There were three more eruptions in the seventeenth century, and from that date there set in a period of far more frequent outbursts, which have continued to our own times. In the eighteenth century there were twenty-three distinct eruptions, lasting each from a few hours to two or three days, and of varying degrees of violence–a vast steam-jet forcing up cinders and stones from the crater into the air, usually accompanied by the outflow of lava, from cracks in sides of the crater, in greater or less quantity. In the nineteenth century there were twenty-five distinct eruptions, the most formidable of which were those of 1822, 1834, and 1872. All of the eruptions of Vesuvius in the last 280 years have been carefully described, and most of them recorded in coloured pictures (a favourite industry of the Neapolitans), showing the appearance of the active volcano both by day and night and its change of shape in successive years. Sir William Hamilton, the British Ambassador at the Court of Naples at the end of the eighteenth century (of whose great folio volumes I am the fortunate possessor), largely occupied himself in the study and description of Vesuvius, and published illustrations of the kind mentioned above, showing the appearance of the mountain at various epochs. Since his day there has been no lack of descriptions of every succeeding eruption, and now we have the records of photography. The crater or basin formed by a volcano starts with the opening of a fissure in the earth's surface communicating by a pipe-like passage with very deeply-seated molten matter and steam. Whether the molten matter thus naturally "tapped" is only a local, though vast, accumulation, or is universally distributed at a given depth below the earth's crust, and at how many miles from the surface, is not known. It seems to be certain that the great pressure of the crust of the earth (from five to twenty-five miles thick) must prevent the heated matter below it from becoming either liquid or gaseous, whether the heat of that mass be due to the cracking of the earth's crust and the friction of the moving surfaces as the crust cools and shrinks, or is to be accounted for by the original high temperature of the entire mass of the terrestrial globe. It is only when the gigantic pressure is relieved by the cracking or fissuring of the closed case called "the crust of the earth" that the enclosed deep-lying matter of immensely high temperature liquefies, or even vaporizes, and rushes into the up-leading fissure. Steam and gas thus "set free" drive everything before them, carrying solid masses along with them, tearing, rending, shaking "the foundations of the hills," and issuing in terrific jets from the earth's surface, as through a safety valve, into the astonished world above. Often in a few hours they choke their own path by the destruction they produce and the falling in of the walls of their briefly-opened channels. Then there is a lull of hours, days,