the crater, but during recent years the lava seldom, if ever, flows out over the crater rim. Instead, it breaks through the mountainsides at various altitudes, the great flow of 1919 having started at an altitude of about 8,000 feet. This stream of liquid rock, fully one-half of a mile wide, flowed for weeks down the mountainside and into the ocean, the waters of which, in contact with the highly heated lava, were thrown into terrific commotion. In 1885 a stream of lava several miles wide flowed forty-five miles. In one case, lava traveled the first fifteen miles in two hours, but this is an unusually great rate of speed. Lava streams in general seldom move faster than one or two miles per hour, and as the liquid rock gradually cools and becomes more and more viscous, the speed diminishes to zero. Almost incredible volumes of steam emanate from streams of molten lava. In 1840 an outflow of lava took place from the side of Kilauea Mountain and ran into the sea. Since that time the floor of the great crater pit (quoting Professor W. H. Hobbs) "has been essentially a movable platform of frozen lava of unknown and doubtless variable thickness which has risen and descended (hundreds of feet) like the floor of an elevator car between its guiding ways. The floor has, however, never been complete, for one or more open lakes are always to be seen, that of Halemaumau, located near the southwestern margin, having been much the most persistent. Within the open lakes the boiling lava is apparently white hot at a depth of but a few inches below the surface, and in the overturnings of the mass these hotter portions are brought to the surface and appear as white streaks marking the redder surface portions. From time to time the surface freezes over, the cracks open and erupt at favored points along the fissures, sending up jets and fountains of lava, the material of which falls in pasty fragments that build up driblet cones. Small fluid clots are shot out, carrying threadlike lines of lava glass behind them, the well-known 'Pelée's hair.' Sometimes the open lakes build up congealed walls, rising above the general level of the pit, and from their rim the lava spills over in cascades to spread out upon the frozen floor." In some regions, like the Columbian Plateau of the northwestern United States and the Deccan of India, each covering about 200,000 square miles, vast quantities of lava have been poured out layer upon layer to depths of even thousands of feet. Distinct volcanic cones or mountains in those regions are either absent or too scarce to look to as sources of so much lava. Such lava floods were probably mostly erupted from great fissures in the earth's crust, the fluidity to spread many miles.