Together with his colleagues Thomas Gray and James Ewing, he began a course of research and instrumental development lasting sixteen years and culminating in the successful construction in 1896 of the first seismograph, capable of recording major earthquakes occurring in any part of the world. Waves from a distant earthquake were detected by a horizontal pendulum which recorded on photographic paper rotated by a drum. This instrument was soon manufactured by the firm of R. W. Munro.