Franklin’s son-in-law). http://founders.archives.gov/documents/Franklin/01-19-02-0100.
[5] Letter from sons of Herman Heyman, Bremen to BF, Passay, dated 31 July 1783. Op. cit. Papers of BF, v. 40, p. 143.
[6] Letter from Mr. Sutter to BF, Passay, dated 29 October 1783. Op. cit., Papers of BF, v. 41, p. 548.
[7] Letter from Herman Heyman Jr., Bremen to BF, Passay, dated 19 January 1784. Op. cit., Papers of BF, v. 41, p. 489–90.
[8] Op. Cit., Papers of BF, v. 41, p. 552.
[9] Note to Dr. Franklin, from David Rittenhouse, Monday noon [c. 1787]. Op. cit. Papers of BF, (forthcoming).
[10] Kevin Keim, Peter Keim, (2007). A Grand Old Flag, a History of the United States through Its Flags. New York, New York: Dorling Kindersley Ltd. p. 43.


[11] BF (1736), Poor Richard’s Almanack, Philadelphia, August 1736, (v. 2, p. 141), see https://en.wikiquote.org/wiki/Poor_Richard%27s_Almanack.

Monday, February 10, 2020

Hooke's Tears

Glass drops or tears coated in glue,
after detonation, (cross section is left)
from Robert Hooke's
Micrographia 1664, between p. 10, 11.
In 1661, an Italian reprint of Antonio Neri’s book of glassmaking recipes appeared. One year later, an English translation was published in London by physician Christopher Merrett. As an appendix, Merrett included an account of “glass drops” or tears as demonstrated to the Royal Society. These were molten gathers of glass that were allowed to drip into a bucket of cold water and cool. They formed a round, bulbous front end and a tail that trailed off to a thin filament. What made them so fascinating was that the bulbous end can easily endure strong blows with a hammer, but when the thin filament tail is snapped off, the whole piece explodes into a hail of tiny fragments “and in the dark, sparks [flash] at every break of their surface.” [1]

These glass drops became a novelty at royal courts throughout Europe, given a glass furnace they were easy to make, easy to demonstrate, and never failed to amaze observers who had not seen them before. They sparked animated discussion in the many scientific societies that had sprung up; what forces of nature were involved that a piece of glass could resist a hammer yet explode into dust at the loss of its slender tail? 

In the late seventeenth century a Roman publisher by the name of Tinassi [2] regularly issued compilation of noteworthy letters. In his journal’s edition for the year 1672, he published two letters by Geminiano Montanari, a mathematics professor at the university in Bologna, both on the subject of glass drops. In the introduction, he suggests that these curiosities were
Believed to be introduced in Sweden, Holland, then in England, France and Italy; In Paris in the year 1656, many experiments were made at the Academia which met at the home of Mr. Montmor. [3] Many have written of this, among others Monconys [4] in his "Journey to England,” [5] Thomas Hobbes in his Problematica Physica, [6][…] and Christopher Merrett, which in the Latin translation of L’Arte Vetraria of Antonio Neri, [7] is inserted the experiences of the Royal [Society] of England, [and] Mr. Robert Hooke [8] in his Micrographia. [9]
At a time when the concepts of atoms and molecules were still being debated, the glass drops became a nucleus around which a new science developed of mechanical tension and compression. A simple drip of glass caused sharp minds to puzzle and to take a closer look. 

In  Micrographia, Robert Hooke wrote about how he “ground away neer two thirds of the ball, yet would it not fly to pieces, but now and then some small rings of it would snap and fly off, not without a brisk noise and quick motion, leaving the Surface of the drop whence it flew very prettily branched or creased, which was easily discoverable by the Microscope. This drop, after I had thus ground it, without at all impairing the remnant that was not ground away, I caused to fly immediately all into sand upon the nipping off of the very tip of its slender end.”

Hooke continues to describe coating drops in fish glue (isinglass) which was tough enough to hold the piece together when the tail was snapped. “The drop gave a crack like the rest, and gave my hand a pretty brisk impulse: but yet the skin and leather was so strong as to keep the parts from flying out of their former posture and, the skin being transparent, I found that the drop retained exactly its former figure and polish, but was grown perfectly opacious and all over flaw’d, all those flaws lying in the manner of rings, from bottom or blunt end, to the very top or small point.” (See illustration above.)

He discovers that heating the glass drop and then allowing it to cool slowly neutralizes the explosive effect. Finally, he puts it all together: rapid cooling of the surface causes the interior to be compressed like a spring. Snipping the tail, where the skin is thinnest releases all the pent-up energy at once and the piece explodes.


[1] Tinassi 1672, p. 95.
[2] Niccolò Angelo Tinassi, active 1654-1690.
[3] Henri-Louis Habert de Montmor (c. 1600–1679), founded the Montmor Academy, which met at his house in Paris from 1657 until its dissolution in 1664.
[4] Balthasar de Monconys (1611–1665). 
[5] Monconys 1677,  for glass drops see pp. 32, 42 (fig. 4). https://books.google.com/books?id=L0b687oZRVQC
[6] 1662. Problematica Physica (translated in English in 1682 as Seven Philosophical Problems)
[7] This reference is not to Merrett’s 1662 translation of Neri (1612), but to the 1668 or 1669 edition by Frisius in Amsterdam which includes Merret’s annotations.
[8] Robert Hooke (1635–1703). 
[9] Hooke 1664, pp. 33–44.
*This post first appeared here 2 January 2015

Friday, February 7, 2020

Lead Crystal

Roemer type drinking glass c. 1677,
George Ravenscroft.
The entire fourth part of Antonio Neri's 1612 book L'Arte Vetraria is devoted to the preparation of lead glass, a forerunner of what is now commonly known as lead crystal. This section is unique in the book in that it contains the only instance of the author giving direct advice to glass artists themselves:
"To work lead glass into various drinking glasses or other vessels, or even to draw cane for beadmaking, it is necessary to raise the punty [out of the melt], and to make a gather of glass by turning. Take it out, let it cool somewhat and then work it on a well-cleaned marble [marver]. The marble should be somewhat cool, and well bathed with water before use."
He goes on to describe what might be termed a kind of dance with the glass. As with a human partner, gentle patience is required in learning the boundaries of what can and cannot be done. Ultimately, an artist must come to understand the material's behavior and personality in order to result in a great partnership. For the artist who makes unrealistic demands, glass can be a heartbreaker.  
"This sort of glass, lead glass, is so runny that were it not cooled, and taken up by turning [the punty] to wind a gather, it would be impossible to work. It is so runny that it would not even hold onto the punty, because it is as loose as soup. This arises out of [the fact that] the lead calx causes it to become very fluid."
"Namely, gather the glass little by little, allow it to cool, and work it over marble frequently bathed in water. Furthermore, make sure to keep the pot of glass rather calm, and in a place in the furnace where it will not see too much heat, otherwise it will not be possible to work this glass at all."
The formulation of lead crystal as we know it is a relatively recent development. This is a composition of crushed silica (sand or quartz), potash (potassium carbonates) and lead oxide substituting for calcium to stabilize the composition. It is also true that lead has been added to glass since its invention a few thousand years ago. It is not clear that this addition was always intentional, but a Babylonian tablet of 1700 BCE gives a recipe for pottery glaze that explicitly contains lead. At some point, a discovery showed that small amounts of lead and pigment smeared on glass and fired made stained glass paintings possible. The earliest known examples of colored stained glass windows date to 800-820 (San Vicenzo Abbey excavation in Volturno, Italy.)  In medieval Europe, leading up to Antonio Neri's time, lead glass was used in mosaic tesserae and in artificial gems.

Finally, it is worth noting that Neri's childhood church in Florence, Cestello (now called Santa Maria Maddalena dei Pazzi), was then run by Cistercian monks. It was the Cistercian luminary St. Bernard of Clairvaux who, in the twelfth century, built the first church with large windows, urging, "The soul shall seek the light by following the light."

This post first appeared here 15 November 2013.

Wednesday, February 5, 2020

Friar Mauritio

Friar Mauritio,
Treasure of the world, f.19v (detail)
Antonio Neri, (1598-1600).
Shortly after ordination as a priest in the Catholic Church, Antonio Neri wrote a manuscript devoted to alchemy, which he called Treasure of the World (1598-1600). It was completed a couple of years before we find any reference to his glassmaking activities. Among the technical recipes, is one for the philosopher's stone, entitled "Fifth way to make the stone which is very secret." Neri explains that "Friar Mauritio" was a Dominican brother, held prisoner in "The Castle of Naples" by Gilbert Montpensier in the 15th century. There Mauritio learned the secret of transmuting mercury into gold. Ultimately, he was freed from his French captors and went on to use his secret to create great wealth. The recipe was passed down through his family, and ultimately fell into Neri's hands. He presents the full recipe, which takes many pages in the manuscript detailing complex alchemical manipulations.

Some background is in order here. In the year 1494, French King Charles VIII amassed a very large army (twenty-five thousand men), and with encouragement  from the duke of Milan, marched straight down the Italian peninsula with the intention of annexing the Spanish controlled Kingdom of Naples, which encompassed the entire lower portion of Italy. But by the time Charles marched into the capital city, his victory was already threatened; a "League" was forming to oppose him among the states of northern Italy. Charles set up an occupation government, quickly appointed Gilbert Montpensier as viceroy and judiciously headed back toward France, but not before having to fight through the League forces blocking his way. The city of Naples would be held by the French for only three months; the occupation government barely in control. Truth be told, it was not only Friar Mauritio who was confined, but the entire French contingent was more or less sequestered to several fortresses in the area, as they were greatly resented and resisted by the Neapolitan people. Soon the Spanish military was on the scene and systematically routed French forces, reclaiming all of the lost territory.

The most likely location of Mauritio's imprisonment was the foreboding Castel Nuovo, but there are other possibilities, among them Castel Sant'Elmo and Castel dell' Ovo. In the same years that Neri was writing about the Dominican Friar Mauritio's imprisonment, Dominican friar Tommaso Campanella was held and tortured in Naples, under suspicion of heresy and conspiracy against the Spanish rule of his native Calabria. His "heretical" views on astrology and departure from sanctioned Aristotelian doctrine earned him a cell at Castel Sant'Elmo. 


The ancient Castle dell' Ovo or "castle of the egg," is located along the bay of Naples. The name derives from a story about the Roman poet Virgil, who at one time was thought to be a great sorcerer. Supposedly, he had fortified the foundations of the castle with a magic "egg," which he concealed there. Legend warns that if the egg ever were to be disturbed or broken, the entire Castle would self-destruct, and a series of great calamities would befall the city.

The endeavor of history rightly demands strong attention to demonstrable facts. Unfortunately, folklore is often a casualty of that process, because, by its very nature it has little to contribute that can be vigorously verified. The identity of Neri’s Friar Mauritio and, for that matter, the existence of Virgil's egg in the foundations of a Naples castle, in all likelihood, will never be confirmed. But these stories have qualities that solid evidence often does not capture. Regardless of its factual content, folklore tells us about the hopes and fears of the people who repeat it; it is a taste of their culture. Folklore also emphasizes that the way we see history is very different from the way contemporaries saw it. We have no choice but to view events of the past through a lens of the present, just as Neri viewed it through the lens of his time. His view of the events was very much colored by legends about characters like Virgil and Friar Mauritio, but also by the promise of transmutation, and fear of the Inquisition. 

* This post first appeared here on 12 March 2014.

Monday, February 3, 2020

Veins of the Earth

Antonio Neri, "The Mineral Gold"
Neri 1598-1600 (Ferguson 67), f. 5r.
Over a decade before Antonio Neri wrote L’Arte Vetraria, the book on glassmaking for which he would become famous, he wrote an illustrated manuscript on the subject of alchemy. Begun around 1598 and completed in 1600, this is Neri's earliest known work, written very shortly after he was ordained as a Catholic priest. 

The illustrations are divided between technical depictions of chemical apparatus and allegorical images meant to show philosophical relationships within the natural world. Two of Neri's pictures from this latter group, respectively, show veins of gold and silver growing in the earth. The veins are depicted exactly like the arteries of an animal. In both pictures, they radiate out around fiery holes in the ground, what one might presume to be volcanos. Overhead the sun shines down on the gold and the moon over the silver. Further up in the sky, Neri shows the constellations associated with each metal; Leo the lion for gold and Cancer the crab for silver (his rendition looking more like a lobster).

It was no flight of fancy that mined metal and ore deposits were depicted as literal veins. It was widely thought these were living structures, which carried the earth’s nutrients. In one of Neri's final works, his 1613 manuscript Discorso, he explains the ancient theory that gold could occur as immature seed material, left over from the primordial creation. If properly nourished, this seed would mature and grow into the precious metal, and with the appropriate knowledge this natural process could be restarted, or accelerated and the gold could be brought to perfection by artificial means. 

Antonio Neri, "The Mineral Silver"
Neri 1598-1600 (Ferguson 67), f. 6r.
The idea that mined mineral deposits could regenerate naturally, if left to rest, is an ancient concept, one that persisted long past Neri’s era. In 1814, writing about tin mining in "On the Veins of Cornwall," William Phillips complained to the Geological Society of London, that armed with some current scientific knowledge, "nor would many miners […] believe, even to this day, in the regeneration of metals." Phillips quoted from an 1811 survey by
Tonkin, in Carew's survey of Cornwall: "Whether tin doth grow again, and fill up places which have been formerly wrought away, or whether it only seperateth itself from the consumed offal, hath been much controverted, and is not to this day decided." And  "whether—dead lodes—that have not one grain of tin in them—may not hereafter be impregnated,  matured,  and prove a future supply to the country, when the present lodes are exhausted, I think well deserves our highest consideration."  

At base, this is not superstition nor wild speculation, but rather considered judgments of thoughtful men making careful observations. Mines were often attended by acidic or other caustic liquids, either produced naturally or by washing operations, which leached out and dissolved various solubles. These liquids could sometimes dissolve metal out of ore and redeposit it elsewhere. Abandoned mines, it was noticed, could exhibit new crystal growth after a period of years or centuries. Today, the redeposition of minerals is a well accepted phenomenon, however, where it does occur it takes place not on a human time scale, but on a geological one, over millions of years.

*This post first appeared here in a slightly different form on 2 December 2013.