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The great scientist Isaac Newton dabbled in alchemy during the Great Plague of London. He “thought” toad vomit pills might be the cure and his notes on this have survived. Source: Maria Sbytova / Adobe Stock

Isaac Newton, Alchemy and His Toad Vomit Plague Cure

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Sir Isaac Newton was one of the most influential scientists in world history. He is best-known for his three laws of motion, and his law of universal gravitation. Additionally, he made contributions to the fields of optics and mathematics. Less well-known, perhaps, is Newton’s curiosity and interest in alchemy. It seems that one of the results of Newton’s research in this field was a recipe for a toad vomit lozenge that the great scientist believed was capable of warding off the plague. Although Newton himself did not report on the actual effectiveness of this peculiar lozenge, it would be fair to assume that it did not perform as well as Newton had hoped, if it was made in the first place. Nevertheless, to be fair, the understanding of illnesses was different in Newton’s day and it would be some time before scientists finally discovered the actual mechanism that caused the Great Plague of London. It lasted from 1665 to 1666 and was the last major epidemic of the bubonic plague to occur in England.

Portrait of the "young" Isaac Newton (1642-1727) by artist Godfrey Kneller (1646–1723), painted in 1689. (Godfrey Kneller / Public domain)

Sir Isaac Newton Was Born Weak But He Survived!

Sir Isaac Newton was born on 4 January 1643 in Woolsthorpe, in the East Midlands of England. Newton’s father, also named Isaac Newton, was a yeoman, and died three months before his son’s birth. Newton’s mother was Hannah Ayscough. Newton was born as a weak and tiny baby and was not expected to live long. Had Newton died as an infant, the history of the world would have been quite different. 

It seems that Newton had a difficult childhood. Within two years of her husband’s death, Newton’s mother remarried. Consequently, Newton’s mother moved to a neighbouring village with her new husband, a wealthy minister by the name of Barnabas Smith, leaving the young Newton in the care of his grandmother. Newton was separated from his mother for the next nine years of his life, until the death of his stepfather. Newton’s traumatic experience as a child is believed to have resulted in his pronounced psychotic tendencies. Newton acute sense of insecurity and extreme anxiety when his works were published, and his irrational violence when defending his works are speculated to have their roots in his childhood.

In any event, Newton’s mother, after being widowed for a second time, was now in possession of a considerable amount of property. She decided that Newton should be placed in charge of her estates. As it turned out, Newton did a terrible job, as his interests lay in scholarly pursuits. When this was recognised, Newton was sent back to the grammar school in Grantham, where he had previously studied, to prepare for university. In June 1661, Newton began his studies at Trinity College, Cambridge University. Incidentally, Newton was somewhat older than his fellow undergraduates, due to his interrupted education.

During his undergraduate years, he was influenced by the Scientific Revolution, which was popular at the time, though not part of the curriculum. Consequently, he taught himself the new philosophy, the new mathematics, and even made his own findings, though these pursuits were confined to his notebooks, only to be published later on. Newton completed his studies as an undergraduate in April 1665. In the same year, the Great Plague of London began, which forced the university to close.

Two men discovering a dead woman in the street during the Great Plague of London in 1665. Wood engraving by J. Jellicoe after H. Railton. (CC BY 4.0)

In the Great Plague of London, Isaac Newton Was In His 20s

The Great Plague of London was an outbreak of bubonic plague that devastated London. The outbreak is suspected to have begun in the winter of 1664, though it was only in the spring of the following year that the plague started to spread intensely. This was not the first time London was struck by the plague. In 1625, for instance, up to 40000 Londoners were reported to have died from the plague. The Great Plague of London, however, would turn out to be an even greater disaster.

By the 17th century, the plague had already been killing people all over Europe for centuries. The most horrible episode was no doubt the Black Death which occurred during the middle of the 14th century. Victims of the plague exhibited such symptoms as the blackening of the skin in patches, inflamed groin glands (buboes), nausea, and vomiting. Although the Black Death ended after a few years, epidemic outbreaks of the plague, the Great Plague of London being an instance, occurred around Europe in the centuries that followed. 

The origin of the Great Plague of London is traced to St. Giles-in-the-Field, a suburban parish of London that was poor and overcrowded. After spreading to other impoverished and overcrowded areas on the outskirts of the capital, the plague was carried to other parts of the country. According to one story, for instance, in 1665, a box of laundry was brought by a traveller to Eyam, a small village in Derbyshire. Unfortunately, the laundry was infested with plague fleas. 

Although Eyam was badly hit by the plague, it is estimated that things could have been much worse for Derbyshire had it not been for William Mompesson, the rector of the village. Whilst many of the villagers wanted to flee from the village, which would have spread the plague to other parts of the county, Mompesson managed to persuade them to stay, and to isolate themselves. Although up to 80% of the villagers lost their lives to the plague, Mompesson prevented it from spreading to the rest of Derbyshire, thereby indirectly saving many lives.

The Great Fire of London in 1666 painted by Lieve Verschuier (1627–1686). The fire was credited with killing millions of rats that were carrying the plague carrying fleas. (Lieve Verschuier / Public domain)

Popular Belief: The Great Plague of London Ended Naturally

The plague reached its peak in August 1665, when it claimed 31159 victims. Just three months before that, in May, when the plague began to spread, 43 deaths were reported. In the next two months, the number of deaths from the plague was recorded as 6137 and 17036 respectively. In December, however, the death rate fell suddenly. It has been speculated that with the arrival of winter, the fleas carrying the bacteria were killed off. The decline in the numbers of those dying from the plague continued into the beginning of 1666. The Great Plague of London disappeared by the end of 1667, and no one is quite sure why.

It is popularly claimed that the Great Fire of London, which broke out in September 1666, killed millions of rats, thereby putting an end to the plague. The decline of the plague, however, also happened in other English cities. It has also been suggested that quarantine caused the plague to subside, though it has been pointed out that effective quarantine was only established much later, i.e., around 1720. Therefore, it is commonly accepted that the plague ended spontaneously.  

According to historical records, by the time the plague ended, almost 69000 had people succumbed to it. It is suspected, however, that the total number of deaths was much higher, i.e., more than 100000. The total population of England at the time, incidentally, is estimated to have been around 460000.

Believe it or not even super scientist Isaac Newton took an interest in "pseudoscience" with his views on the use of toad vomit to cure the plague. (paseven / Adobe Stock)

In Isaac Newton’s Day Medicine Was A Primitive Concept

Today, it is generally held that the plague is caused by the bacterium Yersinia pestis, which is transmitted to humans  via infected fleas transported by animals, most notoriously, black rats. This long-held view, however, has been questioned in more recent times by scientists and historians, though these are a minority at present.  Yersinia pestiswas only identified towards the end of the 19th century, so Europeans who lived during the Black Death, and even during Newton’s time, had different ideas of what caused the plague, and how to keep it at bay.

Many believed that the plague was caused by “bad air.” Therefore, one of the ways to ward off the plague was to hold a posy of flowers to the nose. This is supposedly the reason why on some ceremonial occasions, judges in England are given such posies to carry as a memory of the Black Death. Others turned to alchemy for treatments. During the time of the Black Death, alchemy was considered as a form of medicine, and widely used by European doctors. Unsurprisingly, the potions and cures made by these alchemists did not cure the sick. Instead, it worsened the condition of those suffering from the plague. 

One of the consequences of this is that the application of alchemy as medicine slowly declined in Europe. Of course, the practice did not die off completely, and one of the men still trying to combat the plague using alchemy was Isaac Newton himself. A proposed alchemical cure for the plague by Newton came to light only last year, when two previously unpublished pages of his “plague manuscript” notes were put on auction by Bonhams.

Isaac Newton’s manuscript notes on reading Jan Baptist van Helmont’s De Peste indicated clearly (though the image writing is hard to read) that he believed toad vomit was a potential cure for the plague. (Bonhams)

Newton’s Notes On A Plague Book Reveal His Alchemy Beliefs

In 1667, having survived the Great Plague of London, Newton returned to Cambridge University, and did some research on the plague. His primary reference, it seems, was  De Peste, a book on the plague written by Jan Baptist van Helmont, a Belgian alchemist and physician. Jan Baptist had first-hand experience of the plague, as he was serving as a physician in Antwerp when the city was struck by the plague in 1605. Apart from synthesising van Helmont’s main ideas and observations about the plague, Newton also provided what he believed was a cure for the plague. Judged by today’s standards, this cure may be described as rather bizarre.

Newton’s proposed cure for the plague involves a toad being hung upside down in a chimney for three days. The toad was ready to be “harvested” when it vomited and died. The toad’s vomit, which Newton describes as containing “earth with various insects in it,” was to be carefully collected on a “dish of yellow wax.” Next, the dead toad was to be ground up into a powder, and its vomit, along with serum, gradually mixed in. This mixture was then placed into several lozenges, which could then be “worn about the affected area.”

Newton claimed that such lozenges “drove away the contagion and drew out the poison.” Fortunately, this “remedy” didn’t require the consumption of the lozenges. For those who did not have that much time to make these lozenges, Newton suggested that wearing amulets of hyacinth, sapphire, and amber would work as well. 

Of course, this was not the only piece of writing Newton did on during the plague period. In fact, Newton was able to achieve much whilst he was “working from home.” Apparently without the guidance of his professors Newton was able to thrive in his pursuit of new knowledge. The year 1666 would later be dubbed as Newton’s  annus mirabilis, or “year of wonders.”

While he was away from Cambridge, Newton continued working on the mathematical problems he had focused on at university. This would become early calculus. Additionally, he conducted experiments with prisms, which would form the basis of his theories on optics. Lastly, the apocryphal story of how Newton was inspired to formulate his theory of gravitation, i.e., the “apple incident,” is also dated to the year 1666.

Portrait of Sir Isaac Newton in his later years by painter James Thornhill (1675–1734), painted in circa 1712. (James Thornhill / Public domain)

When Newton Died His Manuscript Archive Was Passed On

When Newton died in 1727, his massive archive, which included his plague manuscript, was inherited by his niece, Catherine Conduitt, and remained in her family until 1872. The archive was then donated to Trinity College, Cambridge University, by one of Newton’s descendants, Isaac Newton Wallop, the 5th Earl of Portsmouth. The university decided that only Newton’s mathematics and scientific papers were worth keeping. Consequently, his more controversial writing on alchemy, theology, and philosophy were returned to the earl.

In 1936, these remaining papers were sold to private collectors. It seems that the two pages of the manuscript containing Newton’s “toad vomit lozenges” recipe changed hands several times between private collectors before arriving at Bonhams. These two pages were auctioned online by the auction house in June 2020. Considering the current COVID-19 pandemic, it looks like this was the most opportune moment for the sale of these two pages of Newton’s work.         

To conclude, Newton is no doubt a towering figure in post-Renaissance history and chiefly remembered for his contributions to mathematics and the sciences. Nevertheless, there was another side to this great man that has received much less attention from scholars. This suggests that in some ways, Newton was a product of his time, and that some of his ideas about the world, when viewed from the vantage point we enjoy today, may be said to be beyond bizarre.   

Top image: The great scientist Isaac Newton dabbled in alchemy during the Great Plague of London. He “thought” toad vomit pills might be the cure and his notes on this have survived. Source: Maria Sbytova / Adobe Stock

By Wu Mingren 


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Wu Mingren (‘Dhwty’) has a Bachelor of Arts in Ancient History and Archaeology. Although his primary interest is in the ancient civilizations of the Near East, he is also interested in other geographical regions, as well as other time periods.... Read More

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