professor swyington bumper seemed to live in a region all by himself. though he was on board the bellaconda, he might just as well have been in an airship, or riding along on the back of a donkey, as far as his knowledge, or recognition, of his surroundings went. he seemed to be thinking thoughts far, far away, and he was never without a book—either a bound volume or a note-book. in the former he buried his hawk-like nose, and tom, looking over his shoulder once, saw that the book was printed in curious characters, which, later, he learned were sanskrit. if he had a note-book the bald-headed professor was continually jotting down memoranda in it.

"i can hardly think of him as a conspirator against us," said tom to mr. titus.

"after you have been in the contracting business as long as i have you'll distrust every one," was the answer. "waddington isn't on board, or i'd distrust him. that spaniard, senor pinto, seems to be out of consideration, and there only remains the professor. we must watch him."

but professor bumper proved to be above suspicion. carefully guarded inquiries made of the captain, the purser and other ships' officers, brought out the fact that he was well known to all of them, having traveled on the line before.

"he is making a search for something, but he won't say what it is," the captain said. "at first we thought it was gold or jewels, for he goes away off into the andes mountains, where both gold and jewels have been found. he never looks for treasure, though, for though some of his party have made rather rich discoveries, he takes no interest in them."

"what is he after then?" asked mr. titus.

"no one knows, and he won't tell. but whatever it is he has never found it yet. always, when he comes back, unsuccessful, from a trip to the interior and goes back north with us, he will remark that he has not the right directions. that he must seek again.

"back he comes next season, as full of hope as before, but only to be disappointed. each time he goes to a new place in the mountains where he digs and delves, so members of the parties he hires tell me, but with no success. he carries with him something in a small iron box, and, whatever this is, he consults it from time to time. it may be directions for finding whatever he is after. but there seems to be something wrong."

"this is quite a mystery," remarked tom.

"it certainly is. but professor bumper is a fine man. i have known him for years."

"this seems to dispose of the theory that he planted the bomb, and that he is one of the plotters in the pay of blakeson & grinder," said mr. titus, when he and tom were alone.

"yes, i guess it does. but who can have done it?"

that was a question neither could answer.

tom had a theory, which he did not disclose to mr. titus, that, after all, the somewhat mysterious senor pinto might, in some way, be mixed up in the bomb attempt. but a close questioning of the steward on duty near the foreigner's cabin at the time disclosed the fact that pinto had been ill in his berth all that day.

"well, unless the bomb fell from some passing airship, i don't see how it got on deck," said tom with a shake of his head. "and i'm sure no airship passed over us."

they had kept the matter secret, not telling even mr. damon, for they feared the eccentric man would make a fuss and alarm the whole vessel. so mr. damon, occasionally blessing his necktie or his shoe laces, played chess with his elderly gentleman friend and was perfectly happy.

that professor bumper not only had kept his promise about not mentioning the bomb, but that he had forgotten all about it, was evident a day or two after the happening. tom and mr. titus passed him on deck, and bowed cordially. the professor returned the salutation, but looked at the two in a puzzled sort of fashion.

"i beg your pardon," he remarked, "but your faces are familiar, though i cannot recall your names. haven't i seen you before?"

"you have," said tom, with a smile. "you saved our lives from a bomb the other day."

"oh, yes! so i did! so i did!" exclaimed professor bumper. "i felt sure i had seen you before. are you all right?"

"yes. there haven't been any more bombs thrown at us," the contractor said. "by the way, professor bumper, i understand you are quite a traveler in the andes, in the vicinity of lima."

"yes, i have been there," admitted the bald-headed scientist in guarded tones.

"well, i am digging a tunnel in that vicinity," went on mr. titus, "and if you ever get near rimac, where the first cutting is made, i wish you would come and see me—tom too, as he is associated with me."

"rimac-rimac," murmured the professor, looking sharply at the contractor. "digging a tunnel there? why are you doing that?" and he seemed to resent the idea.

"why, the peruvian government engaged me to do it to connect the two railroad lines," was the answer. "do you know anything about the place?"

"not so much as i hope to later on," was the unexpected answer. "as it happens i am going to rimac, and i may visit your tunnel."

"i wish you would," returned mr. titus.

later on, in their stateroom, the contractor remarked to the young inventor:

"sort of queer; isn't it?"

"what?" asked tom. "his not remembering us?"

"no, though that was odd. but i suppose he is forgetful, or pretends to be. i mean it's queer he is going to rimac."

"what do you mean?" asked tom.

"well, i don't know exactly what i mean," went on the tunnel contractor, "but our tunnel happens to start at rimac, which is a small town at the base of the mountains."

"maybe the professor is a geologist," suggested tom, "and he may want to get some samples of that hard rock."

"maybe," admitted mr. titus. "but i shall keep my eyes on him all the same. i'm not going to have any strangers, who happen to be around when bombs drop near us, get into my tunnel."

"i think you're wrong to doubt professor bumper," tom said.

a few days after this, when tom and mr. titus were casually discussing the weather on deck and wondering how much longer it would be before they reached callao, mr. damon, who had been playing numberless games of chess, came up for a breath of air.

"mr. damon," called tom, "come over here and meet a friend of ours, professor bumper," and he was about to introduce them, for the two, as far as tom knew, had not yet met. but no sooner had the professor and mr. damon caught sight of each other than there was a look of mutual recognition.

"bless my fountain pen!" cried the eccentric man. "if it isn't my old friend!"

"mr. damon!" cried the professor. "i am delighted to see you again. i did not know you were on board!"

"nor i you. bless my apple dumpling! are you still after those peruvian antiquities?"

"i am, mr. damon. but i did not know you were acquainted with mr. swift."

"oh, tom and i are old friends."

"professor bumper saved the lives of mr. titus and myself," said tom, "or at least he saved us from severe injury by a bomb."

"pray do not mention it, my friends," put in the professor, casually. "it was nothing."

of course he did not mean it just that way.

then, naturally, mr. damon had to be told all about the bomb for the first time, and his wonder was great. he blessed everything he could think of.

"and to think it should be my old friend, professor bumper, who saved you," said the odd man to tom and mr. titus later that day.

"do you know him well?" asked mr. titus.

"very well indeed. our drug concern sells him many chemicals for his experiments."

"well, if you know him i guess he can't be what i thought he was," the contractor went on. "i'm glad to know it. why is he going to the andes?"

"oh, for many years he has been interested in collecting peruvian antiquities. he has a certain theory in regard to something or other about their ancient civilization, but just what it is i have, at this moment, forgotten. only i know you can thoroughly trust professor bumper, for a finer man never lived, though he is a bit absent-minded at times. but you will like him very much."

thus the last lingering doubt of professor bumper was removed. mr. damon told something of how the scientist had been honored by degrees from many colleges and was regarded as an authority on peruvian matters.

but who had placed the bomb on deck remained a mystery.

in due time callao, the seaport of lima, was reached and our friends disembarked. tom saw to the unloading of the explosive, which was to be sent direct to the tunnel at rimac. mr. titus, tom and mr. damon would remain in lima a day or so.

professor bumper disembarked with our friends, and stopped at the same hotel. tom kept a lookout for senor pinto, but did not see him, and concluded that the spaniard was ill, and would be carried ashore on a stretcher, perhaps.

lima, the principal city and capital of peru, proved an interesting place. it was about eight miles inland and was built on an arid plain about five hundred feet above sea level. yet, though it was on what might be termed a desert, the place, by means of irrigation, had been made into a beauty spot.

tom found the older part of the city was laid out with mathematical regularity, each street crossing the other at right angles. but in the new portions there was not this adherence to straightness.

"bless my transfer! why, they have electric cars here!" exclaimed mr. damon, catching sight of one on the line between callao and the capital.

"what did you think they'd have?" asked mr. titus, "elephants or camels?"

"i—i didn't just know," was the answer.

"oh, you'll find a deal of civilization here," the contractor said. "of course much of the population is negro or indian, but they are often rich and able to buy what they want. there is a population of over 150,000, and there are two steam railroads between callao and lima, while there is one running into the interior for 130 miles, crossing the andes at an elevation of over three miles. it is a branch of that road, together with a branch of the one running to ancon, that i am to connect with a tunnel."

tom found some beautiful churches and cathedrals in lima, and spent some time visiting them. he and mr. damon also visited, in the outskirts, the tobacco, cocoa and other factories.

three days after reaching the capital, mr. titus having attended to some necessary business while mr. damon set on foot matters connected with his affairs, it was decided to strike inland to rimac, and to try the effect of tom swift's explosive on the tunnel.

the journey was to be made in part by rail, though the last stages of it were over a rough mountain trail, with llamas for beasts of burden, while our friends rode mules.

as tom, mr. damon, koku, and mr. titus were going to the railroad station they saw professor bumper also leaving the hotel.

"i believe our roads lie together for a time," said the bald-headed scientist, "and, if you have no objections, i will accompany you."

"come, and welcome!" exclaimed mr. titus, all his suspicions now gone.

"and it may be that you will be able to help me," the scientist went on.

"help you—how?" asked tom.

"i will tell you when we reach the andes," was the mysterious answer.

it was a day later when they left the train at a small station, and struck off into the foothills of the great andes mountains, where the tunnel was started, that the professor again mentioned his object.

"friends," he said, as he gazed up at the towering cliffs and crags, "i am searching for the lost city of pelone, located somewhere in these mountains. will you help me to find it?"