Others have endeavored to account for these discharges of "mountain artillery" on humbler principles; attributing them to the loud reports made by the disruption and fall of great masses of rock, reverberated and prolonged by the echoes; others, to the disengagement of hydrogen, produced by subterraneous beds of coal in a state of ignition.

In whatever way this singular phenomenon may be accounted for, the existence of it appears to be well established.

It remains one of the lingering mysteries of nature which throw something of a supernatural charm over her wild mountain solitudes; and we doubt whether the imaginative reader will not rather join with the poor Indian in attributing it to the thunderspirits, or the guardian genii of unseen treasures, than to any commonplace physical cause.
Whatever might be the supernatural influences among these mountains, the travellers found their physical difficulties hard to cope with.

They made repeated attempts to find a passage through or over the chain, but were as often turned back by impassable barriers.

Sometimes a defile seemed to open a practicable path, but it would terminate in some wild chaos of rocks and cliffs, which it was impossible to climb.