Robert Mallet (1810–81), an Irish civil engineer who had been investigating the passage of artificial seismic waves, sought Royal Society support to test his theories in the field, after a devastating earthquake in Basilicata, a province in the Kingdom of Naples. The earthquake struck on 16 December 1857; in January 1858 Mallet began a month–long trek across this mountainous region, gathering a wealth of data and description. His report, illustrated by maps and diagrams, included several hundred monoscopic and stereoscopic photographs, a remarkably early scientific use of this technique. It was published in 1862 as Great Neapolitan earthquake of 1857: the first principles of observational seismology. The acknowledged value of Mallet's report led to its being reprinted in 1987 and, in 2004, its translation into Italian, with supporting materials. While the translation was in progress, a search for related correspondence in Italian and British archives yielded a vivid personal side of Mallet's expedition, absent from his own report.