Describes last letter to MH. [Letter continued 9 June in Naples:] Will write to J. H. Nelson. Problems with postal service in Naples. Met European nobility at dinner of British minister W. R. Hamilton. Ascent of Mount Vesuvius with Nicola Covelli. Barometer observations, chemical experiments, and camera lucida drawings. High society in Naples. Describes 'ridiculous' religious practices at church of Madonna dell'Arco and barbarian lower classes of Naples.