About eight o'clock in the evening
I had every reason to believe from this that our descent was far more horizontal than vertical . As for discovering the exact depth to which we had attained , nothing could be easier . The Professor as he advanced measured the angles of deviation and inclination ; but he kept the result of his observations to himself . About eight o'clock in the evening , my uncle gave the signal for halting . Hans seated himself on the ground . The lamps were hung to fissures in the lava rock . We were now in a large cavern where air was not wanting .