There was a rumbling and a jarring, as if the earth were convulsed under foot; volumes of dense black smoke shot upward, and in another instant these rolling, twisting volumes of black became lurid, and an explosion like that of a thousand great guns rent the air.

As fast as the eye could follow sheets of flame shot up out of the sea of smoke, climbing higher and higher, in lightning flashes, until the lurid tongues licked the air a quarter of a mile above the startled wilderness.

Explosion followed explosion, some of them coming in hollow, reverberating booms, others sounding as if in midair.

Unseen by the watchers, the heavens were filled with hurtling rocks; solid masses of granite ten feet square were thrown a hundred feet away; rocks weighing a ton were hurled still farther, as if they were no more than stones flung by the hands of a giant; chunks that would have crashed from the roof to the basement of a skyscraper dropped a third of a mile away.

For three minutes the frightful convulsions continued, and the tongues of flame leaped into the night.