The greatest danger to which we had yet been exposed was now over, but there remained much anxiety in my mind lest another serpent might, unseen by us, have entered the swamp, or might appear, as this had done, from the country beyond Falconhurst. I projected then two excursions, the first to make a thorough examination of the thicket and morass; the next right away to the Gap, through which alone the archenemy could have entered our territory. On summoning my sons to accompany me to the marsh, I found neither Ernest nor Jack very eager to do so, the latter vowing he had the cold shivers each time he thought how his ribs might have been smashed by the last flap of the snake's tail; but I did not yield to their reluctance, and we finally set about crossing the marsh by placing planks and wicker hurdles on the ground, and changing their places as we advanced. Nothing was discovered beyond tracks in the reeds and the creature's lair; where the rushes, grass, and bog-plants were beaten down. Emerging beyond the thicket we found ourselves on firm ground, near the precipitous wall of rock, and perceived a clear sparkling brook flowing from an opening, which proved to be a cave or grotto of considerable size. The vaulted roof was covered with stalactites, while many formed stately pillars, which seemed as though supporting the roof. The floor was strewn with fine snow-white earth, with a smooth soapy feeling, which I felt convinced was fuller's earth. "Well, this is a pleasant discovery!" said I. "This is as good as soap for washing, and will save me the trouble of turning soap-boiler." Perceiving that the streamlet flowed from an opening of some width in the inner rock, Fritz passed through, in order to trace it to its source, presently shouting to me that the opening widened very much, and begging me to follow him. I did so, leaving the other boys in the outer cave, and fired a pistol-shot--the reverberating echoes of which testified to the great extent of the place; and lighting the bit of candle I always carried with me, we advanced, the light burning clear and steadily, though shedding a very feeble light in so vast a space. Suddenly Fritz exclaimed: "I verily believe this is a second cave of salt! See how the walls glance! and how the light is reflected from the roof!" "These cannot be salt crystals," said I; "the water which flows over them leaves no track, and tastes quite sweet. I am rather inclined to believe that we have penetrated into a cave of rock crystal!" "Oh, how splendid! Then we have discovered a great treasure!" "Certainly, if we could make any use of it; otherwise, in our situation, it is about as valuable as the lump of gold found by good old Robinson Crusoe." "Anyhow, I will break off a piece for a specimen. See, here is a fine bit, only rather dull, and not transparent; what a pity! I must knock off another."