ten o’clock
It was impossible for Cyrus Harding and Ayrton , with these impediments , to make rapid progress . Moreover , the atmosphere was close , as if the oxygen had been partly burned up , and had become unfit for respiration . At every hundred paces they were obliged to stop to take breath . It was therefore past ten o'clock when the engineer and his companion reached the crest of the enormous mass of rocks of basalt and porphyry which composed the northwest coast of the island . Ayrton and Cyrus Harding commenced the descent of this abrupt declivity , following almost step for step the difficult path which , during that stormy night , had led them to Dakkar Grotto . In open day the descent was less perilous , and , besides , the bed of ashes which covered the polished surface of the rock enabled them to make their footing more secure . The ridge at the end of the shore , about forty feet in height , was soon reached .