"Come away, children," cried I, in terror; "the air you would breathe there is certain death." I explained to them that, under certain circumstances, carbonic acid gas was frequently accumulated in caves or grottoes, rendering the air unfit for respiration; producing giddiness of the head, fainting, and eventually death.

I sent them to collect some hay, which I lighted and threw into the cave; this was immediately extinguished; we repeated the experiment several times with the same result.

I now saw that more active means must be resorted to.
We had brought from the vessel a box of fireworks, intended for signals; I threw into the cave, by a cord, a quantity of rockets, grenades, &c., and scattered a train of gunpowder from them; to this I applied a long match, and we retired to a little distance.

This succeeded well; a great explosion agitated the air, a torrent of the carbonic acid gas rushed through the opening, and was replaced by the pure air; we sent in a few more rockets, which flew round like fiery dragons, disclosing to us the vast extent of the cave.

A shower of stars, which concluded our experiment, made us wish the duration had been longer.