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." "You must go more carefully to work, or it will look as dull as the first. You destroyed its true form, which is that of a pyramid, with six sides or faces." We remained some time in this interesting grotto, but our light burnt low after we had examined it in different directions; and Fritz having secured a large lump, which exhibited several crystals in perfection, we quitted the place, Fritz discharging a farewell shot for the sake of hearing the grand echoes. On reaching the open air we saw poor Jack sobbing bitterly, but as soon as we appeared he ran joyfully toward us, and threw himself into my arms. "My child, what is the matter?" I cried anxiously. "Oh, I thought you were lost! I heard a noise twice, as if the rocks had shattered down; and I thought you and Fritz were crushed in the ruins! It was horrible! How glad I am to see you!" I comforted the child, and explained the noises he had heard, inquiring why he was alone. "Ernest is over there among the reeds; I daresay he did not hear the shots." I found Ernest busily engaged in weaving a basket in which to catch fish; he had devised it ingeniously, with a funnel-shaped entrance; through which the fish passing would not easily find their way out, but would remain swimming about in the wide part of the apparatus. "I shot a young serpent while you were away, father," said he. "It lies there covered with rushes; it is nearly four feet long, and as thick as my arm." "A serpent!" cried I, hurrying toward it in alarm, and fearing there must be a brood of them in the swamp after all.