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

The Man Who Liked Books Too Much

Broadway Tower, Worcestershire.
The home of Phillipps' Middle Hill Press

In 1612, Antonio Neri published his famous book on glassmaking, L'Arte Vetraria. [1] The venture was bankrolled by Medici prince Don Antonio for whom Neri had worked as an alchemist and glassmaker in 1601 and possibly a couple of years earlier. The printer was Giunti, the venerated Florentine family of typographers who set up their first press in Venice a century and a half earlier. In Neri's era, they operated as the de facto press for the grand dukes in Florence and they are still in business today.

Neri's book was noticed almost immediately; in a 1614 letter addressed to Galileo, Roman Prince Federico Cesi practically begged his astronomer friend to send a copy. [2] Cesi was the founder of the "Accademia dei Lincei" [Society of Lynxes] a group of naturalists who formed an early version of what would later be called 'scientific societies.' The book was tailor made for such groups who were interested in performing their own experiments, however, sales did not exactly catch fire among the public. 

A few decades later, another scientific society was formed in London, with a charter signed by no less than King Charles II. The Royal Society really gave Neri's book a major boost when in 1662; founding member Robert Boyle commissioned Christopher Merrett to translate the work into English. [3] A year earlier, a second edition had been printed in Florence and a year later, another Italian edition appeared in Venice. [4]

From there, the book took off, sprouting multiple new translations in the Netherlands, Germany, France and Spain. There are many interesting stories of how the book spread across Europe; one of the most fascinating deals not with the book itself but with a publisher. Without any doubt, Sir Thomas Phillipps was the most colorful of any of Neri's printers. In 1826, Phillipps' press issued a reprint of Merrett's original English translation, which was by then over a century and a half old. [5]

By the 19th century, L'Arte Vetraria, or "The Art of Glass" as it was dubbed in English, had passed its prime as the bible of glassmakers. As one would expect, methods and technology had matured considerably over the intervening two centuries. Nevertheless, Phillipps recognized its importance. He was also a bit eccentric. As a child, by his sixth birthday, he already owned over a hundred books; his grand ambition was to own one copy of every book ever printed, a quest he carried into adulthood. He was born in Manchester, the product of a clandestine relationship between a textile baron and a woman other than the one to whom his father was married. Nevertheless, he appears to have been well cared for and inherited what Wikipedia reports was a "substantial estate." [6] A fortune that he promptly started to whittle away, spending lavishly on books and manuscripts. He attended University College Oxford and within a few years, he was made a fellow of the above-mentioned Royal Society. 

Depending on where you stand, Phillipps was a classic example of British eccentricity, a brilliant and dedicated preservationist or a completely obsessed crazy-man. Possibly all three. By the end of his life, he had amassed an estimated sixty thousand manuscripts and forty thousand books. At the time it was the largest such private collection in the world. He housed his treasure in a castle that he had built for the purpose, Broadway Tower, in Worcestershire (see photo above). It is said that he would walk into various bookstores and buy the entire stock; his agents around Europe provided a steady stream of new material. Apparently, he himself possessed a sense of humor about his odd obsession, coining the term "vello-maniac" (referring to the vellum bindings common to many books of that period).

The story does have a darker side, albeit with a silver lining. In 1842, Phillipps started collaborating in research with James Halliwell, then an undergraduate at Cambridge studying Shakespeare. Halliwell became romantically involved with Phillipps eldest daughter Harriett, but Phillipps refused consent for them to marry (which they did anyway). Meanwhile, Phillipps had run through the family fortune and started to borrow heavily. He developed paranoia against Halliwell and vowed that he would never gain control of the collection. He entered negotiations to donate the books and manuscripts to the British Library, but his conditions were unpalatable and a deal was never reached. He wanted to stipulate that the order of books should never be reshuffled and that no Roman Catholic, especially his son-in-law, ever be permitted to touch or view the collection. He became so fearful  about Halliwell that he hired 250 men to move the collection, which took two years, at which point the abandoned castle started to fall into ruins. 

In the end, Phillipps died at the age of 79 in 1872. After a court decision, Harriett did inherit her father's collection and Halliwell did gain control. The silver lining is that the two undertook to carefully disperse the collection to some of the most prestigious libraries in Europe. This project took multiple generations to finish. In fact, the final parcel of books from the Phillipps collection sold at auction in 2006, at Christie's.

[1] Neri 1612.
[2] Cesi 1614a, 1614b.
[3] Neri 1662.
[4] Neri 1661, Neri 1663.
[5] Neri 1826.
[6] "Thomas Phillipps" Wikipedia, http://en.wikipedia.org/wiki/Thomas_Phillipps 
* This post first appeared here on 5 Oct 2014.

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

A Reluctant Glassmaker

The Sun, Robert Fludd

from Utriusque Cosmi (1617),v. 2, p. 19.
(alchemical symbol for gold)

Today, Antonio Neri is best known for his 1612 book, L'Arte Vetraria, in which he exposes the secrets of the art of making glass. In publishing his volume, he helped to fuel new discoveries in chemistry and medicine simply by making glass apparatus more available to experimenters. In fact, chemistry and medicine were areas for which he expressed the highest regard. A 1662 translation of his book into English at the behest of Robert Boyle was one of the first acts undertaken by the newly formed Royal Society in London. Neri himself lived for only two years after his book went to press in his native Florence, and he never saw the seeds of his labor come to fruition. If he had lived, he might well be surprised that his legacy is in glassmaking and not in the subjects that he himself held most dear.

In his death at the age of thirty-eight, Neri missed a rapid advancement in our basic understanding of nature. In the space of only a few decades the face of science and medicine would start to change irrevocably. Soon, experimenters were finding new chemical elements and began to map out the periodic table, often with apparatus made of glass. For centuries, the ancient Aristotelian concept of air, earth, water and fire as the basic building blocks of the universe had endured. By the end of the seventeenth century, the inadequacies of the old model were becoming clear. 

But Neri was not privy to any of this. In his time, any cracks in the Aristotelian model were minor. Like his sponsor, Medici prince Don Antonio, Neri was an adherent of new doctrines of the physician Paracelsus, who rebelled against the old system, but was still very much a product of it. First and foremost, Neri thought of himself as an alchemist. While history has not generally been kind to his ilk, a true understanding of early modern science rests on the methods and reasoning developed by alchemists like Neri. 

Although alchemy covered a wide range of activities, it will forever be associated most closely with the mistaken notion that base metals such as lead or iron could be transmuted into gold. Once science had established this idea as specious, the race was on to separate "new science" from the old. It became fashionable to cast alchemists into the mold of charlatans, tricksters and self-deceived fools. While many such characters did exist, Neri was not one of them; his work was based on careful reasoning and experimentation. The final irony is that through the kind of advancements that he himself helped to pioneer, the majority of his life's work has fallen by the wayside. What has endured the test of modern science is his treatise on glassmaking.

As early as the age of twenty, Neri was presenting  transmutation experiments to expert gold refiners. As late as the year before his death he was writing authoritatively and coherently on the subject. To understand how this is possible – to be rational and methodical, and at the same time completely wrong – is to get a sense of the true difficulties involved in science. Based on what he was taught, what he read, and his own experimentation, Neri thought metals and other materials "matured" over time. He thought that more "imperfect" metals like lead and iron were part of a continuum that ended with the "perfect" metal gold. Furthermore, he thought that primordial "seeds of gold" left over from the creation of the earth could be mined and isolated. Like wheat and other plants, given the correct nurturing, and conditions, this seed material could be encouraged to mature into vast quantities of gold. Writing in his 1613 manuscript Discorso, Neri says,

The response is that the chemical art lets the gold proceed from that present and immediate cause, because this is the seed of gold, which acts naturally when art cooperates. The chemist does nothing but extract the seed from gold and apply it to suitable bodies, with which it is united to render the fruit multiplied in the same way that the farmer does. He does not produce the fruit, but provides and prepares the earth and the seed, uniting them in such a way so that they bear fruit.*

Neri thought that ultimately, for gold transmutation to be successful one needed the blessing of the Creator. He documented his process in a heavily coded (and incomprehensible) recipe he called "Donum Dei" (the most precious gift of God). This series of chemical transformations traces to alchemical writings from as early as the fifteenth century. Neri maintained that those who might harm society with this knowledge or wished to profit personally or swindle others would be denied the blessing and therefore be unsuccessful. 

The remarkable thing here is that Neri's understanding of chemistry was supported at every turn by experimentation. His recorded methods, for transforming lesser metals into one-another, were repeatable and stood the test of scrutiny by contemporary experts. In the light of modern chemistry, these transformations depended on subtle physical processes and chemical reactions that would not be understood for another century or more. By performing these experiments under controlled conditions, he was taking the first steps in what would become modern science. Eventually, it would be understood that while chemical compounds can be created and destroyed by various manipulations, individual elements cannot. Today we know that iron, lead and gold were formed in the cores of ancient stars, not too different from our sun. Lighter elements are successively transformed into heavier ones under a star's "nurturing" conditions. While he lived in a period in which he had little chance of getting the particular details correct, in a poetic sense Neri was not far from the truth.

* See Maria Grazia Grazzini, “Discorso sopra la Chimica: The Paracelsian Philosophy of Antonio Neri” Nuncius 27 (2012) 311–367.

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

The Man Who Liked Books Too Much

Broadway Tower, Worcestershire.
The home of Phillipps' Middle Hill Press

In 1612, Antonio Neri published his famous book on glassmaking, L'Arte Vetraria. [1] The venture was bankrolled by Medici prince Don Antonio for whom Neri had worked as an alchemist and glassmaker in 1601 and possibly a couple of years earlier. The printer was Giunti, the venerated Florentine family of typographers who set up their first press in Venice a century and a half earlier. In Neri's era, they operated as the de facto press for the grand dukes in Florence and they are still in business today.

Neri's book was noticed almost immediately; in a 1614 letter addressed to Galileo, Roman Prince Federico Cesi practically begged his astronomer friend to send a copy. [2] Cesi was the founder of the "Accademia dei Lincei" [Society of Lynxes] a group of naturalists who formed an early version of what would later be called 'scientific societies.' The book was tailor made for such groups who were interested in performing their own experiments, however, sales did not exactly catch fire among the public. 

A few decades later, another scientific society was formed in London, with a charter signed by no less than King Charles II. The Royal Society really gave Neri's book a major boost when in 1662; founding member Robert Boyle commissioned Christopher Merrett to translate the work into English. [3] A year earlier, a second edition had been printed in Florence and a year later, another Italian edition appeared in Venice. [4]

From there, the book took off, sprouting multiple new translations in the Netherlands, Germany, France and Spain. There are many interesting stories of how the book spread across Europe; one of the most fascinating deals not with the book itself but with a publisher. Without any doubt, Sir Thomas Phillipps was the most colorful of any of Neri's printers. In 1826, Phillipps' press issued a reprint of Merrett's original English translation, which was by then over a century and a half old. [5]

By the 19th century, L'Arte Vetraria, or "The Art of Glass" as it was dubbed in English, had passed its prime as the bible of glassmakers. As one would expect, methods and technology had matured considerably over the intervening two centuries. Nevertheless, Phillipps recognized its importance. He was also a bit eccentric. As a child, by his sixth birthday, he already owned over a hundred books; his grand ambition was to own one copy of every book ever printed, a quest he carried into adulthood. He was born in Manchester, the product of a clandestine relationship between a textile baron and a woman other than the one to whom his father was married. Nevertheless, he appears to have been well cared for and inherited what Wikipedia reports was a "substantial estate." [6] A fortune that he promptly started to whittle away, spending lavishly on books and manuscripts. He attended University College Oxford and within a few years, he was made a fellow of the above-mentioned Royal Society. 

Depending on where you stand, Phillipps was a classic example of British eccentricity, a brilliant and dedicated preservationist or a completely obsessed crazy-man. Possibly all three. By the end of his life, he had amassed an estimated sixty thousand manuscripts and forty thousand books. At the time it was the largest such private collection in the world. He housed his treasure in a castle that he had built for the purpose, Broadway Tower, in Worcestershire (see photo above). It is said that he would walk into various bookstores and buy the entire stock; his agents around Europe provided a steady stream of new material. Apparently, he himself possessed a sense of humor about his odd obsession, coining the term "vello-maniac" (referring to the vellum bindings common to many books of that period).

The story does have a darker side, albeit with a silver lining. In 1842, Phillipps started collaborating in research with James Halliwell, then an undergraduate at Cambridge studying Shakespeare. Halliwell became romantically involved with Phillipps eldest daughter Harriett, but Phillipps refused consent for them to marry (which they did anyway). Meanwhile, Phillipps had run through the family fortune and started to borrow heavily. He developed paranoia against Halliwell and vowed that he would never gain control of the collection. He entered negotiations to donate the books and manuscripts to the British Library, but his conditions were unpalatable and a deal was never reached. He wanted to stipulate that the order of books should never be reshuffled and that no Roman Catholic, especially his son-in-law, ever be permitted to touch or view the collection. He became so fearful  about Halliwell that he hired 250 men to move the collection, which took two years, at which point the abandoned castle started to fall into ruins. 

In the end, Phillipps died at the age of 79 in 1872. After a court decision, Harriett did inherit her father's collection and Halliwell did gain control. The silver lining is that the two undertook to carefully disperse the collection to some of the most prestigious libraries in Europe. This project took multiple generations to finish. In fact, the final parcel of books from the Phillipps collection sold at auction in 2006, at Christie's.

[1] Neri 1612.
[2] Cesi 1614a, 1614b.
[3] Neri 1662.
[4] Neri 1661, Neri 1663.
[5] Neri 1826.
[6] "Thomas Phillipps" Wikipedia, http://en.wikipedia.org/wiki/Thomas_Phillipps 
* This post first appeared here on 5 Oct 2014.

A Reluctant Glassmaker

The Sun, Robert Fludd

from Utriusque Cosmi (1617),v. 2, p. 19.
(alchemical symbol for gold)

Today, Antonio Neri is best known for his 1612 book, L'Arte Vetraria, in which he exposes the secrets of the art of making glass. In publishing his volume, he helped to fuel new discoveries in chemistry and medicine simply by making glass apparatus more available to experimenters. A 1662 translation of his book into English was one of the first acts undertaken by the newly formed Royal Society in London, at the behest of Robert Boyle. Neri himself lived for only two years after his book went to press, in his native Florence, and never saw the seeds of his labor come to fruition. If he had lived, he might well be surprised that his legacy is in glassmaking, and not in the subjects that he himself held most dear.

In his death at the age of thirty-eight, Neri missed a rapid advancement in our basic understanding of nature. In the space of only a few decades the face of science and medicine would start to change irrevocably. Soon, experimenters were finding new chemical elements and began to map out the periodic table, often with apparatus made of glass. For centuries, the ancient Aristotelian concept of air, earth, water and fire as the basic building blocks of the universe had endured. By the end of the seventeenth century, the inadequacies of the old model were becoming clear. 

But Neri was not privy to any of this. In his time, any cracks in the Aristotelian model were minor. Like his sponsor, Medici prince Don Antonio, Neri was an adherent of new doctrines of the physician Paracelsus, who rebelled against the old system, but was still very much a product of it. First and foremost, Neri thought of himself as an alchemist. While history has not generally been kind to his ilk, a true understanding of early modern science rests on the methods and reasoning developed by alchemists like Neri. 

Although alchemy covered a wide range of activities, it will forever be associated most closely with the mistaken notion that base metals such as lead or iron could be transmuted into gold. Once science had established this idea as specious, the race was on to separate "new science" from the old. It became fashionable to cast alchemists into the mold of charlatans, tricksters and self-deceived fools. While many such characters did exist, Neri was not one of them; his work was based on careful reasoning and experimentation. The final irony is that through the kind of advancements that he himself helped to pioneer, the majority of his life's work has fallen by the wayside. What has endured the test of modern science is his treatise on glassmaking.

As early as the age of twenty, Neri was demonstrating transmutation to expert gold refiners. As late as the year before his death he was writing authoritatively and coherently on the subject. To understand how this is possible – to be rational and methodical, and at the same time completely wrong – is to get a sense of the true difficulties involved in science. Based on what he was taught, what he read, and his own experimentation, Neri thought metals and other materials "matured" over time. He thought that more "imperfect" metals like lead and iron were part of a continuum that ended with the "perfect" metal gold. Furthermore, he thought that primordial "seeds of gold" left over from the creation of the earth could be mined and isolated. Like wheat and other plants, given the correct nurturing, and conditions, this seed material could be encouraged to mature into vast quantities of gold. Writing in his 1613 manuscript Discorso, he says,

The response is that the chemical art lets the gold proceed from that present and immediate cause, because this is the seed of gold, which acts naturally when art cooperates. The chemist does nothing but extract the seed from gold and apply it to suitable bodies, with which it is united to render the fruit multiplied in the same way that the farmer does. He does not produce the fruit, but provides and prepares the earth and the seed, uniting them in such a way so that they bear fruit.*

Neri thought that ultimately, for gold transmutation to be successful one needed the blessing of the Creator. He documented his process in a heavily coded (and incomprehensible) recipe he called "Donum Dei" (the most precious gift of God). This name traces to alchemical writings from as early as the fifteenth century. He maintained that those who might harm society with this knowledge or wished to profit personally or swindle others would be denied the blessing and therefore be unsuccessful. 

The remarkable thing here is that Neri's understanding of chemistry was supported at every turn by experimentation. His recorded methods, for transforming lesser metals into one-another, were repeatable and stood the test of scrutiny by contemporary experts. In the light of modern chemistry, these transformations depended on subtle physical processes and chemical reactions that would not be understood for another century or more. By performing these experiments under controlled conditions, he was taking the first steps in what would become modern science. Eventually, it would be understood that while chemical compounds can be created and destroyed by various manipulations, individual elements cannot. Today we know that iron, lead and gold were formed in the cores of ancient stars, not too different from our sun. Lighter elements are successively transformed into heavier ones under a star's "nurturing" conditions. While he lived in a period in which he had no chance of getting the particular details correct, in a poetic sense Neri was not far from the truth.

* See Maria Grazia Grazzini, “Discorso sopra la Chimica: The Paracelsian Philosophy of Antonio Neri” Nuncius 27 (2012) 311–367.

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

Bibliomaniac

Broadway Tower, Worcestershire.
The home of Phillipps' Middle Hill Press

In 1612, Antonio Neri published his famous book on glassmaking, L'Arte Vetraria. [1] The venture was bankrolled by Medici prince Don Antonio for whom Neri had worked as an alchemist and glassmaker in 1601 and possibly a couple of years earlier. The printer was Giunti, the venerated Florentine family of typographers who set up their first press in Venice a century and a half earlier. In Neri's era, they operated as the de facto press for the grand dukes in Florence and they are still in business today.

Neri's book was noticed almost immediately; in a 1614 letter addressed to Galileo, Roman Prince Federico Cesi practically begged his astronomer friend to send a copy. [2] Cesi was the founder of the "Accademia dei Lincei" [Society of Lynxes] a group of naturalists who formed an early version of what would later be called 'scientific societies.' The book was tailor made for such groups who were interested in performing their own experiments, however, sales did not exactly catch fire among the public. 

A few decades later, another scientific society was formed in London, with a charter signed by no less than King Charles II. The Royal Society really gave Neri's book a major boost when in 1662; founding member Robert Boyle commissioned Christopher Merrett to translate the work into English. [3] A year earlier, a second edition had been printed in Florence and a year later, another Italian edition appeared in Venice. [4]

From there, the book took off, sprouting multiple new translations in the Netherlands, Germany, France and Spain. There are many interesting stories of how the book spread across Europe; one of the most fascinating deals not with the book itself but with a publisher. Without any doubt, Sir Thomas Phillipps was the most colorful of any of Neri's printers. In 1826, Phillipps' press issued a reprint of Merrett's original English translation, which was by then over a century and a half old. [5]

By the 19th century, L'Arte Vetraria, or "The Art of Glass" as it was dubbed in English, had passed its prime as the bible of glassmakers. As one would expect, methods and technology had matured considerably over the intervening two centuries. Nevertheless, Phillipps recognized its importance. He was also a bit eccentric. As a child, by his sixth birthday, he already owned over a hundred books; his grand ambition was to own one copy of every book ever printed, a quest he carried into adulthood. He was born in Manchester, the product of a clandestine relationship between a textile baron and a woman other than the one to whom his father was married. Nevertheless, he appears to have been well cared for and inherited what Wikipedia reports was a "substantial estate." [6] A fortune that he promptly started to whittle away, spending lavishly on books and manuscripts. He attended University College Oxford and within a few years, he was made a fellow of the above-mentioned Royal Society. 

Depending on where you stand, Phillipps was a classic example of British eccentricity, a brilliant and dedicated preservationist or a completely obsessed crazy-man. Possibly all three. By the end of his life, he had amassed an estimated sixty thousand manuscripts and forty thousand books. At the time it was the largest such private collection in the world. He housed his treasure in a castle that he had built for the purpose, Broadway Tower, in Worcestershire (see photo above). It is said that he would walk into various bookstores and buy the entire stock; his agents around Europe provided a steady stream of new material. Apparently, he himself possessed a sense of humor about his odd obsession, coining the term "vello-maniac" (referring to the vellum bindings common to many books of that period).

The story does have a darker side, albeit with a silver lining. In 1842, Phillipps started collaborating in research with James Halliwell, then an undergraduate at Cambridge studying Shakespeare. Halliwell became romantically involved with Phillipps eldest daughter Harriett, but Phillipps refused consent for them to marry (which they did anyway). Meanwhile, Phillipps had run through the family fortune and started to borrow heavily. He developed paranoia against Halliwell and vowed that he would never gain control of the collection. He entered negotiations to donate the books and manuscripts to the British Library, but his conditions were unpalatable and a deal was never reached. He wanted to stipulate that the order of books should never be reshuffled and that no Roman Catholic, especially his son-in-law, ever be permitted to touch or view the collection. He became so fearful  about Halliwell that he hired 250 men to move the collection, which took two years, at which point the abandoned castle started to fall into ruins. 

In the end, Phillipps died at the age of 79 in 1872. After a court decision, Harriett did inherit her father's collection and Halliwell did gain control. The silver lining is that the two undertook to carefully disperse the collection to some of the most prestigious libraries in Europe. This project took multiple generations to finish. In fact, the final parcel of books from the Phillipps collection sold at auction in 2006, at Christie's.

[1] Neri 1612.
[2] Cesi 1614a, 1614b.
[3] Neri 1662.
[4] Neri 1661, Neri 1663.
[5] Neri 1826.
[6] "Thomas Phillipps" Wikipedia, http://en.wikipedia.org/wiki/Thomas_Phillipps 
* This post first appeared here on 5 Oct 2014.

Glass Salt

Diderot, d'Alembert, L'Encyclopédie (1772) Raking Out Roasted Frit

Making glass from raw materials involves several steps. In his 1612 book on glassmaking, L'Arte Vetraria, Antonio Neri breaks the process down into parts so that, "given a bit of experience and practice, as long as you do not purposely foul-up, it will be impossible to fail." Pure white sand, or preferably quartz river stones which Neri calls "tarso" is broken up and pulverized into a fine powder. The initial work can be done by heating the stones in a furnace, then dropping them into a vat of clean cold water, where they will fracture due to the thermal shock. The process was often repeated multiple times. From there, the pieces are pulverized in a stone mortar and pestle. Stone, because metal tools would contaminate the quartz, and in the end tint the glass. Finally, a powder is obtained by grinding with a stone tool on a flat granite "porphyry stone." This powdered quartz is the main ingredient of glass.

The second critical ingredient is the flux, what Neri calls "glass salt" or "soda." This can be obtained from mineral sources, but European glassmakers in the seventeenth century extracted all their salt from certain plants. The powdered quartz was mixed with the salt and a third ingredient, which is critical, lime. Lime is simply calcium oxide used by builders to make cement. It is nothing more than pulverized seashells roasted to a high temperature. Neri advises using two pounds of lime for every hundred pounds of salt. He specifies that it should be added to all his frit recipes, but it is not clear that he understood its critical importance; without lime, the glass would be subject to attack by mere water, eventually decomposing. This mixture of soda, lime and silica when heated in a kiln would chemically react forming "frit." The combined materials were raked around in a kiln for a long period (many hours) and finally formed nut sized pieces. It was cooled and heaped into piles in dry cellars where it was aged for a time. This is where some real "magic" in glassmaking takes place. The glass salt or soda dramatically lowers the melting temperature of the quartz, all the way down to a point that was easily achieved in a wood fired furnace. When a batch of glass was made, the aged frit was then melted in furnace crucibles and skimmed to remove excess salt, which floated on the surface; it could foul the glass, and smelled terrible. The melted glass, now ready to work, was sometimes colored and finally made into objects by gaffers. 

Neri obtained his glass salt from products shipped by traders from the Levant (eastern Mediterranean). It was supplied as the dried, partially charred remains of special plants that grow in arid seaside conditions. Shipping them this way cut down on weight and volume, and prevented rotting. These Soda and Kali plants contain large amounts of sodium carbonates. This is a white powder, chemically identical to what we know as "washing soda." He advises, 

In buying either of these make sure it is richly salted. This may be determined by touching it with the tongue in order to taste its saltiness; but the surest way of all is to do a test in a crucible and to see if it contains much sand or stones, a thing common in this art and very well known by glass conciatori.

He crushes any large pieces of the product in a stone mortar, and sifts the result through a fine screen, ensuring that most of what remains is salt.  

As the common proverb of the art of glassmaking says: a fine sieve and dry wood bring honor to the furnace. Then with any of these sodas, 100 pounds of soda ordinarily requires 85 to 90 pounds of tarso.

Neri sets up large cauldrons of clean water over brickwork stoves, adds the plant product and boils the water. He strains the insoluble parts out and reduces the liquid by evaporation until crystals of the salt start to form on the surface. He skims these off and continues the process. Finally he carefully dries the product. Our glassmaker describes several variations of this process, including one in which he takes extreme measures to ensure the purity of the salt and clarity of the finished glass. In all, this is a task that could easily take several weeks to perform for the amount of frit to fill a single pot for the gaffer to work.

Not content with the established materials, our glassmaker experimented extensively with other plants: 

[U]se the husks and stalks of fava beans after the farmhands have thrashed and shelled them. With the rules and diligence prescribed for the Levantine polverino salt, extract the salt from this ash, which will be marvelous, and from which a frit can be made using well-sifted white tarso, as is described throughout this work. A very noble frit will result, which in the crucible will make a crystal of all beauty. The same may be made from the ashes of cabbages, or a thorn bush that bears small fruit, called the blackberry, even from millet, rush, marsh reeds, and from many other plants that will relinquish their salt. *

*These other plants produce potassium carbonate salts with similar properties to sodium carbonate.

** This post first appeared here 9 December 2013.

The Reluctant Glassmaker

The Sun, Robert Fludd

from Utriusque Cosmi (1617),v. 2, p. 19.
(alchemical symbol for gold)

Today, Antonio Neri is best known for his 1612 book, L'Arte Vetraria, in which he exposes the secrets of the art of making glass. In publishing his volume, he helped to fuel new discoveries in chemistry and medicine simply by making glass apparatus more available to experimenters. A 1662 translation of his book into English was one of the first acts undertaken by the newly formed Royal Society in London, at the behest of Robert Boyle. Neri himself lived for only two years after his book went to press, in his native Florence, and never saw the seeds of his labor come to fruition. If he had lived, he might well be surprised that his legacy is in glassmaking, and not in the subjects that he himself held most dear.

In his death at the age of thirty-eight, Neri missed a rapid advancement in our basic understanding of nature. In the space of only a few decades the face of science and medicine would start to change irrevocably. Soon, experimenters were finding new chemical elements and began to map out the periodic table, often with apparatus made of glass. For centuries, the ancient Aristotelian concept of air, earth, water and fire as the basic building blocks of the universe had endured. By the end of the seventeenth century, the inadequacies of the old model were becoming clear. 

But Neri was not privy to any of this. In his time, any cracks in the Aristotelian model were minor. Like his sponsor, Medici prince Don Antonio, Neri was an adherent of new doctrines of the physician Paracelsus, who rebelled against the old system, but was still very much a product of it. First and foremost, Neri thought of himself as an alchemist. While history has not generally been kind to his ilk, a true understanding of early modern science rests on the methods and reasoning developed by alchemists like Neri. 

Although alchemy covered a wide range of activities, it will forever be associated most closely with the mistaken notion that base metals such as lead or iron could be transmuted into gold. Once science had established this idea as specious, the race was on to separate "new science" from the old. It became fashionable to cast alchemists into the mold of charlatans, tricksters and self-deceived fools. While many such characters did exist, Neri was not one of them; his work was based on careful reasoning and experimentation. The final irony is that through the kind of advancements that he himself helped to pioneer, the majority of his life's work has fallen by the wayside. What has endured the test of modern science is his treatise on glassmaking.

As early as the age of twenty, Neri was demonstrating transmutation to expert gold refiners. As late as the year before his death he was writing authoritatively and coherently on the subject. To understand how this is possible – to be rational and methodical, and at the same time completely wrong – is to get a sense of the true difficulties involved in science. Based on what he was taught, what he read, and his own experimentation, Neri thought metals and other materials "matured" over time. He thought that more "imperfect" metals like lead and iron were part of a continuum that ended with the "perfect" metal gold. Furthermore, he thought that primordial "seeds of gold" left over from the creation of the earth could be mined and isolated. Like wheat and other plants, given the correct nurturing, and conditions, this seed material could be encouraged to mature into vast quantities of gold. Writing in his 1613 manuscript Discorso, he says,

The response is that the chemical art lets the gold proceed from that present and immediate cause, because this is the seed of gold, which acts naturally when art cooperates. The chemist does nothing but extract the seed from gold and apply it to suitable bodies, with which it is united to render the fruit multiplied in the same way that the farmer does. He does not produce the fruit, but provides and prepares the earth and the seed, uniting them in such a way so that they bear fruit.*

Neri thought that ultimately, for gold transmutation to be successful one needed the blessing of the Creator. He documented his process in a heavily coded (and incomprehensible) recipe he called "Donum Dei" (the most precious gift of God). This name traces to alchemical writings from as early as the fifteenth century. He maintained that those who might harm society with this knowledge or wished to profit personally or swindle others would be denied the blessing and therefore be unsuccessful. 

The remarkable thing here is that Neri's understanding of chemistry was supported at every turn by experimentation. His recorded methods, for transforming lesser metals into one-another, were repeatable and stood the test of scrutiny by contemporary experts. In the light of modern chemistry, these transformations depended on subtle physical processes and chemical reactions that would not be understood for another century or more. By performing these experiments under controlled conditions, he was taking the first steps in what would become modern science. Eventually, it would be understood that while chemical compounds can be created and destroyed by various manipulations, individual elements cannot. Today we know that iron, lead and gold were formed in the cores of ancient stars, not too different from our sun. Lighter elements are successively transformed into heavier ones under a star's "nurturing" conditions. While he lived in a period in which he had no chance of getting the particular details correct, in a poetic sense Neri was not far from the truth.

* See Maria Grazia Grazzini, “Discorso sopra la Chimica: The Paracelsian Philosophy of Antonio Neri” Nuncius 27 (2012) 311–367.

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