midnight
he said , `` see to what a region I have transported you . '' On gazing upwards , we saw stars innumerable glittering in the sky , so it seemed , but in vain we looked for those to which our eyes were accustomed , though it was difficult to persuade ourselves that they were not veritable stars . The guide , holding a stone in his hand , threw it upwards , when it struck the roof above our heads , and we found that the seeming stars were produced by pieces of mica imbedded in the roof on which the light from the lantern , being thrown in a peculiar way , was brightly reflected . Relighting our torches , we saw that the walls were of a yellow colour , while the ceiling appeared to be of a dark undefined blue , resembling the midnight sky . We visited several other caverns , some of which appeared to be of immense height , though the ceiling in most parts is not more than thirty feet from the ground . One cavern had , what looked like a mountain in that subterranean region , rising from the ground , with a stream running at its base . We crossed several rivers ; besides the `` Echo , '' one called the `` Styx , '' the other the `` Lethe . ''