Wilson Alwyn “Snowflake” Bentley is one of the first known photographers of snowflakes. He perfected a process of catching flakes on black velvet in such a way that their images could be captured before they either melted or sublimated.
Kenneth G. Lebbrecht notes that the technique used by Bentley to photograph snowflakes are essentially the same as used today, and whilst the quality of his photographs reflect the technical limitations of the equipment of the era, his photographs were the only ones for over a hundred years. The broadest collection of Bentley’s photographs is held by the Jericho Historical Society in his hometown of Jericho, Vermont.
Bentley donated his collection of original glass-plate photomicrographs of snow crystals to the Buffalo Museum of Science. A portion of this collection has been digitized and organized into a digital library.
Bentley was born on February 7, 1865, in Jericho, Vermont. He became interested in snowflakes when just a teenager on his family farm. He tried to draw what he saw through an old microscope given to him by his mother when he was fifteen. The snowflakes were too complex to record before they melted, so he attached a bellows camera to a compound microscope and, after much experimentation, photographed his first snowflake on January 15, 1885.
He would capture more than 5000 images of crystals in his lifetime. Each crystal was caught on a blackboard and transferred rapidly to a microscope slide. Even at subzero temperatures, snowflakes are ephemeral because they sublime.
Bentley poetically described snowflakes as tiny miracles of beauty and snow crystals as ice flowers. Despite these descriptions, Bentley brought a highly objective eye to his work, similar to the German photographer Karl Blossfeldt, who photographed seeds, seed pods, and foliage.
Bentley’s work gained attention in the last few years of the nineteenth century, after his word was first published in a magazine by Henry Crocker of Fairfax, Vermont; who consequently ended up with the largest private collection of Bentley’s words. Harvard Mineralogical Museum acquired some of his photomicrographs. In collaboration with George Henry Perkins, Professor of Natural History at the University of Vermont, Bentley published an article in which he argued that no two snowflakes are alike. This concept caught the public imagination and he published other articles in magazines, including National Geographic, nature, Popular Science, and Scientific American. His photographs have been requested by academic organizations worldwide.
In 1931, Bentley worked with William J. Humphreys of the U.S. Weather Bureau to publish Snow Crystals, a monograph illustrated with 2500 photographs. His other publications include the entry on snow in the fourteenth edition of the Encyclopedia Britannica.
Bentley also photographed all forms of ice and natural water formations including clouds and fog. He was the first American to record raindrop sizes and was one of the first cloud physicists.
He died of pneumonia at his farm on December 23, 1931, after walking home six miles in a blizzard. Bentley was memorialized in the naming of a science center in his memory at Johnson State College in Johnson, Vermont. Shortly before his death, his book Snow Crystals was published by McGraw-Hill and is still in print today.
A snowflake is either a single ice crystal or an aggregation of ice crystals which falls through the Earth’s atmosphere. They begin as snow crystals which develop when microscopic supercooled cloud droplets freeze. Snowflakes come in a variety of sizes and shapes. Complex shapes emerge as the flakes move through differing temperatures and humidity regions, such that individual snowflakes are almost unique in structure. Snow flakes encapsulated in rime form balls known as graupel. Snowflakes appear white in color despite being made of clear ice. This is due to diffuse reflection of the whole spectrum of light by the small crystal facets.
In warmer clouds, an aerosol particle, or ice nucleus must be present and in contact with the droplet to act as a nucleus. The particles that make the ice nuclei are very rare compared to nuclei upon which liquid cloud droplets form; however, it is not understood what makes them efficient. Clays, desert dust, and biological particles may be effective, although to what extent is unclear. Artificial nuclei include particles of silver iodide and dry ice, and these are used to stimulate precipitation in cloud seeding.
Once a droplet has frozen, it grows in the supersaturated environment, which is one where air is saturated with respect to ice when the temperature is below the freezing point. The droplet then grows by deposition of water molecules in the air, know as vapor, onto the ice crystal surface where they are collected. Because water droplets are so much more numerous than the ice crystals due to their sheer abundance, the crystals are able to grow to hundreds of micrometers or millimeters in size at the expense of the water droplets. This process is known as the Wegener-Bergeron-Findeision process. The corresponding depletion of water vapor causes the droplets to evaporate, meaning that the ice crystals grow at the droplet’s expense. These large crystals are an efficient source of precipitation, since they fall through the atmosphere due to their mass, and may collide and stick together in clusters or aggregates. These aggregates are usually the type of ice particles that falls to the ground. Guinness World Records lists the world’s largest aggregate snowflakes as those of January 1887 at Fort Keogh, Montana; allegedly one measured fifteen inches wide. Although this report by a farmer is doubtful, aggregates of three or four inches wide have been observed. Single crystals the size of a dime have been observed.
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