that morning, when the party in the cavern had had their breakfast, with some hot tea made on a spiritlamp which mrs. cliff had brought, and had looked cautiously out at the sunlit landscape, and the sea beyond, without seeing any signs or hearing any sound of wicked men, there came a feeling of relief. there was, indeed, no great ground for such a feeling, but as the rackbirds had not come the day before nor during the night, perhaps they would not come at all. it might be they did not care whether the black man ran away or not. but captain horn did not relax his precautions. he would take no chances, and would keep up a watch day and night.
when, on the night before, the time had come for ralph's watch to end, his sister had awakened him, and when the captain, in his turn, was aroused, he had not known that it was not the boy who had kept watch during his sleep.
in the course of the morning mrs. cliff and edna, having been filled with an intense desire to see the wonderful subterranean lake, had been helped over the rocky barrier, and had stood at the edge of the water, looking over to where it was lighted by the great chasm in the side of the rocks, and endeavoring to peer into the solemn, cavernous distance into which it extended on the right. edna said nothing, but stood gazing at the wonderful scene—the dark, mysterious waters before her, the arched cavern above her, and the picture of the bright sky and the tops of the distant mountains, framed by the sides of the great opening which stretched itself upward like a cathedral window on the other side of the lake.
"it frightens me," said mrs. cliff. "to be sure, this water was our salvation, for we should have been dead by this time, pirates or no pirates, if we had not found it. but it is terrifying, for all that. we do not know how far it stretches out into the blackness, and we do not know how far down it goes. it may be thousands of feet deep, for all we know. don't go so near the edge, ralph. it makes me shudder."
when the little party had returned to the cavern, the captain and the two ladies had a long talk about the lake. they all agreed that the existence of this great reservoir of water was sufficient to account for the greenness and fertility of the little plateau outside. even if no considerable amount of water trickled through the cracks in the rocks, the moisture which arose from the surface of the water found its way out into the surrounding atmosphere, and had nourished the bushes and vines.
for some time they discussed their new-found water-supply, and they were all glad to have something to think about and talk about besides the great danger which overhung them.
"if it could only have been the lake without the rackbirds," said
mrs. cliff.
"let us consider that that is the state of the case," remarked edna. "we have the lake, and so far we have not had any rackbirds."
it was now nearly noon, and the captain looked around for ralph, but did not see him. he went to search for him, and finding that the boy had not passed maka, who was on watch, he concluded he must have gone to the lake. there was no reason why the restless youth should not seek to enliven his captivity by change of scene, but captain horn felt unwilling to have any one in his charge out of sight for any length of time, so he went to look for ralph.
he found no one on the rocky shelf. as there had been little reason to expect a water attack at this hour, mok had been relieved from guard for a meal and a nap. but as ralph was not here, where could he be? a second glance, however, showed the captain the boy's clothes lying close by, against the upright side of the rock, and at that moment he heard a cry. his eyes flashed out toward the sound. there on the other side of the water, sitting on a bit of projecting rock not far from the great opening in the cave, he saw ralph. at first the captain stood dumb with amazement, and he was just about to call out, when ralph shouted again.
"i swam over," he said, "but i can't get back. i've got the cramps. can't you make some sort of a raft, and come over to me! the water's awfully cold."
raft, indeed! there was no material or time for anything of the kind. if the boy dropped off that bit of rock, he would be drowned, and the captain did not hesitate a moment. throwing aside his jacket and slipping off his shoes, he let himself down into the water and struck out in ralph's direction. the water was, indeed, very cold, but the captain was a strong swimmer, and it would not take him very long to cross the lake at this point, where its width was not much more than a hundred feet. as he neared the other side he did not make immediately for ralph. he thought it would be wise to rest a little before attempting to take the boy back, and so he made for another point of rock, a little nearer the opening, urging the boy, as he neared him, to sit firmly and keep up a good heart.
"all right," said ralph. "i see what you are after. that is a better place than this, and if you land there i think i can scramble over to you."
"don't move," said the captain. "sit where you are until i tell you what to do."
the captain had not made more than two or three strokes after speaking when his right hand struck against something hard, just below the surface of the water. he involuntarily grasped it. it was immovable, and it felt like a tree, a few inches in diameter, standing perpendicularly in the lake. wondering what this could be, he took hold of it with his other hand, and finding that it supported him, he let his feet drop, when, to his surprise, he found that they rested on something with a rounded surface, and the idea instantly came into his mind that it was a submerged tree, the trunk lying horizontally, from which this upright branch projected. this might be as good a resting-place as the rock to which he had been going, and standing on it, with his head well out of the water, he turned to speak to ralph. at that moment his feet slipped from the slimy object on which he stood, and he fell backward into the water, still grasping, however, his upright support. but this did not remain upright more than an instant, but yielded to his weight, and the end of it which he held went down with him. as he sank, the captain, in his first bewilderment, did not loosen his grasp upon what had been his support, and which still prevented him from sinking rapidly. but in a moment his senses came to him, he let go, and a few downward strokes brought him to the surface of the water. then he struck out for the point of rock for which he had been aiming, and he was soon mounted upon it.
"hi!" shouted ralph, who had been so frightened by the captain's sudden sinking that he nearly fell off his narrow seat, "i thought something had pulled you down."
the captain did not explain. he was spluttering a little after his involuntary dive, and he wanted to get back as soon as possible, and so wasted no breath in words. in a few minutes he felt himself ready for the return trip, and getting into the water, he swam to ralph. following the directions given him, the boy let himself down into the water behind the captain, and placed his hands upon the latter's hips, firmly grasping the waistband of his trousers. then urging the boy not to change his position, nor attempt to take hold of him in any other way, the captain struck out across the lake, ralph easily floating behind him.
when they stood upon the shelf on the other side, and ralph, having rubbed himself down with the captain's jacket, put on his clothes, captain horn rather sternly inquired of him how he came to do such a foolish and wicked thing as to run the risk of drowning himself in the lake at a time when his sister and his friends had already trouble enough on their minds.
ralph was sorry, of course, that the captain had to come after him, and get himself wet, but he explained that he wanted to do something for the good of the party, and it had struck him that it would be a very sensible thing to investigate the opening on the other side of the lake. if he could get out of that great gap, he might find some way of climbing out over the top of the rocks and get to the place where his flag was, and then, if he saw mr. rynders coming, he could wave it. it would be a great thing if the people in the vessel which they all expected should see that flag the moment they came in sight of the coast. they might get to shore an hour or two sooner than if they had not seen it.
"if the cramp in this leg had kept off five minutes longer," he said, "i would have reached that big hole, and then, if i could have climbed over the top of the rocks, i could have come down on the other side to the front door, and asked maka to get me my clothes, so i would not have had to swim back at all."
"that will do," said the captain. "and now that you are dressed, you can go inside and get me that woollen shirt and trousers that i use for a pillow, for i must take off these wet things."
when the boy came back with the clothes, the captain told him that he need not say anything to his sister or mrs. cliff about the great danger he had been in, but before he had finished his injunction ralph interrupted him.
"oh, i have told them that already," said he. "they wanted to know where i had been, and it did not take a minute to tell them what a splendid swimmer you are, and how you came over after me without taking as much as two seconds to think about it. and i let them know, too, that it was a mighty dangerous thing for you to do. if i had been one of those fellows who were not used to the water, and who would grab hold of any one who came to save them, we might both have gone to the bottom together."
the captain smiled grimly. "it is hard to get ahead of a boy," he said to himself.
it was late that afternoon when captain horn, with ralph and the two ladies, were standing on the rocks in the inner apartment, trying to persuade themselves that they were having a cosey cup of tea together, when suddenly a scrambling sound of footsteps was heard, and maka dashed through the two adjoining apartments and appeared before them. instantly the captain was on his feet, his gun, which had been lying beside him, in his hand. up sprang the others, mute, with surprise and fear on their faces. maka, who was in a state of great excitement, and seemed unable to speak, gasped out the one word, "gone!"
"what do you mean?" cried the captain.
maka ran back toward the passage, and pointed inward. instantly the captain conjectured what he meant. mok, the second african, had been stationed to watch the lake approach, and he had deserted! now the hot thought flashed upon the captain that the rascal had been a spy. the rackbirds had known that there were shipwrecked people in these caves. how could they help knowing it, if they had killed davis and the others? but, cowardly hounds as they were, they had been afraid to attack the place until they knew how many people were in it, what arms they had, and in what way the place could best be assailed. this mok had found out everything. if the boy could swim across the lake, that black man could do it, and he had gone out through the cleft, and was probably now making his report to the gang.
all this flashed through the captain's brain in a few seconds. he set his teeth together. he was ashamed that he had allowed himself to be so tricked. that african, probably one of the gang, and able to speak english, should have been kept a prisoner. what a fool he had been to treat the black-hearted and black-bodied wretch as one of themselves, and actually to put him on guard!
of course, it was of no use to go to look for him, and the captain had put down his gun, and was just about to turn to speak to the others, when maka seized him by the coat. the negro seemed wildly excited and still unable to speak. but it was plain that he wanted the captain to follow him along the passage. there was no use in asking questions, and the captain followed, and behind him came ralph, edna, and mrs. cliff.
maka was about to climb over the rocky partition which divided the passage, but the captain stopped him. "stay here," said he, "and watch the passage. i will see what is the matter over there." and then he and ralph jumped over and hurried to the lake. as they came out on the little platform of rock, on which the evening light, coming through the great; cleft, still rendered objects visible, they saw mok crouching on his heels, his eyes wide open as usual.
the captain was stupefied. that african not gone! if it were not he, who had gone?
then the captain felt a tight clutch upon his arm, and ralph pulled him around. casting eyes outward, the captain saw that it was the lake that had gone!
as he and ralph stood there, stupefied and staring, they saw, by the dim light which came through the opening on the other side of the cavern, a great empty rocky basin. the bottom of this, some fifteen or twenty feet below them, wet and shining, with pools of water here and there, was plainly visible in the space between them and the open cleft, but farther on all was dark. there was every reason to suppose, however, that all the water had gone from the lake. why or how this had happened, they did not even ask themselves. they simply stood and stared.
in a few minutes they were joined by edna, who had become so anxious at their absence and silence that she had clambered over the wall, and came running to them. by the time she reached them it was much darker than when they had arrived, but she could see that the lake had gone. that was enough.
"what do you suppose it means?" she said presently. "are we over some awful subterranean cavern in which things sink out of sight in an instant?"
"it is absolutely unaccountable," said the captain. "but we must go back to mrs. cliff. i hear her calling. and if maka has come to his senses, perhaps he can tell us something."
but maka had very little to tell. to the captain's questions he could only say that a little while before, mok had come running to him, and told him that, being thirsty, he had gone down to the edge of the lake to get a drink, and found that there was no water, only a great hole, and then he had run to tell maka, and when maka had gone back with him, so greatly surprised that he had deserted his post without thinking about it, he found that what mok had said was true, and that there was nothing there but a great black hole. mok must have been asleep when the water went away, but it was gone, and that was all he knew about it.
there was something so weird and mysterious about this absolute and sudden disappearance of this great body of water that mrs. cliff became very nervous and frightened.
"this is a temple of the devil," she said, "and that is his face outside. you do not know what may happen next. this rocky floor on which we stand may give way, and we may all go down into unknown depths. i can't think of staying here another minute. it is dark now. let us slip away down to the beach, and take the boat, and row away from this horrible region where human devils and every other kind seem to own the country."
"oh, no," said the captain, "we can't consider such wild schemes as that. i have been thinking that perhaps there may be some sort of a tide in this lake, and in the morning we may find the water just as it was. and, at any rate, it has not entirely deserted us, for in these pools at the bottom we can find water enough for us to drink."
"i suppose i would not mind such things so much," said mrs. cliff, "if they happened out of doors. but being shut up in this cave with magical lakes, and expecting every minute to see a lot of bloodthirsty pirates bursting in upon us, is enough to shake the nerves of anybody."
"captain," said ralph, "i suppose you will not now object to letting me go in the morning to explore that opening. i can walk across the bottom of the lake without any danger, you know."
"don't you try to do anything of the kind," said the captain, "without my permission."
"no, indeed!" exclaimed mrs. cliff. "supposing the water were to suddenly rise just as you were half-way across. now that i think of it, there are springs and bodies of water which rise and fall this way, some of them in our own western country, but none of them are as large as this. what if it should rise in the night and flood the cave while we are asleep?"
"why, dear mrs. cliff," said edna, "i am not afraid of the water's rising or of the earth's sinking. don't let us frighten ourselves with imaginations like that. perhaps there may not even be any real thing to be afraid of, but if there should be, let us keep courage for that."
the disappearance of the lake gave the captain an uneasiness of which the others had not thought. he saw it would be comparatively easy for the rackbirds to gain access to the place through the cleft in the eastern wall of the lake cavern. if they should discover that aperture, the cavern might be attacked from the rear and the front at the same time, and then the captain feared his guns would not much avail.
of course, during the darkness which would soon prevail there was no reason to expect a rear attack, and the captain satisfied himself with leaving mok at his former post, with instructions to give the alarm if he heard the slightest sound, and put maka, as before, in the outer passage. as for himself, he took an early nap in the evening, because at the very first break of dawn it would be necessary for him to be on the alert.
he did not know how much he had depended upon the lake as a barrier of defence, but now that it had gone, he felt that the dangers which threatened them from the rackbirds were doubled.
