Otto van Guericke builds the first electric machine. It was made of a large sulfur ball cast inside a glass globe, mounted on a shaft. The ball was rotated by means of a crank and a static electric spark was produced when a pad was rubbed against the ball as it rotated. Later editions increased the speed of the rotation with a belt and and rotating wheel. Electrical demonstrations became a favorite parlor trick for guests, but the electric machine also allowed serious scientists to perform experiments that could not be performed earlier. It was Guericke who noted that like charges repelled each other.