On entering their defiles, therefore, they often hang offerings on the trees, or place them on the rocks, to propitiate the invisible "lords of the mountains," and procure good weather and successful hunting; and they attach unusual significance to the echoes which haunt the precipices.

This superstition may also have arisen, in part, from a natural phenomenon of a singular nature.

In the most calm and serene weather, and at all times of the day or night, successive reports are now and then heard among these mountains, resembling the discharge of several pieces of artillery.
Similar reports were heard by Messrs.

Lewis and Clarke in the Rocky Mountains, which they say were attributed by the Indians to the bursting of the rich mines of silver contained in the bosom of the mountains.
In fact, these singular explosions have received fanciful explanations from learned men, and have not been satisfactorily accounted for even by philosophers.

They are said to occur frequently in Brazil.