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Multispectral Imaging of Leonardo da Vinci Drawings

Cerys RJones16 June 2019

In the first year of my PhD, I was asked by Alan Donnithorne, the former head of conservation of prints for the Royal Collection Trust, whether I would be interested in capturing multispectral images of three Leonardo drawings for a book he was writing. Of course I eagerly agreed and in July 2016 Alan brought three beautiful studies by Leonardo to UCL ready for imaging.

The first drawing was the ‘Studies of horses and horses’ heads’ created circa 1481. This is a metalpoint drawing of the portrait of a horse’s head and another in side-profile. To create a metalpoint drawing, a metal-nibbed stylus is used to engrave lines onto paper that has been prepped with glue and ground animal bone, whilst also leaving a deposit of the metal. Although only two horses heads could be seen in visible light, when illuminated in ultraviolet light, two more horses and a dog appeared at the bottom of the page that were invisible to the human eye.

‘Studies of horses and horses’ heads’ illuminated under visible light (left) and after multispectral imaging (right). The two horses and dog at the bottom of the page cannot be seen using the human eye alone. (Image copyright: Queen Elizabeth II, Moral rights: Cerys Jones)

The second drawing was of ‘the anatomy of a bear’s foot’, circa 1488-90. Leonardo initially studied anatomy to inform his paintings;however,this eventually evolved into a plan to write a never-completed treatise on the subject. Martin Clayton, in his 2019 book Leonardo da Vinci: a life in drawing, explained how, at the time, human dissection was illegal and so Leonardo may have been interested in the bear’s foot due to the similarity in the way humans and bears walk. The multispectral imaging of this drawing enabled the different materials (metalpoint, pen and ink, and white heightening) to be separated and show how Leonardo built up his compositions.

The final drawing was a study for ‘the drapery of the Madonna’s arm’ (c. 1510-1515) created for ‘the Madonna and Child with St Anne and a lamb’, a painting currently in the Louvre Museum in Paris. The multispectral imaging revealed the outline of the arm under the drapery,implying that Leonardo first drew a template for the arm and then built the drapery on top of that . The images also enhanced the different materials, including black and red chalk, pen and ink, brush and ink, and white opaque watercolour.

Capturing the multispectral images of the study for ‘the drapery of the Madonna’s arm’. (Image: Cerys Jones)

The full results from this imaging are in Alan’s book Leonardo da Vinci: A Closer Look. This fascinating book investigates many of the Leonardo da Vinci drawings held in the collection at Windsor Library, using a variety of imaging techniques, including multispectral imaging, microscopy, X-Ray fluorescence, and more. He shows Leonardo’s drawings in a way never seen before—including these features invisible to the human eye—to present a detailed view of Leonardo’s musings and thoughtful mind.

The studies for ‘the anatomy of the bear foot’ and ‘the drapery of the Madonna’s arm’ are currently on display in the Queen’s gallery as part of the new exhibition Leonardo da Vinci: a life in drawing to commemorate the 500-year anniversary of Leonardo’s death. This exhibition displays over 200 drawings from Leonardo’s life, spanning a range of topics including anatomy, optics, engineering, botany, cartography and more. I was honoured to be invited to a private view of the exhibition before it was open to the public to celebrate Leonardo’s work and the release of the book. The exhibition is captivating and provides a fascinating insight into Leonardo’s mind, which you can see jumping across subjects on a single piece of paper. I encourage everyone to attend and be inspired by Leonardo’s inquisitive and ingenious mind.

If you’re interested in learning more about my work on the Leonardo drawings, check out my poster!

At the private view of the Leonardo da Vinci: a life in drawing exhibition at the Queens Gallery in Buckingham Palace (Image: Cerys Jones)

Question of the Week: How do dogs recognise other dogs?

Cerys RJones30 April 2019

From Great Danes and Dogue de Bordeauxs to miniature Dachshunds and Chihuahuas, man’s best friend comes in a variety of shapes and sizes, so how can they recognise fellow dogs even when they all look so different?

Dogs come in a variety of different shapes and sizes, featuring Jess the black Labrador, Jewell the miniature Dachshund, Percy the Bichon Frise, Luna the Dogue de Bordeaux, Scratch the Jack Russell Terrier, and Spud the mixed-breed. (Engager’s own photos)

The Kennel Club recognises 211 different breeds of dogs but with different coats and mixed-breeds, there are by no means 211 dog-shaped moulds. Despite this, your dog can decipher between a Bichon Frise and a lamb instantly. This is in part due to their impressive sense of smell which they use to smell the hormones secreted by other dogs. Not only do they have a large nose cavity, which contains a folded surface covered by the sensing organ that is up to 23 times larger than in humans, they also have a vomeronasal organ in the roof of their mouth for detecting smells [1]. This means dogs can smell up to 10,000 times better than humans [1].

Seven domestic dog skulls on display in the Grant Museum (Accession number: Z2909)

Dogs’ ability to recognise different chemicals through their sense of smell has been used by humans to sniff out drugs, explosives and even illnesses such as cancer and diabetes. But is this the only sense dogs rely on to recognise other canines? A study from 2013 tested nine dogs’ ability to correctly identify other dogs from pictures [2]. The dogs were shown two images: one of a dog (from a set of 3000 pictures of different breeds, including mixed-breeds) and one of a non-dog animal, which included cats, cows, rabbits, birds, reptiles and even humans. On command, the dog participant had to correctly distinguish between the images and place their paw on the picture of the dog. All nine dogs successfully chose the images of the dogs over the images of non-dogs the required 10 times out of 12. The study concluded that dogs could “form a visual category of “dog pattern”” ([2] page 647); however, it did not allow the researchers “to determine which dog morphotypes or which species were easier to discriminate” ([2] page 648). As the dogs were successful at distinguishing between dogs and other animals from photographs alone, it is clear that they don’t solely rely on a sense of smell.

Hair curlers with a hunting dog on from the Petrie Museum (Accession number: UC8529)

Although varying highly in appearance, from the colour of their coat to the length of their snout, dogs use both their senses of smell and sight to identify others. Exactly which visual cues are required is still unknown. One thing we know for certain is, regardless of how they look, they’re all good dogs!

 

Bibliography

[1] Miklosi, A., (2018) “The Dog: A Natural History” Ivy Press, Brighton

[2] Autier-Derian, D., Deputte, B.L., Chalvet-Monfray, K., Coulon, M., and Mounier, L., (2013) “Visual discrimination of species in dogs (Canis familiaris)” Anim Cong, 16, pp 637-651.

Simply the Bes: 7 reasons Bes should be your favourite Egyptian god

Cerys RJones6 April 2019

Forget Anubis, Horus and Ra, Bes is the bes(t) Egyptian god around! His figure may not land him any jobs striding down our catwalks (he is short and has a large protruding stomach) but his distinctive and playful face won the hearts of Ancient Egyptians and even spread to the Roman empire, Cyprus, Syria and more. Here are 7 reasons why you should love Bes as much as the Egyptians did:

1) He protects your home
Like our modern day ‘live laugh love’ wall stickers, Ancient Egyptian families often decorated their home with images of Bes. His figure is found on a range of household objects including mirrors, cosmetic jars and even the headboard of beds where he’d protect the person sleeping.

Wooden cosmetic-spoon featuring Bes at the British Museum. Museum number EA5954.

2) He loves music and dancing
If you could only have one Egyptian god at your house party, you’d choose Bes. What better party guest than one who can provide great music and dance all night whilst simultaneously protecting the house? You can see figurines of Bes dancing at the current exhibition in the Petrie Museum called ‘Shake, Rattle and Roll: Sounds of Roman Egypt’. He is often depicted playing a tambourine or harp or dancing near other musicians, and some performers even tattooed his image on their bodies.

Dancing Bes alongside seated group of musicians in the Metropolitan Museum of Art. Accession number: 23.6.79.

3) You can wear him on your jewellery
The collection in the Petrie Museum contains many strings of beads with amulets of Bes, such as the blue faience bead of Bes’ head (read more about the bluefaiencein Arendse’s blogpost.). These were probably worn for protection but make for a great statement piece too.

Amulets of Bes in the Petrie Museum with accession numbers UC37498 (top) and UC38008 (bottom). Engager’s own photo.

4) There are vessels made in the shape of his head
It’s impossible to miss the abundance of pottery vessels in the Petrie Museum featuring Bes’ face. They’re so charming and always popular among the visitors at the museum, featuring heavily on the #PetrieMuseumInstagram hashtag.

Pottery vessel with Bes’ face decoration in the Petrie Museum. Accession number: UC8902. Engager’s own photo.

5) He makes you smile…and he’s supposed to!
When ancient Egyptian babies would unexpectedly laugh or smile, many Egyptians believed that Bes was somewhere in the room pulling funny faces. He was a protector of mothers, children and pregnant women, and wall paintings of Bes have been found in rooms that were associated with children or childbirth.

Column Capital in the form of a Bes-image in the Metropolitan Museum of Art. Accession number: 23.2.35. Engager’s own photo.

6) He had a distinctive style
As can be clearly seen on the amulets, Bes often wore a headdress made of feathers. He also was depicted wearing a lion skin cape, although after the New Kingdom he often opted for a leopard skin cape instead (very on trend!). However, the Romans adopted him as a military deity and often depicted him in their legionary costume.

Bes with a tambourine in the Metropolitan Museum of Art. Accession number: 23.6.16

From the ultimate party guest to splashing his face on vases, Bes is the best Ancient Egyptian god. Initially as a protector of the Pharaoh, Bes became the god of the people, looking after their homes and their children. He was a multifaceted god, who was a serious protector and a merry entertainer. In fact, the only temple believed to have been dedicated to Bes was next to a vineyard so he could protect the grapes and oversee the production of wine! Many relics still exist today featuring his distinctive figure. Visit the Petrie Museum where you can find many Bes related artefacts including several vases, amulets and figurines!

Question of the Week: How do you Describe the Jaw of a Crocodile?

Cerys RJones11 January 2019

Like many of us, Leonardo da Vinci, the great polymath, wrote “to-do” lists. However, in true Leonardo form, his lists did not contain typical mundane tasks such as ‘pick up milk’ or ‘post mum’s birthday card’ but instead provide a fascinating insight into the mind of the Renaissance great. The entries on Leonardo’s list include ‘obtain a skull’, ‘describe the tongue of the woodpecker’ and ‘describe the jaw of a crocodile’. In the spirit of the New Year, with the motivation of completing tasks and resolutions, this blog post aims to tick off one of Leonardo’s 500-year-old objectives.

To start with, let’s return to a previous blog post by UCL museums that discussed the differences between crocodiles and alligators. It includes the location (alligators are typically found in North and South America, whereas crocodiles are typically found everywhere else), how porous the skin is (alligators only have pores around their jaws, whereas crocodiles have them everywhere),  and also the shape of the jaw. The blog post states that the crocodile’s jaw is narrower than the alligators: it is more of a V shape whereas the alligator’s is more rounded at the end, like a U. The jaw is also straighter in an alligator than a crocodile and crocodiles have bottom teeth that extrude from the bottom lip. This is enough information if you are simply looking to identify your crocodiles from your alligators but, for curiosity’s sake, we will continue.

 

The skull of a crocodile. (Grant Museum, X1224)

Walter Isaacson’s biography of Leonardo mentions the inventor’s interest in crocodile jaws. Isaacson states that “a crocodile, unlike any mammal, has a second jaw joint, which spreads out the force when it snaps shut its mouth. That gives the crocodile the most forceful bite of any animal. It can exert 3,700 pounds per square inch of force, which is more than thirty times that of a human bite” [1]. According to Science Daily, crocodiles have likely retained this ability since the Mesozoic Era, when dinosaurs roamed the earth].

A rather humorous experiment involving “ten gigantic crocodiles” was described in an article in Scientific American published February 25th 1882. The aim of the experiment was to calculate the strength of the muscles of the crocodile’s jaw, which they determined as 1540 lb, although noted that “this experiment was performed on a crocodile already weakened by cold and fatigue, its force when in its natural conditions of life must be enormous”. The text also mentions “how difficult it must be to manage such ferocious animals in a laboratory” and measures some of the crocodiles as ten feet long and 154 lb in weight! Leonardo was possibly interested in these creatures for their warfare potential. After all, he was hired as a military engineer and creatively designed weapons and armour.

Sketch of the experiment to determine the power of a crocodile’s jaw in Scientific American (Copyright: Universal History Archives, via Scientific American)

 

Although Leonardo has a bit of a reputation for not finishing his works (look at the Adoration of the Magi, the Battle of Anghiari, and Saint Jerome in the Wilderness to name a few), Leonardo did in fact complete this task. He wrote in one of his notebooks “[the crocodile] is found in the Nile, it has four feet and lives on land and in water. No other terrestrial creature but this is found to have no tongue, and it only bites by moving its upper jaw”. This actually isn’t entirely true. The crocodile does have a tongue – in fact, the female crocodile uses her tongue to help crack the eggshells of her young. There are also many scientific papers that discuss the tongue of a crocodile (for example, see [2]). Furthermore, ‘The British Cyclopaedia of Natural History’ published in 1837 mentions that the crocodile only moving its upper jaw was an “old belief” [3].

Leonardo’s inquisitive mind and thirst for knowledge is reflected on every page of his notebooks. He fills them almost entirely with his fervent list-keeping, avid note-taking, and intricate sketches. The child-like fascination with every aspect of the natural world is a quality that enabled him to become an expert in many areas of studies, including art, anatomy, optics, and geology.

As we enter the New Year, a time for reflections and new beginnings, we could all do with “being more Leonardo” and seeking the answers to life’s curiosities. What unconventional item will you add to your next “to-do” list?

 

References:

[1] Walter Isaacson, Leonardo da Vinci: The Biography (Simon & Schuster, 2017), 398.

[2] J.F. Putterill and J.T .Soley, “General morphology of the oral cavity of the Nile crocodile, Crocodylus niloticus (Laurenti, 1768). II. The tongue,”The Onderstepoort Journal of Veterinary Research71.4 (2004): 263-77.

[3] Charles Frederick Partington, The British Cyclopaedia of Natural History (Orr & Smith, 1835), 550.

Young’s Inequality: The erasure of women’s names in history

Cerys RJones13 December 2018

Young’s Inequality is a powerful result in mathematics, named after William Henry Young, a British mathematician who was president of the London Mathematical Society and a Fellow of the Royal Society. However, I recently learned that much of the work published under William’s name was actually in collaboration with his wife, Grace Chisholm Young.

Grace Chisholm Young studied mathematics at Girton College, Cambridge after being awarded the Sir Francis Goldsmid scholarship. She achieved the equivalent of a first-class degree in her exams, and even decided to take the final year exams for Oxford; she received higher marks than all of the Oxford students and became the first person to achieve a first in any subject from both the University of Oxford and the University of Cambridge. Grace moved to Germany to study for her PhD under the supervision of Felix Klein (famous for the Klein bottle). She subsequently became one of the first women to officially be awarded a doctorate in Germany (read more on Dorothea Schlözer, who received her degree from Gottingen in 1787, and Sofia Kovalevaskaya, who received hers in absentia in 1874).

Klein bottle, first defined by mathematician Felix Klein

After completing her PhD, Grace moved back to the UK and married William, who had been her tutor whilst at the University of Cambridge. William was appointed a professor at several universities whilst Grace cared for their children, studied for a medical degree and simultaneously wrote papers for herself and for William. Grace converted William’s research notes into academic papers, correcting his mistakes and completing his proofs. Their daughter stated that “much of their collaboration was behind the scenes of the very large number of papers published by W. H. Young”. William was aware of the inequality of women at the time and occasionally mentioned Grace’s contributions in footnotes such as one which stated “Various circumstances have prevented me from composing the present paper myself. The substance of it only was given to my wife, who has kindly put it into form. The careful elaboration of the argument is due to her.” Private letters from William to Grace also discussed the nature of their joint work. In 1902, he wrote “The fact is our papers ought to be published under our joint names, but if this were done neither of us get the benefit of it” adding “everything under my name now, and later when the loaves and the fishes are no more procurable in that way, everything or much under your name.”

In time, Grace began to be acknowledged for her work. In 1906, they published a textbook on set theory together and William wrote “any reference to the constant assistance which I have received during my work from my wife is superfluous, since, with the permission of the Syndics of the Press, her name has been associated with mine in the title page.” Grace also began publishing papers in her own name from 1914 and was awarded the Gamble Prize at Gerton College. William, however, received greater recognition for their collaborations and was awarded the de Morgan medal from the London Mathematics Society and the Sylvester prize from the Royal Society. Women were not eligible to become fellows of the Royal Society until 1945, just a year after Grace’s death.

Grace has since received recognition for her many important papers on differentiation and derivatives, as well as for the Denjoy-Saks-Young theorem, which is named after her. Furthermore, in a letter addressed to her sister, Grace wrote “I liked being incog. to the outside world, and felt I had the perfect right to do so, husband and wife being one… I don’t want to be mistaken for the modern ambitious female, ambitious for herself and her own glorification.” Grace never yearned for recognition for herself and may have even disagreed with the message of this blogpost.

Although  there are numerous other stories of women’s successes being hidden under the guise of a man in history, steps are continuously being made towards equality. In 2018, there are 124 women fellows in the Royal Society, although this is only 8.5% of the total number of fellows. According to the Higher Education Staff Statistics for the UK in 2016/17, there are 5050 female professors in the UK (24.6% of the total number of professors in the UK). Whilst these numbers appear to be steadily increasing, there is still a long way to go to see women represented equally in academic positions.

 

The information in this blogpost came from the following papers:

[1] Claire Jones (2000) “Grace Chisholm Young: Gender and mathematics around 1900”, Women’s History Review, 9:4, 675-693

[2] Patricia Rothman (1996) “Grace Chisholm Young and the Division of Laurels”, Notes and Records of the Royal Society of London, 50:1, 89-100

 

Question of the Week: Why does the Kingfisher look blue?

Cerys RJones25 September 2018

The Common Kingfisher is one of Britain’s most colourful native birds and a personal favourite of mine. Despite the name, the Common Kingfisher isn’t actually all that common. I’ve only been lucky enough to see one in the wild and it was a brief encounter; I still vividly remember the bright blue flash of its feathers. Although these creatures are known for their striking colours, the blue feathers down the back of the Kingfisher are actually brown.

The bright blue colour you perceive is due to a phenomenon called structural colouration. Structural  colouration is seen throughout the animal kingdom and makes creatures appear much more colourful than they actually are. So while the coloured pigments in the kingfisher’s feathers are brown, you actually view them as a brilliant blue.


The brightly coloured Common Kingfisher (Image: Avijan saha)

Structural colouration, first described by Robert Hooke and Isaac Newton, is when the observed colour of an object is not due to the pigment but rather caused by some interference effects instead. The structure of the object itself causes a different colour to be perceived than what would typically be observed by the pigment. Structural colouration can result in iridescent colours – i.e. colours that are dependent on the viewing angle – or non-iridescent colours, when the colour remains constant regardless of the viewing angle. Examples of iridescent colours are the feathers of a peacock, which are also pigmented brown but appear blue due to the structural colouration, and the setea (or spines) of the sea mouse. The nanostructures of the setea of the sea mouse and peacock feathers are regular and so reflect the light in the same direction. This means that the bright colour is only perceived at a certain angle.

The setea of the sea mouse appear red, green and blue to act as a warning to potential predators. The sea mice in the Grant Museum are some of my favourite specimens in the museum and are often unfortunately overlooked by visitors. Their interesting name likely derives from the fact that they look like drowned mice when washed up on shore, but their Latin name, Aphrodita, comes from the Ancient Greek goddess of love, Aphrodite, supposedly due to their resemblance to female anatomy…

The Sea Mouse specimen in the Grant Museum, G15 (Author’s own photo)

In contrast, the kingfisher’s feathers are an example of non-iridescent structural colouration. The blue stripe appears blue regardless of the angle of the viewer. This is because the structures are randomly oriented and so the reflections of the light are not angled in the same direction. The blue-and-yellow macaw similarly displays bright blue feathers that are due to non-iridescent structural coloration. These feathers also contain the brown-black pigment melanin that is present in those of the kingfisher.

Let that be a lesson that you can never trust your eyes – at least, not when it comes to structural colouration! Next time you visit the Grant Museum, look out for our kingfisher taxidermy specimen, the sea mice and any other brightly coloured creatures that may be cleverly appearing more colourful than their pigments might suggest!

To read more about this phenomenon, check out this paper.

The Invisible Glow of Egyptian Blue

Cerys RJones20 July 2018

If you were to visit the Petrie Museum with infrared vision, you would probably be drawn to wildly different parts of the collection than you would normally. Certain artefacts would appear to glow before your eyes. This is because of the inventively-named pigment Egyptian blue, which, as the name tells you, is a blue pigment that was commonly used in Egypt. However, Egyptian blue has a special property that makes it stand out from the rest: when illuminated in visible light, it fluoresces infrared light. If you could see infrared light, you would see all of the artefacts that contain this pigment glowing. I haven’t yet evolved to have this special power, but I have a camera that does. This is a multispectral imaging system and is what my PhD research is focused on. Multispectral imaging involves capturing images of objects that are illuminated in ultraviolet, visible and infrared light to reveal features that cannot be detected by the human eye alone.

Last November, I captured multispectral images of this Egyptian mummy mask from the Petrie Museum. In the Petrie catalogue, it is described as a “linen-based cartonnage mask, painted with blue headcloth, white face, black brows, eye-borders and pupils, and red-edged yellow band around face.” This mummy mask would have placed over the mummified body to protect the deceased in the afterlife. The Petrie has several mummy masks in the collection, including some that are gilded with gold.

Late period cartonnage mask (Petrie Museum, 55084)

The mask was illuminated in visible light and an infrared filter was placed in front of the camera lens. This meant that only infrared light was able to pass through the lens and be captured by the camera. The resulting image is below. The blue headcloth appears brightly in the image, indicating that it is painted in Egyptian blue. We were also able to confirm that the little fragment of mask in the vial was also from the headpiece, as this also fluoresced.

The cartonnage mask illuminated in visible light (left) and captured with an infrared filter (right). (Photo: Cerys Jones)

When you search Egyptian blue in the Petrie catalogue, 194 results appear ranging from Egyptian blue scarab beetles to plaster with hieroglyphs written in Egyptian blue paint. Two of my favourite items from the collection are the Egyptian blue hippopotamus and the Egyptian blue paste amulet of a lion-headed goddess. The hippopotamus represents Taweret, the Ancient Egyptian goddess of childbirth and fertility. The lion-headed goddess is probably Bastet, the goddess of warfare in Lower Egypt .

Left, hippopotamus in Egyptian blue pigment (Petrie Museum, 6489) and right, Egyptian blue paste lion-headed amulet (Petrie Museum, 52875).

Next time you visit an Egyptian museum, keep your eyes out for any artefacts that are painted in Egyptian Blue that are glowing unbeknown to your eyes!