resolves itself into a volcanic crater with an inner cone, as every active volcano has. It is rather ludicrous to suppose that polyps, among the lowest of created beings, leading an ephemeral existence, should yet have such unanimity of purpose, such perfect mutual understanding, as to undertake to build their reefs in a more or less circular form; it is preposterous to suppose the unvarying form of the structure is the result of mere chance. Clearly we must find some other influences; and the most reasonable is to suppose the foundations of these islands were laid by the same agency that raised all other Oceanic islands from the bed of the sea. The volcano thus plays an important part in the earth’s economy. Not only does it add to land areas by upheaval from the deep. The amount of material thrown out by the Javanese volcanoes alone during the past hundred years is greater far than all the silt borne to the sea by American rivers during the same period. Krakatoa, in its recent eruption, threw out more than the Mississippi bears to the sea in sixty years. There is some doubt as to how much volcanoes effect by direct upheaval. The formation of many observed cones shows that the majority are mainly built up by the materials thrown out, and not by any great elevation of the adjacent surface. In the case of a volcano already existing, it is of course not easy to know what proportion of its mass is merely accumulation of lava, cinders, or tufa. As to the form of volcanic cones, those of ashes, cinders, and scoria are of course steepest; those of lava thrown out when liquid having a very gradual slope. The difference may be readily illustrated by comparing a heap of sand and pebbles with a heap of stiffening molasses candy. One is steeply conical; the other, rounded or dome-like. But either form of volcano may abound in crevices and apertures from which issue sulphurous vapors and gases. These fumaroles, as they are called, are usually surrounded with mineral deposits, often resembling the most delicate filigree work. Having considered the general phases and principles of volcanic action, we may now notice some of the more famous eruptions of the past. CHAPTER XXI. GREAT ERUPTIONS OF VESUVIUS. “E’en while they cheered the gladiator’s thrust, And shouted as the lion crunched his bones, Up sprang the Fire King from his ages’ sleep Shook wide his robe of ever-deepening night, And flung his fiery banner on the wind. The groaning earth then trembled at his tread, And thousand thunders rent the raging mount, While prince and pauper, ’mid the scorching gloom, Groped through the gaping streets; the ocean hissed, And palaces and marble temples reeled, And crushed or prisoned; still the ashes fell, Till mansions, statues, homes and colonnades, And Strength, and Beauty, Love, and Life, and Death, Lay heaps on heaps, in one black ruin blent.”