“what’s that?” fairly yelled the professor.

“we am propelling ourselves in a contiguous direction an’ in close proximity to an elevated portion of th’ earth’s surface which rises in antiguous proximity t’ th’ forward part of our present means of locomotion!” said the colored man in a loud voice.

“which means there may be a collision,” the professor said, as he and the boys hurried toward the tower.

“jest what i said,” retorted washington. “what’ll i do?”

“send the ship a little higher,” answered mr. henderson. “we mustn’t hit any mountains.”

washington forced more gas into the holder, and speeded the negative gravity machine up some, so that the mermaid, which was flying rather low, ascended until it was in no danger of colliding with the peak which reared its lofty height just ahead of them.

as the ship sailed slowly over the mountain, mark gazed down and exclaimed:

“doesn’t that look like the ruins of some building?”

the professor took a pair of field glasses from a rack in the wall and took a long view.

“it must be the place,” he said in a low voice.

“what place?” asked jack.

“the temple of treasure,” was the answer. “hankos told me it was on top of the highest mountain in the land, and this must be it, for it is the loftiest place we have seen. but we must be careful, for there is danger down there.”

“what kind?” asked mark.

“the place was long ago deserted by the giants,” mr. henderson went on. “ages ago it was one of their storehouses for treasure, but there were wars among themselves, hankos said, and this part of the country was laid waste. savage beasts took up their abode in the temple, and since then, in spite of the great size of the giants, they have not dared to venture here. if we brave the animals we may have all the gold and diamonds we can take away.”

“then for one, i’m willin’ t’ go down an’ begin th’ extermination at once,” put in andy. “i’ve always wanted t’ be rich.”

“we must proceed cautiously,” the professor said. “we are ill prepared to fight any such beasts as we saw at the big geyser. at the same time they may have deserted this place. i think we will lower the ship down over the temple, and spend several hours in observation. then, if nothing develops, we can enter and see if the treasure is there.”

this plan was voted a good one, and the mermaid after having been steered directly over the ruined temple, was brought to a halt, and enough gas let out so that it fell to about fifty feet in the air above it.

the adventurers began their watch. the afternoon waned and there were no signs of any beasts in or about the temple.

“i reckon we can take a chance,” said andy, who was anxious to get his hands on some diamonds.

“better wait until morning,” counseled mr. henderson. “it will soon be dark, and it doesn’t look like a nice place to go stumbling about in by moonlight.”

so, though all but the scientist were anxious, they had to wait until the night had passed. several times washington got up to see if the temple had, by any chance, taken wings during the long hours of darkness, but each time he found it was still in place.

“seems laik it’ll never come mornin’,” he said.

but dawn came at length, and, after a hasty breakfast, preparations to enter the temple were made. andy loaded his gun for “bear” as he expressed it, and the boys each took a revolver.

the ship was lowered to as level a place as could be found, and then, seeing that everything was in readiness for a quick departure, the professor led the way out of the mermaid.

the entrance to the temple was through a big arched gateway. some of the stones had fallen down, and the whole structure looked as if it might topple over at any moment.

“go carefully,” cautioned mr. henderson. “watch on all sides and up above. better let andy and me go ahead.”

the scientist and the old hunter led the way. through the arch they went, and emerged into what must at one time have been a magnificent courtyard. before them was the temple proper, a vast structure, with an opening through which fifty men might have marched abreast. but the doors were gone, and the portal was but a black hole.

“i hope there ain’t any ghosts in there,” said washington, with a shiver.

“nonsense!” exclaimed the professor. “there may be things as bad, but there are no such things as ghosts. have your gun ready, andy.”

with every sense on the alert, the old hunter advanced. every one was a bit nervous, and, as mark and jack afterward admitted, they half expected some terrible beast to rush out at them. but nothing of the kind happened, and they went into the interior of the temple.

at first it was so dark they could see nothing. there were vast dim shapes on every side, and from the hollow echo of their footsteps they judged the roof must be very high and the structure big in every way.

then, as their eyes became used to the darkness, they could make out, up front, something like an altar or pulpit.

“perhaps that’s where they offered up the gold and diamonds as a sacrifice to their gods,” spoke mark in a whisper.

“sacrifice to their gods!” came back a hundred echoes and the sound made every one shudder.

“oh!” said washington, in a low voice.

“oh! oh! oh!” repeated the echoes in voices of thunder.

“well, this is pleasant,” spoke andy, in his natural tones, and, to the surprise of all there was no echo. it was only when a person whispered or spoke low that the sound was heard. after that they talked naturally.

“you stay here, and andy and i will go up front and see what there is,” said mr. henderson. “be on your guard, and if you hear us coming back in a hurry, run!”

it was with no little feeling of nervousness that the boys, bill, tom and washington watched the two men move off in the darkness. they could hear their footsteps on the stone flags and could dimly see them.

“they must be almost to the altar by this time,” said mark, after a long pause.

hardly had he spoken than there came a loud sound from where mr. henderson and andy had gone. it was as if some giant wings were beating the air. then came shrill cries and the voice of the old hunter could be heard calling:

“kneel down, professor! let me get a shot at the brute!”

those waiting in the rear of the temple huddled closer together. what terrible beast could have been aroused?

the next instant the place seemed illuminated as if by a lightning flash, and a sound as of a thousand thunder claps resounded.

“i think i winged him!” cried andy’s voice, and the boys knew he had fired at something.

then there came a crash, and from the roof of the old temple a dozen stones toppled off to one side, letting in a flood of colored light.

by this illumination could be seen, flapping through the big space overhead, an enormous bat, as large as three eagles. and, as it flew about in a circle it gave utterance to shrill cries.

“bang!” andy’s gun spoke again, and the bat with a louder cry than before, darted through the hole in the roof made by the falling stones, which had been loosened by the concussion from the rifle.

“come on!” cried the old hunter. “that was the guardian of the treasure! we are safe now!”

then, in the light which streamed through the broken roof, the adventurers could see, heaped up on a great altar, behind which sat a horrible graven image, piles of yellow metal, and sparkling stones. in little heaps they were, arranged as if offerings to the terrible god of the giants. there were bars and rings of gold, dishes of odd shape, and even weapons. as for the sparkling stones, they were of many colors, but the white ones were more plentiful than all the others.

“gold and diamonds! diamonds and gold!” murmured the professor. “there is the ransom of many kings in this ancient temple.”

“wish i had a big bag!” exclaimed washington, as he began filling all his pockets with the precious metal and gems. “if i had a-thought i’d have brought a dress-suit case!”

“a dress-suit case full of diamonds!” exclaimed mark.

then he too, as did all the others, fell to filling his pockets with the wealth spread so lavishly before them. there was the riches of a whole world in one place and no one but themselves to take it.

for several minutes no one spoke. the only sound was the rattle of the stones and the clink of gold, and when some of the diamonds dropped on the floor they did not bother to gather them up. there were too many on the altar.

“we will be rich for life!” gasped old andy, who had been poor all his years.

“i can’t carry any more!” gasped washington. “i’m goin’ back for——”

what he was going back for he never said, for, at that instant, happening to look up at the hole in the roof, he gave a startled cry:

“here come the terrible bats!”

they all gazed upward. through the opening they could see a great flock of the awful birds, headed for the temple, and they were led by one which seemed to fly with difficulty. it was the guardian of the treasure that andy had wounded.

“quick! we must get out of here!” shouted the old hunter. “they are big enough and strong enough to tear us all to pieces. hurry!”

down the centre of the temple they rushed, and not a moment too soon, for, ere they had passed half way to the entrance, the opening in the roof was darkened by the coming of the bats, and soon the flapping of their wings awoke the thundering echoes in the ruined structure, while their shrill cries struck terror to the hearts of the travelers.

up to the altar circled the bats, and then wheeling they flapped down the dim aisles toward the adventurers.

“hurry! hurry!” shouted andy, who was in the rear.

he raised his rifle and fired several shots into the midst of the terrible creatures.

a number of the bats were wounded, and the others were so frightened by the sound of the shots and the flashes of fire that they turned back. this enabled the fleeing ones to gain the entrance to the temple, and soon they were outside.

“to the ship!” yelled bill.

“there’s little danger now!” called andy, panting, for the run had winded him. “they will hardly attack us in the light!”

and he was right, for, though they could hear the bats flying about inside the temple, and uttering their cries, none came outside.

but no one felt like staying near the uncanny structure, and little time was lost in reaching the mermaid. then the doors were fastened, and the ship was sent high up into the air.

“which way?” asked jack, when mr. henderson told him to go to the conning tower and steer.

“back to where we first met the giants,” replied the professor. “we must prepare to start for our own earth again soon.”

“i’ve almost forgotten how real sunlight looks,” thought jack, as he headed the ship around the other way. as he turned the levers a big diamond dropped from his pocket and rolled on the floor.

“this will be a good reminder of our trip though,” he added.

the travelers, even including mr. henderson, were so taken up with their suddenly acquired riches that they hardly thought of meals. at the professor’s suggestion they tied their gold and stones up in small packages convenient to carry.

“better place them where you can grab them in a hurry in case of accident,” the old scientist went on. “of course if there should be too bad an accident they would never be of any use to us down here, but we’ll look on the bright side of things.”

“do you anticipate any accident?” asked jack anxiously.

“no, oh no,” replied mr. henderson, but jack thought the aged man had something weighing on his mind.