But Conseil’s dexterity and the Canadian’s strength surmounted all obstacles. At a height of about 31 feet the nature of the ground changed without becoming more practicable. To the conglomerate and trachyte succeeded black basalt, the first dispread in layers full of bubbles, the latter forming regular prisms, placed like a colonnade supporting the spring of the immense vault, an admirable specimen of natural architecture. Between the blocks of basalt wound long streams of lava, long since grown cold, encrusted with bituminous rays; and in some places there were spread large carpets of sulphur. A more powerful light shone through the upper crater, shedding a vague glimmer over these volcanic depressions for ever buried in the bosom of this extinguished mountain. But our upward march was soon stopped at a height of about two hundred and fifty feet by impassable obstacles. There was a complete vaulted arch overhanging us, and our ascent was changed to a circular walk. At the last change vegetable life began to struggle with the mineral. Some shrubs, and even some trees, grew from the fractures of the walls. I recognised some euphorbias, with the caustic sugar coming from them; heliotropes, quite incapable of justifying their name, sadly drooped their clusters of flowers, both their colour and perfume half gone. Here and there some chrysanthemums grew timidly at the foot of an aloe with long, sickly-looking leaves.