My uncle accompanied me in my next and several other visits to the upper valley, with the result that we obtained as many specimens of the beautiful orange birds as we required, and in addition several rare kinds of humming-birds; but strangely enough, anxious as I was that my uncle should see one of the pumas they were never encountered once.

The whole of the upper valley was very lovely, and the air, from its being so high up among the mountains, deliciously cool.

“It seems a pity,” my uncle said, “that nobody lives here.”  For as far as we could make out in our many journeys, human beings had never penetrated its solitudes.

“Yes,” I said, on one of these occasions, “it is a glorious place, uncle, and anyone might make it a lovely garden with hardly any trouble; but I shouldn’t like to live here after all.”

“Why?” he said.  “You seem very hard to please.”

“The place isn’t perfect, uncle,” I said.

“No place is, but I don’t see much to find fault with.  Oh, you mean that we can find no quetzals.”

“No, I did not,” I said.  “I meant we find too many rattlesnakes.”

“Ah, yes, they are a nuisance, Nat; but they always get out of our way if they can, and so long as they don’t bite us we need not complain.  Well, we have pretty well explored this valley, and it is time we tried another.  We must get farther to the south.”

“Why not strike off, then, from the top of the great cliff above the arch, and try and find where the stream dives down?”

“What!” he said; “you don’t think, then, that the stream rises entirely there?”

“No,” I said; “I fancy it dives underground when it reaches a mountain, and comes out where we saw.”

“Quite likely,” he said, jumping at the idea.  “We’ll try, for we have had some beautiful specimens from the woodlands on the banks of that stream.  Perhaps we may find my golden-green trogons up there after all, for I feel sure that there are some to be found up among the head-waters of the river.”

The next day preparations were made for our expedition, and as the country we were in seemed to be so completely uninhabited from its unsuitability for agricultural purposes, and the little attraction it had for hunters other than such as we, there was no occasion to mind leaving the boat.

The carpenter and Pete were in high glee at the news that they were to accompany us, and in the intervals of packing up, their delight was expressed by furtive punches and slaps delivered when one or the other was not looking.

“I am glad, Mr Nat,” Bill Cross said to me when we were alone for a few minutes overnight.  “I’m not grumbling, sir, and I like making cases and cooking and washing, but I do feel sometimes as if I’d give anything to be able to shoulder a gun and come along with you gents, shooting and hunting for curiosities.”

“Well, you’ll have a fine chance now, Bill,” I said.

“Yes, sir, and it’ll just be a treat; for I haven’t had much of the fun so far, have I?”

“Fun?” I said.

“Yes, sir; it’s fun to a chap like me who when he goes to sleep of a night it’s with the feeling that there’s a day’s work done.”

“So it is with all of us,” I said.  “I work very hard; so does my uncle.”

“Yes, sir; but don’t you see that what’s work to you as can go and do is seems like play to me as is obliged to stay in camp ­I mean with the boat.  But as I was going to say, after a night’s rest when one wakes up it’s always to begin another day’s work!  But there, don’t you think I’m grumbling, sir, because I arn’t; for I’ve never been so happy in my life before as since I’ve been out here with you and the doctor.  What time do we start to-morrow?”

“Breakfast before daylight, and start as soon as we can see,” I replied.

“Right, sir; I’ll be ready.”

There was so little novelty in a fresh trip to me then, that I dropped asleep as soon as I lay down in the tent under a big tree ashore, and it seemed like the next minute when the carpenter in his gruff voice called to us that breakfast was nigh ready.

I looked up, to see his face by the lanthorn he had brought alight, as he hung it from a hook on the tent-pole; and then after making sure that my uncle was awake, I hurried out into the darkness, where Pete was busy frizzling bacon over the glowing embers, ran down into the fresh, cool water for my bath, and came out with my blood seeming to dance through my veins.

Our breakfast was soon dispatched, and before the sun rose the tent had been fastened up, our guns and satchels shouldered and swung, and in addition Cross carried a coil of rope and the lanthorn, now out and freshly trimmed.

“Be useful,” he said, with a sage nod of the head.  “S’pose we shall be out all night.”

The next minute he and Pete shouldered the extra guns and the packs they were to carry in case our trip lasted over more than a couple of days; and we set off in single file steadily up the side of the stream between the walls of rock, and sometimes wading across it to find better ground.  Twice over we waded in the middle of the water, where it was sandy, and found it nowhere over our knees.

In due time we reached the spot where the walls of the gorge had drawn together and the end was closed by the perpendicular mountain at whose foot was the little natural arch out of which the water came gurgling swiftly.  Here my uncle stopped for the load-bearers to have a short rest before we began to climb upward to Puma Vale, as I had dubbed it.

Pete and Cross used their loads as seats, and the latter, who had not seen the place before, sat looking about attentively, while my uncle took out his little double-glass and examined the towering mountain for signs of birds upon the ledges or trees which clung to the sides.

The carpenter turned to me and nodded.

“Strange pretty place, Mr Nat,” he cried, “and it’s just like Pete said it was.  Going up yonder to try and find the river again farther on, aren’t we?”

“Yes, and I think we shall find it.”

“Wouldn’t it be better to keep on up it?  Should be sure of it then.”

“But don’t you see that we can go no farther?” I said wonderingly.

“No, sir, I don’t.  Water’s not above eighteen inches deep, and it’s nice sandy bottom.”

“But it nearly touches the top of the arch,” I said.

“Just there it do, sir, but that’s only the doorway; it may be ever so high inside.  P’raps I’m wrong, though.  You’ve tried it, then?”

“What, tried to get under that horrible dark arch?  Oh, no!”

“Why not?” said the man coolly.  “I don’t see nothing horrid.  Dessay it’ll be dark, but we’ve a lanthorn.”

“But we should have to wade, and in the darkness we might go down some horrible hole.”

Cross shook his head.

“Nay,” he said; “you might do that if the water was running the other way downward, but we should have to go up stream with the water coming to us.  We shouldn’t find any holes; what we should find more likely would be waterfalls, and have to climb up ’em.”

“What’s that?” cried my uncle, who had caught part of what was said, and he was told the rest.

“Let’s have a look, Nat,” he said, and slipping off our boots and stockings we waded on over the soft sand to where the water came rushing out through the arch, stooping down and peering in as we listened to the gurgling and whispering of the water.

“Shall we have the lanthorn, and I’ll stoop down and see if the roof gets higher farther in?” I said.

“Would you mind doing it?” said my uncle.

“I don’t think I should like it much,” I said; “but I’ll try.”

“Let me go, Master Nat, sir,” said Pete eagerly; “I won’t mind.”

“Sounds as if there’s plenty of room inside, sir,” said Cross, who had followed our example and waded in.

“Let’s see,” said my uncle, stooping down, after cocking his gun.  Then holding it as if it were a pistol, he reached in as far as he could and fired both barrels.

The reports sounded dull and smothered, and as we listened my uncle said: 

“It is only a narrow passage, I think.”

Then he was silent, for the reports were repeated ten times as loudly, and went on reverberating again and again, from farther and farther away, till they gradually grew indistinct and strange, for there was a strange dull roar growing louder and louder till the echoes were drowned, while the roar seemed to come on and on, till without hesitation on anyone’s part we turned and ran splashing out of the stream to the shore, to escape from a dark rushing cloud which came streaming out of the mouth of the cave with screams, hisses, and whisperings, out and away down the narrow ravine till it seemed to be filled with birds and bats, while a strange black-beetly odour assailed our nostrils.

“No doubt about there being plenty of room, lads,” said my uncle, as he laughed at our scared faces, for the sudden rush out was startling.

“Is them owls, sir?” said the carpenter, staring.

“No, no,” replied my uncle; “they are something of the goat-sucker tribe ­night-birds which build in caves; but a good half of what we see are bats.”

“Yes, I can see they’re bats, sir, and the biggest I ever did see.  Well, they won’t hurt us, sir?”

“No, but they’re terribly afraid we shall hurt them,” said my uncle.  “Well, Nat, what do you say?  Shall we explore the underground river?”

I felt as if I should like to say, “No, I would rather not,” but the pride within me made me take the other view of the matter.

“Yes,” I said, “of course,” and the sense of unwillingness was forgotten in the desire to laugh at the look of horror in Pete’s face as he stared appealingly from one to the other.

“You won’t mind, Cross?” said my uncle.

“No, sir; I should like it,” replied the man.

“Light the lanthorn.”

“Shall we take our loads with us, uncle?” I said.

“Certainly.  If the way through is short we shall want them at the other side.  If it is long we shall want some refreshments on the way.”

“But suppose ­” I began, and then I stopped.

“Suppose what?” said my uncle.

“Suppose the river does not pass through the mountain, but comes from deep down somewhere.”

“The more interesting the discovery of its hidden source, my lad.  But that is not likely.  Look at the rock.  What is it ­granite or gneiss?”

“No,” I said; “limestone.”

“Well, you ought to know how limestone ridges are honeycombed with water-formed caverns.  We have several examples at home.  If this subterranean river came bubbling up from somewhere in the interior and the rock were granite, I should expect it to be hot.”

“And it’s quite cold, sir,” said Cross.

“Oh, no, just pleasantly cool.  I don’t think there’s a doubt about its having its source higher up in the mountains; but whether it has dived down for a few hundred yards or a few miles we can only know by exploring.”

“Well, Cross,” I said to the carpenter, “will this be fun enough for you?”

“Splendid, sir,” said the man enthusiastically.  “I never had a treat like this.”

“Master Nat,” whispered Pete, “am I to come too?”

“Of course,” I said.  “Tuck up your trousers as high as you can.”

“But suppose we have to swim, sir?”

“Look here, Pete,” I said, “you don’t want to come.”

“No, sir.  Can’t help it, sir, but I never could a-bear the dark.”

“Then I’ll ask my uncle to let you stop behind.”

“What!” cried the poor fellow fiercely, “leave me behind, and you go?  That you just won’t, sir.  I’d go if it was twice as dark.”

I saw him set his teeth, and then, as my uncle gave the word, he climbed up to a verdant cleft with Cross to cut four stout bamboos about six feet long to act as walking-staves.

“We must always be ready to feel our way and try the depth,” said Uncle Dick; “and avoid any holes.  If it grows deeper as we go on and there is no bare rock at the sides, of course we must return.”

A few minutes later our guns were slung across our backs, the loads taken up, and, each armed with a staff, we made our start ­Cross, as he held the lanthorn, asking leave to lead the way.

“We shan’t be able to do it, Master Nat,” whispered Pete, as we followed in turn, Pete last, for it was very hard work, the barrels of our guns scraping again and again against the roof during the first twenty yards or so; but Pete had hardly uttered the above words before I saw Cross raise the lanthorn higher.  Then my uncle began to walk erect, and directly after I found on raising my staff that I could not touch the roof, while a sharp whistle uttered by our lanthorn-bearer was echoed from far on high.

“Plenty of room upwards, sir,” cried Cross.

“Yes,” said my uncle.

“Ugh! what a horrid place, Master Nat!” whispered Pete, who kept as close to me as he could.  “Do mind, sir.”

“Mind what?” I said.

“The holes.  If you step into one of them there’s no knowing how deep they are.  They must be just like wells.”

“How do you know?” I said gruffly; and he was silent, giving me time to look to right and left and forward, as far as the light of the lanthorn would allow.

There was not much to see ­only a faint halo of light, with reflections sometimes from dripping rocks; but it seemed that there was no shore to the river on either side such as would afford footing, while as far as I could make out the stream was about the same width as it was outside.

There was the dancing light on ahead, playing strangely on the surface of the gliding waters, and all around black darkness, while the vast cavern in which we were, seemed to be filled with strange sounds, splashings, ripplings, whisperings, and their echoes.

“Hear that, Master Nat?” said Pete, getting close beside me and grasping my arm.

“Of course I can,” I said pettishly, for it was bad enough to suffer from one’s own feelings, without being troubled at such a time by others.

“But ­oh, there it goes again,” he whispered.

“What goes again?” I said.

“That, sir.  I dunno what it is, but there seems to be lots of ’em.  Bill Cross stirs ’em up with the stick and the light, and they swims off both sides, and then you can hear ’em splashing with their tails as they come back again.”

“Nonsense!” I said.  “That’s all imagination.”

“Oh, no, it aren’t, sir,” he whispered.  “I say, what did you say was the name of them big snakes that lives part of their time in the water?”

“Anacondas.”

“That’s them, sir.  We’ve got all amongst ’em here, and they’ll be having one of us directly.”

“Pooh!  There’s nothing alive in this dark place,” I said scornfully.

“What!  Why, wasn’t it alive with birds and bats?”

“Oh, yes, but I don’t believe there’s a fish in these dark waters.”

“Fish!  Oh, I don’t mind fish, sir, as long as they aren’t sharks.  It’s them conders I can’t bear.  It wouldn’t so much matter if we were in the dark, but we’ve brought a light to show ’em where we are.”

“There are no snakes here,” I said angrily.

“It’s all very well for you to say so, Master Nat,” he replied; “but you just listen.  There!  Hear that?”

“Yes, the splash against the side of the wave we make in wading.”

Pete was about to say something more, but just then my uncle turned his head.

“Use your bamboo well, Nat,” he said, “in case of there being any cracks; but the bottom seems very level, and the depth keeps about the same.  Nice and cool here.  Keep close up.  What’s that, Cross?”

“Only a stone standing right up, sir; water washes round it.  It’s best to keep right in the middle, I think.”

“You must judge about that,” said my uncle.  “Go on.”

“How far do you think we’ve come, sir, now?”

“About a quarter of a mile, I should say.”

“That’s what I thought, sir,” said the carpenter, and he waded steadily on, with us following.

After a time it grew very monotonous, but we persevered, finding the underground river sometimes a little deeper, then shallower, so that the water rippled just above our ankles, while we knew at times that the cavern was wide and high, at others that it closed in on either side, and twice over the roof was so close that I could touch it with my stick.

The times when it opened out were plain enough, for our splashings or voices echoed and went whispering far away.  But otherwise the journey was very tame, and as the feeling of awe died away, the journey seemed uncommonly free from danger, for I felt it was absurd to imagine the waters to be peopled with strange creatures.

We had been wading on for quite a couple of hours, when the water began to grow more sluggish, and to flow very quietly, rising, too, higher and higher, till it was above our waists, and the light reflected from the surface showed that it was very smooth.

“Keep on, sir?” said Cross.

“Yes,” said my uncle.  “Keep on till it nearly touches your chin.  Then we’ll turn back.”

Pete uttered a low groan, but followed in a despairing way, while we went on for another quarter of an hour, with the water deeper and deeper, and at last, to our great delight, my uncle said: 

“There, the water is rippling up in my beard, so it is time to go back.”

“Hah!” ejaculated Pete, and then he groaned, for Cross said: 

“Not so deep now as it was ten minutes ago, sir.”

“Are you sure?”

“Yes, sir.  I know by my stick.  I keep my hand so that it touches the water, and I’ve had to move it twice in the last five minutes.  It’s not so deep now by three inches.”

“Go on, then,” said my uncle, and we followed, to find the water getting shallower rapidly now.  Ten minutes later it was below my waist, and in another ten minutes not above mid-thigh; but it had evidently widened out, for our voices seemed to go off far away into the distance, and my uncle suddenly said: 

“Why, Nat, the river must have widened out into a regular lake.  How shall we find the place where it narrows again?”

“Foller that there sound, sir, I think,” said Cross.

“What sound?” I said.

“That, sir; listen.  I can hear where it seems to be rushing in ever so far away.”

“Yes, I can hear it now,” I said.

“Forward, then,” said my uncle, and with the water once more but little above our knees we waded steadily on after the light which Cross bore breast-high.

“Cheer up, Pete,” I said; “we must be getting on now.  Why, if it came to the worst we could turn back.”

“Never find the way, sir,” he said bitterly, and then he uttered a yell, closely following upon a sharp ejaculation from the carpenter, who suddenly placed his foot in some cavity of the smooth floor, fell forward with an echoing splash, and the next moment the lanthorn disappeared beneath the gleaming surface, leaving us in utter darkness.

Wash, wash, ripple, ripple went the water, and the cries whispered away as fading echoes, and then Pete’s voice rose in a piteous wail.

“I knowed it, I knowed it,” he said.  “We shall never see the light again.  Oh, help, Master Nat, help!  Here’s one of them water-conders got me by the leg to pull me down.”

A cry that went to my heart and sent a shudder through every nerve, for the darkness seemed so thick that it might be felt.