“ Devoting much attention to pure science, he became especially distinguished for his researches on earthquakes, and from 1852–1858 he was engaged (with his son John William Mallet) in the preparation of his great work, The Earthquake Catalogue of the British Association (1858) . In 1862 he published two volumes, dealing with the Great Neapolitan Earthquake of 1857 and The First Principles of Observational Seismology. He then brought forward evidence to show that the depth below the earth’s surface, whence came the impulse of the Neapolitan earthquake, was about 8 or 9 geographical miles. ”