In the mid- to late-19th century, science gripped the public imagination. Literacy rates were rising, feeding demand for books. Theories, put forward in books like Charles Darwin's Origin of Species, about how the natural world came to be fascinated readers. Museums and exhibitions promoted interest in science and devices like the microscope. Microscopes became cheaper, and a popular form of entertainment. Viewers peered through them at specimens they'd collected themselves or slides prepared professionally. The image above shows an ocean-dwelling diatom — a single-celled alga surrounded by a glass-like cell wall.
The microscope slide containing the diatom indicates it was collected in Maryland and made by someone identified only as "FM," according to the slide's owner Howard Lynk, an antique slide collector who displays some of his collection on his website, Victorian Microscope Slides. He owns hundreds of slides from the 1830s to around the end of the century. A few are displayed within this gallery.
To the naked eye, this sample looks like what it is, a sliver of bone from a porpoise's vertebrae. But, techniques commonly employed by Victorian microscopists, transform it.
Special filters used in the microscope transform the pale porpoise bone into the vibrant colors seen above. Polarizing filters eliminate certain wavelengths of light based on the direction in which they vibrate, and, when positioned correctly, they reveal special properties of the specimen, related to how the substance refracts, or bends, the light waves that enter it. This produces what's known as interference colors. An additional filter, made of the mineral selenite, further alters the behavior of light and changes the colors that the viewer sees.
Like the porpoise bone, the ammonia sulfate crystals on this slide don't look like much to the naked eye.
But crossed polarizing filters (called a Polariscope) reveal an entirely different sight.
A slide mounter and optician J.B. Dancer perfected the process for miniaturizing photos for microscope slides in the early 1850s. These slides depicted famous people, art, buildings, landmarks and, as shown above, the moon. This slide's maker is known only as 'E.M.'
A revolution in visual communication took place in the 19th century. Images — like book illustrations, panoramas and illusions — became more plentiful and popular. New technologies explored how we see, like the stereoscope, which recreates three-dimensional vision, and sights once available to only a few, like the view through a microscope or telescope, became widely available. Photography was invented in the first part of the century, then applied more to scientific subjects as time progressed, and the scientific study of the eye became important, according to Bernard Lightman, a professor of humanities at York University in Canada and author of the book Victorian Popularizers of Science (University Of Chicago Press, 2010). "People start to think more about the process of seeing, and what does that tell us about the natural world," Lightman said.
In 1839, the Microscopical Society of London recommended two standard sizes for glass slides, and these quickly caught on. In earlier times, specimens were often mounted on sliders made of bone, ivory and hardwood. The sliders shown above are made of mahogany and shown with the viewer used to magnify them.
This microscope was manufactured in 1856 by Smith & Beck, London. Up until the 1850s, a microscope was an instrument only the wealthy could afford. Around 1850, there was a concerted effort to manufacture a useful but relatively inexpensive microscope. Many people at the time believed that educating the general population would bring a greater appreciation of "God's Creation", and thus a more positive and beneficial society. The model shown above was one affordable for the burgeoning middle class, according to Lynk.
Some slides, like the one above, reflected scientific developments of the time. Around the mid- to late-1850s, techniques were developed to dye specific structures within a preserved sample of once-living tissue. Similar approaches are still used today. Developed about the same time, a device called a microtome made it possible to cut much thinner sections of a specimen. Above, an ornately covered slide containing a section of human tongue.
Red dye fills the tiny blood vessels of this tongue tissue. The large, roundish structure in the center of image is a projection on the surface of the tongue known as a fungiform papilla. These projections hold the taste buds, which are not visible in this image. The feather-like projections to the side are filiform papillae.
Ferns were another fad among Victorians. The craze was called "Pteridomania" or Fern Fever. Above, a Victorian-era fern leaf under a microscope. The slide gives no specific information about this fern, although its maker, J.W. Bond, was one of the pioneering early slide mounters, according to Lynk.
Slide makers first used decorative paper covers on microscope slides — like the green and gold cover on this fern specimen — to hold the cover slip in place on the slide. Over time, the covers became more decorative, with patterns unique to their makers.
Slide makers prepared insects like these by using potassium hydroxide to remove their innards, while leaving the hard outer shell, called an exoskeleton, intact. These remains were imbedded in Canadian balsam, which is basically tree sap. Later slide mounters devised a way to preserve the entire insect, including its innards by mounting it within a well on the slide, according to Lynk.
A closer look at a preserved moth larva, mounted by Frederic Enock, a prominent maker of insect slides.
Some slides allowed their makers the opportunity to show off their skills by carefully selecting tiny elements and composing them into images or geometric designs. The arrangement above contains brightly colored butterfly scales, circular diatoms and bits from a type of sea cucumber.
The circular pattern of the arrangement within this slide is visible to the naked eye. Mounters assembled these types of slide while looking through a microscope with help from tools, such as boar bristles and cat's whiskers, according to Lynk.
This arrangement is made up of the tiny hard structures found inside sponges. Called spicules, these are a sponge's structural elements, not unlike bones in a skeleton.
This slide, shown both front and back, contains beard hairs taken from Thomas Beaufort, who died roughly four centuries before the slide was made. Lynk's research revealed that Beaufort was half-brother to King Henry IV and was made Duke of Exeter in 1410. He died in 1427, and was buried at a church in the town of Bury St. Edmund's in England, according to West Suffolk, a book about the history of the western division of the county, published in 1907. On Feb. 20, 1772, laborers found Beaufort's lead coffin and sold it for 15 shillings. His body, which had been embalmed and was perfectly preserved, according to the book, was mutilated — with his arms cut off at the elbows and skull sawed to pieces before he was reburied.
The maker of this slide, C.M. Topping, had connections to the Royal College of Surgeons, where some of Beaufort's body parts were reportedly preserved.
Victorians were also fascinated by Egyptian mummies. They were collected avidly and even unwrapped at events. Not surprisingly, mummies also found their way under the microscope. These slides contain, from left to right, a thin slice of mummy bone, a piece of cloth from a mummy, a slice of wood from a mummy's coffin and a fragment of an Egyptian pyramid.
A view through the microscope showing wood from a mummy's coffin. Slides like these may seem bizarre, but they are most likely authentic, according to Lynk. Recognized slide mounters of the era made slides for the academic and medical community as well as for the public, and had personal connections to museums and societies that would have given them access to unusual specimens. "All of my research would suggest that there was very little, if any, fraud of that kind," he wrote to LiveScience in an email.