geological wonder

The bottom now rose sensibly, and we soon arrived at long circuitous slopes, or inclined planes, which took us higher by degrees; but we were obliged to walk carefully among these conglomerates, bound by no cement, the feet slipping on the glassy crystal, fels...

Nevertheless, it appeared quite clear to me, that we were not in the principal chimney of the volcano, but in an accessory conduit, where we felt the counter shock of the great and principal tunnel filled by burning lava. It is impossible for me to say how man...