water had been concerned in the late eruption of Vesuvius; but during the whole of the preceding autumn, the fall of rain had been unusually great and continuous. There were frequent thunderstorms; and, on one occasion, the quantity of rain that fell was so great, as to cause a land-slip in Pizzifalcone, by which several houses were overwhelmed; and, on another occasion, the torrent of rain was so violent, that the Riviera di Chiaja was covered, to the depth of half a metre, with mud, and stones brought down by the water from the heights above. This enormous quantity of water pouring on the slopes of Vesuvius, and percolating through the crust of the earth into the fiery caverns, where volcanic forces are generated, being resolved into steam, and possibly aided by the expansion of volcanic gases, may have been a partial agent in propelling the formidable stream of lava which has caused such destruction. We observed, that when lava abounded, the projection of rocks and lapilli either ceased altogether, or became of small amount. The whole eruption ended in a shower of impalpable ashes, which hid the mountain for many days, and which were carried to a great distance by the wind. Sometimes the ashes were pure white, giving the mountain the appearance of being covered with snow. Vapour continued to rise from Vesuvius in beautiful silvery clouds, which ceased and left the edge of the crater white with sublimations. I owe to Vesuvius the great pleasure of making the acquaintance of Mr. Phillips, Professor of Geology in the University of Oxford; and, afterwards, that of Sir John Lubbock, and Professor Tyndall, who had come to Naples on purpose to see the eruption. Unfortunately, Sir John Lubbock and Professor Tyndall were so limited for time, that they could only spend one evening with us; but I enjoyed a delightful evening, and had much scientific conversation.