In the rents thus made the grinding ice flowed until it reached the internal furnace of the world, which generating gases and steam, explosions followed that tore wider the earth’s womb and made the region a fiery cave. Into the devious caverns thus formed water from underground rivers continues to flow, over subterranean fires that convert it into steam, and thus at the many vents we observe the ever active, though constantly waning, energies of the volcano. ------------------------------------------------------------------------ [Illustration: TOWER FALLS, IN THE GRAND CAÑON.—At this point the waters of Yellowstone River spring at one bound over a precipice 156 feet high, forming one of the most beautiful and picturesque falls to be found in any country. The castellated rocks surrounding the falls stand like grim sentinels guarding their beautiful treasure, and have been well and appropriately named, for their resemblance to ancient towers and battlements is so striking as to be recognized at a glance. This is one of the most attractive points along the entire length of Yellowstone Cañon. ] ------------------------------------------------------------------------ [Illustration: A PETRIFIED TREE IN THE BAD LANDS OF DAKOTA.—In many parts of the Northwest, particularly in the Bad Lands of Dakota and Yellowstone National Park, there are whole forests of petrified trees, partly standing or lying about in promiscuous profusion. A fine photograph of a portion of one of these trees is given on this page. According to the scientific theory, these forests were overwhelmed by the ice- flood many centuries ago, and each tree became, through chemical action, a thousand years or more thereafter, a gem-like pillar of the most exquisite beauty. Petrified remains of gigantic animals that roamed these ancient forests are found in abundance in the same regions. ] ------------------------------------------------------------------------ [Illustration: BISCUIT BASIN.—This is one of the most singular as well as beautiful formations in Yellowstone National Park. Terraced overflow basins like this are a most striking feature of the hot springs, and no description can do justice to their beauty, for neither the delicate fretwork of their walls, the frosted surface of the glistening deposit, nor the brilliant colors of the pools can be adequately described. The sides and bottom of the basin are formed of pure white travertine, while the varying depths cause the water to appear all shades between a peacock-blue and a light nile-green. Those who have seen Biscuit Basin will never lose the memory of the vision of beauty that it impresses upon the mind. ] ------------------------------------------------------------------------ [Illustration: CRATER OF OBLONG GEYSER.]