As communication between various parts of the world became more common, earthquake observations from throughout the world could be combined. Following an earthquake in Chile in 1822, the author Maria Graham reported systematic changes in the elevation of the Chilean coastline. Observations of coastline changes were confirmed following the 1835 Chilean earthquake by Robert FitzRoy, captain of the H.M.S. Beagle, while Charles Darwin was onshore examining the geology of the Andes.
In the 1850s, 60s, and 70s, three European contemporaries made cornerstone efforts in seismology. Robert Mallet, an engineer born in Dublin who designed many of London's bridges, measured the velocity of seismic waves in the earth using explosions of gunpowder. His idea was to look for variations in seismic velocity that would indicate variations in the properties of the earth. This same method is still used today, for example in oil field exploration. Robert Mallet was also one of the first to estimate the depth of an earthquake underground.
At the same time as Mallet was setting off explosions of gunpowder in England, Alexis Perrey, in France, was making quantitative analyses of catalogs of earthquakes. He was looking for periodic variations of earthquakes with the seasons and with lunar phases. And in Italy, Luigi Palmieri invented an electromagnetic seismograph, one of which was installed near Mount Vesuvius and another at the University of Naples. These seismographs were the first seismic instruments capable of routinely detecting earthquakes imperceptible to human beings.
The foregoing work set the stage for the late 1800s and early 1900s, when many fundamental advances in seismology would be made. In Japan, three English professors, John Milne, James Ewing, and Thomas Gray, working at the Imperial College of Tokyo, invented the first seismic instruments sensitive enough to be used in the scientific study of earthquakes.