context: Tesla invented a steam-powered mechanical oscillator—Tesla's oscillator. While experimenting with mechanical oscillators at his Houston Street lab, Tesla allegedly generated a resonance of several buildings. As the speed grew, it is said that the machine oscillated at the resonance frequency of his own building and, belatedly realizing the danger, he was forced to use a sledge hammer to terminate the experiment, just as the police arrived.:162–164 In February 1912, an article—"Nikola Tesla, Dreamer" by Allan L. Benson—was published in World Today, in which an artist's illustration appears showing the entire earth cracking in half with the caption, "Tesla claims that in a few weeks he could set the earth's crust into such a state of vibration that it would rise and fall hundreds of feet and practically destroy civilization. A continuation of this process would, he says, eventually split the earth in two."
question: What caused Tesla to sledge hammer his oscillator?