Leiden University at the university. The learning and reputation of Jacobus Gronovius, Herman Boerhaave, Tiberius Hemsterhuis and David Ruhnken, among others, enabled Leiden to maintain its reputation for excellence down to the end of the 18th century. At the end of the nineteenth century, Leiden University again became one of Europe's leading universities. At the world’s first university low-temperature laboratory, professor Heike Kamerlingh Onnes achieved temperatures of only one degree above absolute zero of −273 degrees Celsius. In 1908 he was also the first to succeed in liquifying helium and can be credited with the discovery of the superconductivity in metals. The
What Katy Did School (set in Hanover, New Hampshire); "What Katy Did Next", in which a new friend of Katy's takes her on a once-in-a-lifetime trip to Europe; "Clover", in which Katy is married and Clover accompanies her brother Phil to Colorado after he falls ill; and "In the High Valley", which shows the lives of a handful of young people living in the High Valley in Colorado, including Clover, Elsie and their husbands. What Katy Did What Katy Did is an 1872 children's book written by Sarah Chauncey Woolsey under her pen name Susan Coolidge. It follows the adventures of a twelve-year-old