Abbe required that the weather service stay at the forefront of technology. Over time, the instrument division at the headquarters tested and calibrated thousands of devices and even began to design and build their own instruments. By the end of the century, self-registering equipment came into use, and the United States led the meteorological world with 114 Class I (automatic recording) observation stations. Anticipating an increase in international cooperation, Abbe began to seek quality instruments calibrated to international standards. He enlisted Oliver Wolcott Gibbs of Harvard and Arthur Wright of Yale to design improved equipment. For comparison purposes, Abbe ordered a barometer from Heinrich Wild (director of the Nicholas Central Observatory in Russia), as well as an anemometer and several types of hygrometers from Germany. Abbe then invented an anemobarometer to test the effect of chimney and window drafts on barometers in enclosed spaces.