Christopher Hitchens in Vanity Fair:
We tend to love anecdotes about apples and eurekas because they make scientific genius seem more human and more random, but that other great Cambridge denizen Sir Leslie Stephen was closer to the mark when he claimed genius was “the capacity for taking trouble.” Isaac Newton was one of the great workaholics of all time, as well as one of the great insomniacs. His industry and application made Bertrand Russell look like a slacker (and, like Russell, he was morbidly afraid of fire among his papers and books—fire which did, in fact, more than once break out). When he decided that a reflecting telescope would be a better instrument than the conventional refracting model, he also decided to construct it himself. When asked where he had obtained the tools for this difficult task, he responded with a laugh that he had made the tools himself, as well. He fashioned a parabolic mirror out of an alloy of tin and copper that he had himself evolved, smoothed, and polished to a glass-like finish, and built a tube and mounting to house it. This six-inch telescope had the same effectiveness as a six-foot refracting version, because it removed the distortions of light that were caused by the use of lenses.
In contrast with this clarity and purity, however, Newton spent much of his time dwelling in a self-generated fog of superstition and crankery. He believed in the lost art of alchemy, whereby base metals can be transmuted into gold, and the surviving locks of his hair show heavy traces of lead and mercury in his system, suggesting that he experimented upon himself in this fashion, too. (That would also help explain the fires in his room, since alchemists had to keep a furnace going at all times for their mad schemes.) Not content with the narrow views of the philosopher’s stone and the elixir of life, he thought that there was a kind of universal semen in the cosmos, and that the glowing tails of the comets he tracked through the sky contained replenishing matter vital for life on Earth. He was a religious crackpot who, according to Ackroyd, considered Catholics to be “offspring of the Whore of Rome.”