In 1885, after attaching a bellows camera to a compound microscope, Bentley became the first known snowflake photographer. He went on to develop a highly successful method of photographing the ephemeral snow crystals on a black velvet backing before they melted. Bentley also collaborated on the article that proposed the idea that no two snowflakes are alike. In 1931, some 2,000 of Bentley’s 5,000 snowflake photographs were published in a book titled what? Discuss