our young adventurer had intended to pass the night in the little bed at his hotel, but the atmosphere of paris proved so hot and disagreeable that he decided it would be more enjoyable to sleep while journeying through the cooler air that lay far above the earth's surface. so just as the clocks were striking the midnight hour rob mounted skyward and turned the indicator of the traveling machine to the east, intending to make the city of vienna his next stop.

he had risen to a considerable distance, where the air was remarkably fresh and exhilarating, and the relief he experienced from the close and muggy streets of paris was of such a soothing nature that he presently fell fast asleep. his day in the metropolis had been a busy one, for, like all boys, he had forgotten himself in the delight of sight-seeing and had tired his muscles and exhausted his strength to an unusual degree.

it was about three o'clock in the morning when rob, moving restlessly in his sleep, accidently touched with his right hand the indicator of the machine which was fastened to his left wrist, setting it a couple of points to the south of east. he was, of course, unaware of the slight alteration in his course, which was destined to prove of serious importance in the near future. for the boy's fatigue induced him to sleep far beyond daybreak, and during this period of unconsciousness he was passing over the face of european countries and approaching the lawless and dangerous dominions of the orient.

when, at last, he opened his eyes, he was puzzled to determine where he was. beneath him stretched a vast, sandy plain, and speeding across this he came to a land abounding in luxuriant vegetation.

the centrifugal force which propelled him was evidently, for some reason, greatly accelerated, for the scenery of the country he was crossing glided by him at so rapid a rate of speed that it nearly took his breath away.

"i wonder if i've passed vienna in the night," he thought. "it ought not to have taken me more than a few hours to reach there from paris."

vienna was at that moment fifteen hundred miles behind him; but rob's geography had always been his stumbling block at school, and he had not learned to gage the speed of the traveling machine; so he was completely mystified as to his whereabouts.

presently a village having many queer spires and minarets whisked by him like a flash. rob became worried, and resolved to slow up at the next sign of habitation.

this was a good resolution, but turkestan is so thinly settled that before the boy could plan out a course of action he had passed the barren mountain range of thian-shan as nimbly as an acrobat leaps a jumping-bar.

"this won't do at all!" he exclaimed, earnestly. "the traveling machine seems to be running away with me, and i'm missing no end of sights by scooting along up here in the clouds."

he turned the indicator to zero, and was relieved to find it obey with customary quickness. in a few moments he had slowed up and stopped, when he found himself suspended above another stretch of sandy plain. being too high to see the surface of the plain distinctly he dropped down a few hundred feet to a lower level, where he discovered he was surrounded by billows of sand as far as his eye could reach.

"it's a desert, all right," was his comment; "perhaps old sahara herself."

he started the machine again towards the east, and at a more moderate rate of speed skimmed over the surface of the desert. before long he noticed a dark spot ahead of him which proved to be a large body of fierce looking men, riding upon dromedaries and slender, spirited horses and armed with long rifles and crookedly shaped simitars.

"those fellows seem to be looking for trouble," remarked the boy, as he glided over them, "and it wouldn't be exactly healthy for an enemy to get in their way. but i haven't time to stop, so i'm not likely to get mixed up in any rumpus with them."

however, the armed caravan was scarcely out of sight before rob discovered he was approaching a rich, wooded oasis of the desert, in the midst of which was built the walled city of yarkand. not that he had ever heard of the place, or knew its name; for few europeans and only one american traveler had ever visited it. but he guessed it was a city of some importance from its size and beauty, and resolved to make a stop there.

above the high walls projected many slender, white minarets, indicating that the inhabitants were either turks or some race of mohammedans; so rob decided to make investigations before trusting himself to their company.

a cluster of tall trees with leafy tops stood a short distance outside the walls, and here the boy landed and sat down to rest in the refreshing shade.

the city seemed as hushed and still as if it were deserted, and before him stretched the vast plain of white, heated sands. he strained his eyes to catch a glimpse of the band of warriors he had passed, but they were moving slowly and had not yet appeared.

the trees that sheltered rob were the only ones without the city, although many low bushes or shrubs grew scattering over the space between him and the walls. an arched gateway broke the enclosure at his left, but the gates were tightly shut.

something in the stillness and the intense heat of the mid-day sun made the boy drowsy. he stretched himself upon the ground beneath the dense foliage of the biggest tree and abandoned himself to the languor that was creeping over him.

"i'll wait until that army of the desert arrives," he thought, sleepily. "they either belong in this city or have come to capture it, so i can tell better what to dance when i find out what the band plays."

the next moment he was sound asleep, sprawling upon his back in the shade and slumbering as peacefully as an infant.

and while he lay motionless three men dropped in quick succession from the top of the city wall and hid among the low bushes, crawling noiselessly from one to another and so approaching, by degrees, the little group of trees.

they were turks, and had been sent by those in authority within the city to climb the tallest tree of the group and discover if the enemy was near. for rob's conjecture had been correct, and the city of yarkand awaited, with more or less anxiety, a threatened assault from its hereditary enemies, the tatars.

the three spies were not less forbidding in appearance than the horde of warriors rob had passed upon the desert. their features were coarse and swarthy, and their eyes had a most villainous glare. old fashioned pistols and double-edged daggers were stuck in their belts and their clothing, though of gorgeous colors, was soiled and neglected.

with all the caution of the american savage these turks approached the tree, where, to their unbounded amazement, they saw the boy lying asleep. his dress and fairness of skin at once proclaimed him, in their shrewd eyes, a european, and their first thought was to glance around in search of his horse or dromedary. seeing nothing of the kind near they were much puzzled to account for his presence, and stood looking down at him with evident curiosity.

the sun struck the polished surface of the traveling machine which was attached to rob's wrist and made the metal glitter like silver. this attracted the eyes of the tallest turk, who stooped down and stealthily unclasped the band of the machine from the boy's outstretched arm. then, after a hurried but puzzled examination of the little instrument, he slipped it into the pocket of his jacket.

rob stirred uneasily in his sleep, and one of the turks drew a slight but stout rope from his breast and with gentle but deft movement passed it around the boy's wrists and drew them together behind him. the action was not swift enough to arouse the power of repulsion in the garment of protection, but it awakened rob effectually, so that he sat up and stared hard at his captors.

"what are you trying to do, anyhow?" he demanded.

the turks laughed and said something in their own language. they had no knowledge of english.

"you're only making fools of yourselves," continued the boy, wrathfully. "it's impossible for you to injure me."

the three paid no attention to his words. one of them thrust his hand into rob's pocket and drew out the electric tube. his ignorance of modern appliances was so great that he did not know enough to push the button. rob saw him looking down the hollow end of the tube and murmured:

"i wish it would blow your ugly head off!"

but the fellow, thinking the shining metal might be of some value to him, put the tube in his own pocket and then took from the prisoner the silver box of tablets.

rob writhed and groaned at losing his possessions in this way, and while his hands were fastened behind him tried to feel for and touch the indicator of the traveling machine. when he found that the machine also had been taken, his anger gave way to fear, for he realized he was in a dangerously helpless condition.

the third turk now drew the record of events from the boy's inner pocket. he knew nothing of the springs that opened the lids, so, after a curious glance at it, he secreted the box in the folds of his sash and continued the search of the captive. the character marking spectacles were next abstracted, but the turk, seeing in them nothing but spectacles, scornfully thrust them back into rob's pocket, while his comrades laughed at him. the boy was now rifled of seventeen cents in pennies, a broken pocket knife and a lead-pencil, the last article seeming to be highly prized.

after they had secured all the booty they could find, the tall turk, who seemed the leader of the three, violently kicked at the prisoner with his heavy boot. his surprise was great when the garment of repulsion arrested the blow and nearly overthrew the aggressor in turn. snatching a dagger from his sash, he bounded upon the boy so fiercely that the next instant the enraged turk found himself lying upon his back three yards away, while his dagger flew through the air and landed deep in the desert sands.

"keep it up!" cried rob, bitterly. "i hope you'll enjoy yourself."

the other turks raised their comrade to his feet, and the three stared at one another in surprise, being unable to understand how a bound prisoner could so effectually defend himself. but at a whispered word from the leader, they drew their long pistols and fired point blank into rob's face. the volley echoed sharply from the city walls, but as the smoke drifted slowly away the turks were horrified to see their intended victim laughing at them.

uttering cries of terror and dismay, the three took to their heels and bounded towards the wall, where a gate quickly opened to receive them, the populace feeling sure the tatar horde was upon them.

nor was this guess so very far wrong; for as rob, sitting disconsolate upon the sand, raised his eyes, he saw across the desert a dark line that marked the approach of the invaders.

nearer and nearer they came, while rob watched them and bemoaned the foolish impulse that had led him to fall asleep in an unknown land where he could so easily be overpowered and robbed of his treasures.

"i always suspected these electrical inventions would be my ruin some day," he reflected, sadly; "and now i'm side-tracked and left helpless in this outlandish country, without a single hope of ever getting home again. they probably won't be able to kill me, unless they find my garment of repulsion and strip that off; but i never could cross this terrible desert on foot and, having lost my food tablets, i'd soon starve if i attempted it."

fortunately, he had eaten one of the tablets just before going to sleep, so there was no danger of immediate starvation. but he was miserable and unhappy, and remained brooding over his cruel fate until a sudden shout caused him to look up.