It has been discovered by extensive observations, that this agency does not exert itself in individual spots, so as to produce here a Volcano and there an Earthquake; but its operations take place over long tracts of country in which the Volcanoes are placed, and, in the spaces between them, Earthquakes are more or less frequent. These tracts are called Volcanic bands; one of them extends nearly parallel with the West Coast of South America, along the chain of mountains called the Andes, which you will see marked on the map; and another much smaller extends from Mount Vesuvius to Mount Etna, with the Volcanic Island Stromboli, and several extinct Volcanoes lying between them, and then turns to the East, through several of the Greek Islands, and passes on to Syria, where Earthquakes are frequent. Earthquakes in their simplest form are nothing more than violent shakings of the ground; but sometimes the earth is split open; sometimes it is raised; and sometimes it is depressed. I shall tell you of some of the changes which took place in the great Earthquake of Calabria, which lies in the smaller volcanic band I mentioned to you between Vesuvius and Etna. EARTHQUAKE OF CALABRIA. The shocks began in 1783, and lasted for nearly four years, till the end of 1786. During this time the King of Naples sent persons to take correct notes and representations of all that was going on, and we have therefore got a better account of it than we have of any other Earthquake that ever occurred. The convulsion of the earth, sea, and air, extended as far as Naples, and over the whole of Sicily; but the district over which it was so violent as to excite intense alarm, was about five hundred miles in circumference.