Page:Popular Science Monthly Volume 77.djvu/616

610 general trend of the less broken lava streams, we gradually worked upward and inward toward the main axis of the whole lava mass, indicated by vents which gave egress to steam and gases discharged by fluid lava running through tunnels beneath the surface.

The great crater (Fig. 3) is a perfectly typical cone of cinders and lava, with a height from base to summit of four hundred feet as measured by the aneroid barometer. On three sides it is composed mainly of ashes and pumice, but toward the sea its surface displays smoother areas of rock where the lava formerly welled over the edge before the tunnels were formed by which the discharge now takes place. Large bombs, rounded masses of rock hurled from the crater during some explosive eruption, occur on the slopes, sometimes covered as by a sheet of tar with a later-extruded layer of lava (Fig. 6).

When we stood upon the extreme edge of the jagged margin and looked down upon the immense lake of fiery lava, four hundred feet below, it was hard to realize that the scene was actual and not an imaginary panorama of Dantesque infernal regions. The yawning cavity of the crater extended a full half mile in length, and its width was more than four hundred yards. Almost perpendicular and sometimes undercut, the crater walls dropped hundreds of feet to the lake of molten lava, which was in such violent commotion that it seemed to be liquid flame rather than a mass of fused and fiery rock. At certain places it boiled with greater activity, sending huge jets and fountains high into the air. Its waves moved variously at different times, but ever and again they would surge heavily to dash against the wall where the tunnels opened to give exit for the flow to the ocean. And always from this surface, thin steam-like vapor charged with acid gases swirled upward in the draught caused by the strongly-blowing trade winds, making it excessively unpleasant to look over the edge even from the windward side.

Magnificent though it was by day, the scene at night was far beyond human powers of description. With the darkness, the lake glowed almost as a continuous incandescent mass. Its light was reflected upon the clouds above, making a beacon that we had often seen from a distance of forty miles and which was said to have been visible at a distance of seventy miles during the period of the volcano's greatest activity about two years earlier. Looking seaward, the rosy vapors above the tunnel vents outlined the course of the lava down to the shore of the island where the fire of the final lava cascades gave color to two huge clouds of steam. Again and again through the night we climbed from our camp at the base of the cone to look down upon the fascinating but awful marvel, whose fires illuminated the scene so as to give ample light to guide a way over the broken lava.

Leaving now the volcano of Savaii, which is a veritable classic in its regularity of structure and mode of origin, we pass to the Hawaiian