ending more  and  more  of his time in Koltukhov's
resin  laboratory.  He liked  making new  compounds according to Koltukhov's
formulas and measuring the electricity in the charged resins.
     One day Koltukhov sent Yura  over to Opratin's laboratory to charge the
latest batch of resin.
     Opratin  greeted Yura pleasantly, showed him the electrostatic machine,
and helped him to switch it on.
     Yura  looked about with curiosity. There were several  people  in white
overalls  at  work in the laboratory. One of  them, a thickset  man  with  a
shaggy  head of hair, sat  with his  back  to Yura, at  a table  on which an
aquarium with  a wire coil round it  and a valve  oscillator stood. "Are you
doing high frequency experiments?" he asked casually.
     "Oh, that's just a minor project," Opratin replied  with a  keen glance
at Yura. "Are you interested in high frequencies?" "No, not particularly."
     A tall, husky man  in  blue overalls entered the laboratory. To  Yura's
surprise, this was Uncle Vova Bugrov.
     "Comrade  Benedictov,  here's  the food for your fish," Bugrov  said to
Anatole Benedictov in a deep, hoarse voice.
     The shaggy-haired man sitting beside the valve oscillator turned round,
nodded, and took the two paper  bags Bugrov was holding out to him. Yura was
unable to shift his gaze from the man's broad face and puffy eyelids.
     "Why, hullo," said Bugrov shaking Yura's hand. "What brings  you to our
Institute?"
     "Do  you work here?"  Yura  asked in surprise, his  eyes still fixed on
Benedictov.
     "I'm a laboratory technician. I've switched to science now.  They think
very highly of me here. You know, I'm training a group of scientific workers
in wrestling."
     "What does Benedictov do here?" Yura asked in a low voice.
     "Benedictov?  He's a  scientist. He knows all there  is  to know  about
fish. Shall I tell you what else  I'm doing?" Bugrov asked boastfully.  "I'm
an inventor, if you want to know. I'm making an  electric  dynamometer. What
d'you think of that?"
     After charging  the resin Yura rushed back to his own Institute and ran
up the stairs two at a time.
     "There's  news, Nikolai," he shouted.  Panting,  he told  Nikolai about
seeing Benedictov, about the valve oscillator and about Vova Bugrov.
     Nikolai ran the  palm  of his  hand  across  his  high  forehead. "High
frequency-  and fish? I  wonder- But  Opratin is  studying the  level of the
Caspian, isn't he?"
     "Benedictov's the man to ask about the iron boxes."
     "You think he'd tell you?"
     During  the  lunch  break Nikolai  remained in the deserted laboratory.
Sitting at his desk,  he cut a thin strip from the sheet of drawing paper on
his board. He pinned one end to the desk, twisted  the other in a half-curl,
and glued the ends together.
     He sat for a long time  staring, in deep thought, at the twisted  piece
of paper.  Then, with  a pencil, he  drew a line along the edge of the paper
until  it came full  circle. The line ran round  both sides of the  strip of
paper, without Nikolai  either lifting his pencil from the paper or crossing
the  pencil  line at  any point.  This  strip of paper  was the  model  of a
mathematical paradox known as the Mobius band. From  the mathematical  point
of view the band had no thickness and its surface was not divided into outer
and inner surfaces.  It was only a surface, and nothing more. A window  that
mathematics had opened up into the sphere of the Unknown.
     Nikolai made a second strip twisted in the same direction  and tried to
put it inside the first one, but  this proved to be impossible. By trying to
put one strip into another he  would have to  bring the inner surface of one
towards the outer  surface of the other. But if neither had an outer surface
or an inner surface how could he do this?
     Nikolai  flung the strips on the table  and  propped up his head on his
hand. "What if I made a similar spiral out of copper and linked it up to the
output circuit of an oscillator?"
     He went  out  to the lounge,  pulled Yura  away from  a  game  of table
tennis, and said: "Do you remember a thing called the Mobius band?"


        CHAPTER THREE

        IN WHICH THE SAME BRIGHT IDEA,
     NECESSITATING FEDOR MATVEYEV'S KNIFE,
     OCCURS TO BENEDICTOV AND OPRATIN

     "At last!" Opratin exclaimed, running his eyes across the letter, which
was typed on an official letterhead.
     Ever since summer, Opratin's imagination had been fired by the  letters
A M  D G on  Benedictov's box  that  had  contained  the missing knife. When
Benedictov  showed  him the box  Opratin  had immediately recalled  the  old
underground  passage in Derbent, the crucifix on the  chest of the skeleton,
and, lying beside it, the small flat box on a golden chain, with the letters
A M D G engraved on it.
     From what Pavel Koltukhov had  said  Opratin  now knew that  there were
three boxes, and that the third box, the one in Derbent, contained some sort
of "key to the mystery".
     Opratin had written  a number of cautious letters, first to Derbent and
then to Moscow,  after  learning that  the  agent's equipment had been  sent
there.  Now the  long-awaited reply was in his hands. The  agent had been  a
submarine officer  in the Italian Tenth Torpedo-Boat Flotilla, notorious for
its sudden raids on British naval bases with mines guided by frogmen.
     Part of the Tenth Flotilla had been transferred  to the Crimea in 1942.
When the Nazis broke through to the North Caucasus  part of the Flotilla had
concentrated submarines and frogmen-guided torpedoes  at Mariupol on the Sea
of Azov for transfer to the Caspian Sea.
     Vittorio  da Castiglione,  an officer of the Tenth Flotilla, parachuted
down onto the Caspian coast near Derbent on a dark autumn night. His mission
had  probably been to reconnoitre the underwater  approaches to  the port of
Derbent and note installations that could be attacked with guided torpedoes.
But he had wandered into an old  quarry and had perished there. Nobody would
ever have learned about Vittorio da Castiglione if Opratin  had not stumbled
over him.
     "To recapitulate," Opratin said  to  himself,  "one box contained Fedor
Matveyev's manuscript and another the knife. But what was  in the third box?
Probably  something  very important  that  would throw light  on the  entire
mystery."
     Well, he'd soon know what it was all about.
     Nikolai Opratin rubbed his hands in satisfaction.
     The  Institute  of Marine Physics was  making preparations to raise the
level of the Caspian Sea. This undertaking was based on the extremely simple
proposition  that a heavy  rain  can produce one and a half  millimetres  of
precipitation  in one  minute. If rain poured down constantly on  an area of
thirty square kilometres of the Caspian day in and day out, the level of the
sea would rise three metres in the course of a year. Water for the downpours
would have  to be "borrowed" from the Black Sea, where there  were  plans to
build  a  powerful nuclear water boiler.  A new  Soviet method of  obtaining
nuclear energy made such an installation possible.
     As a  gigantic fountain of steam gushed  forth from  the depths of  the
Black Sea  a  system of  directional antennae would  force the endless  grey
cloud to snake its way over the Caucasus Mountains. On reaching the downpour
area in  the  Caspian  Sea the  cloud would  enter  the  zone  of a powerful
electrostatic field.  Here the concentrated  steam would  lose its  heat, be
converted into water, and pour down on the sea.
     Laboratory  No. 8 was  setting up  cloud condensation  experiments, and
this  kept  Opratin,  as  head  of  the laboratory,  very  busy  indeed. The
installation had given  him  a good  many  sleepless nights. Erection of the
installation on  a remote,  uninhabited  island  in the Caspian  was nearing
completion.  Opratin was personally  supervising  the operations. He  had in
mind certain other plans that were linked up with this installation.
     The two new members of the staff  introduced  a somewhat  disharmonious
note  into  the  carefully  planned  arrangements in  Opratin's  laboratory.
Shaggy-haired,  absent-minded  Anatole  Benedictov  spilled  reagents   from
bottles  on the tables, broke a  great many vessels and  often caused  short
circuits. He argued  with Opratin in a loud voice.  Yet Opratin  was patient
with him, and this was what aroused the greatest astonishment.
     With Benedictov's arrival  the "fish  problem" suddenly loomed large in
the Institute programme. At any rate, it occupied all the best places in the
corridors, for that was  where Anatole Benedictov had set  up his aquariums.
He plagued  the  assistant manager in charge of  supplies with  demands  for
various types of food for his fish.
     Feeding  the fish  was one of  the duties of the new lab technician,  a
husky, rosy-cheeked man with  slits for eyes and  a  tuft of reddish hair on
top  of his  head. This was Vova Bugrov. Bugrov very soon felt quite at home
in the  world  of  scientific research. As one watched  him  puttering about
beside the spectrograph, softly humming  a popular tune, one  felt  that the
delicate cassettes were doomed.
     "I wonder why Opratin ever  took this chap on as  a technician,"  staff
members  asked one another.  "He  looks  more like  a gangster than anything
else."
     To everyone's surprise, though, the new technician turned out to have a
light touch;  his  huge  paws handled  the  precise  instruments  gently and
deftly. Bugrov could do a marvellous soldering job. He put great effort into
developing  the spectrograms, and he  kept a detailed journal (with spelling
mistakes in it, true) of the functioning of the various lab instruments  and
machines. This was more than even Opratin had expected from Bugrov.
     The motorboat skimmed across the bay towards the open sea.  Prow lifted
high, it left behind a pair  of long, spreading, foamy moustaches.  It was a
calm, sunny morning in October, with a slight chill in the air.
     Bugrov, his cap pulled down over his forehead, sat  beside the outboard
motor. Suddenly he pricked up his ears.  Above the  steady roar of the motor
he caught snatches of an interesting conversation.
     "No, I don't think they know about the knife," said Nikolai Opratin.
     "Then why did they come asking to see me?" Anatole Benedictov retorted.
"They  asked  questions, Rita says,  about three small iron  boxes. But  why
three?  One  contained  the  knife; in  the other,  you say,  they  found  a
manuscript. But where does a third box come from?"
     "That's my business."
     Opratin wrapped his raincoat more closely round him.  Benedictov  tried
to light a cigarette but every  time he struck a match the wind blew it out.
He swore as he kept tossing matches into the water.
     On reaching the island  they guided the boat into  a cove with a gently
sloping  shore.  Bugrov cut the  motor and nimbly jumped out  onto  the damp
sand. He tied the painter to a length of pipe he had driven into the sand on
an earlier visit to the island.
     Here, on this desolate little island, Laboratory No. 8 of the Institute
of Marine Physics had set up an experiment facility.
     Two months ago  a blunt-nose self-propelled barge  had pulled its  flat
belly up onto the sandy shore, and a tractor, followed by a crane on crawler
treads, had rolled out of its dark interior with much clanging.
     An  old concrete  pillbox built on the island  during the war  had been
converted into a pilot plan for cloud condensation.
     Benedictov and Opratin climbed to the top of the low but steep rise and
disappeared  inside the former pillbox. Bugrov  remained  on  the  shore. He
walked up and down the sand for a while to  stretch his legs,  then sat down
on a rock to think.
     There  was plenty  to  think  about. For  two  months now  he had  been
punching the clock, something he had never done before in his life- and what
was  he getting out of it?  Where was the  knife for which he  had agreed to
take on the job of lab technician?
     It was  becoming embarrassing. Friends were laughing  at him. A steady,
full-time job, of  all  things!  In  science, too!  It  was time  he gave up
working like a horse, they said.
     Bugrov couldn't have agreed with them more. He would give it up-just as
soon as he finished his dynamometer. It would be a beauty! All you'd have to
do was step on the footboard  and  flex your muscles,  and the machine would
show you how strong you were. There would be no lights or bells, like in the
ordinary dynamometers. This one was strictly scientific.
     All of  a sudden Bugrov grew angry with  himself. What was  he thinking
about?  The  knife  was  what he needed!  Then  he  would  be  able  to tour
provincial towns with an astonishing knife act.
     He scrambled up the rise  and approached the pillbox. After opening the
inclining steel door he entered an underground passageway lined with shelves
holding  storage cells.  The passageway led into a round room  with a  domed
ceiling.  An internal combustion engine  stood there. From  this room Bugrov
passed through a narrow doorway into what had once been the casemate.
     The  room  was crowded  with  laboratory  equipment.  Red-hot filaments
glowed in an electric fireplace. Nikolai  Opratin and Anatole Benedictov sat
at a table under a bright light.
     Bugrov  marched  to the middle  of  the room  and stood there, hands in
pockets, his padded jacket flung open. His face wore an insolent expression.
"You promised me the knife," he said. "When will it be ready?"
     Opratin  drummed his fingers on the  table. "Look here," he said in  an
even voice, "if you  get on my nerves  you'll never lay eyes on the knife at
all. Can't you see we haven't set up all the equipment yet? Be patient."
     "I'm patient,  all  right," Bugrov  replied defiantly. "Too patient, in
fact. I'm just warning you. You'd better speed things up."
     "That will  do. Instead of complaining you could put  your  energies to
better use by tinkering with the power generator. You're the one who will be
servicing it."
     Bugrov pushed his cap to the back of his head and left the room.
     The mutiny on the island had been put down.
     "I can't see why you have anything to do with that gorilla," Benedictov
remarked.
     Opratin  shook  his head. "Rank ingratitude, I call it. That gorilla is
the person who gets you those ampoules you're so fond of."
     Benedictov said nothing.
     "He's right. We'll have to speed things up," Opratin went on. "We won't
be  here alone forever.  We'll have  to start work  on cloud condensation as
well, and that means researchers will be coming here to work. I shan't allow
them to see the equipment in the room below, of course, but still- Anyway, I
have  an  idea." He told Benedictov of his talk  with Pavel Koltukhov, about
the  episode  mentioned  in  Fedor  Matveyev's  manuscript  and   about  the
electrets.
     "Don't you  see?  The Hindus  may very  well have used  electrets as  a
source of energy. Electrets have a peculiar property to which I have given a
great deal of thought."
     "Namely?"
     "A shift  in polarity. Sometimes an electret begins  to lose its charge
within a few hours. The  charge drops to zero and  then increases again, but
now the positive  and negative poles have  changed  places. An electret with
altered poles will exist for an indefinite time. Sometimes this happens  and
sometimes  it doesn't. W7hat changes  take  place  in the substance  of  the
electret? What is this zero threshold across which its charge passes? That's
the question."
     "A magnet magnetizes other substances without losing its properties. An
electret  charges  other   substances  without  losing  its  charge,"   said
Benedictov.  He  was  speaking  with  his eyes closed,  concentrating on his
words. "Splendid!  That confirms  my  idea.  What  we must do is  set up  an
installation in  which the knife will transmit  the charge.  The knife  will
charge  other  bodies  with its  properties, will  remake their structure to
resemble  its  own.  To  put  it  more  exactly,  the  knife  will  transmit
penetrability."
     Opratin stared at Benedictov in silence for a few seconds.
     "Transmit penetrability," he repeated in a low voice. "Use the knife as
a transducer. That's a brainwave!"
     Benedictov coughed to clear his throat and then amplified his idea.
     "It's a brainwave!" Opratin  repeated, striding  up  and down the room.
"Do you mean to say we can do it with living material too?"
     "Exactly. My experiments with fish make me confident of success."
     Opratin  stopped  pacing the floor. "To sum up, we'll make an  electret
with switched polarity that  will create a permanent  field. We'll intensify
the  field with a  powerful  charge of static electricity, using our Van  de
Graaff generator. We'll set up the installation in such a way as to make the
fields intersect. We'll place Fedor Matveyev's knife, the transmitter of the
'charge,' at one intersection and an ultrashort wave radiator at  the other.
It will  be a kind of  cage in which we'll  put some  of your fish, or maybe
dogs.  Or anything else,  for that  matter.  We'll keep  changing  the field
intensity and  keep on  experimenting until we hit on just the right angle!"
Opratin's eyes sparkled. He was so excited that he could hardly stand still.
"Yes, we'll force that knife to transmit its properties to another object!'"
     Arguing and interrupting each  other,  the two  scientists proceeded to
sketch designs of the future  installation.  Suddenly Benedictov flung aside
his pencil and rose, his joints creaking.
     "The  knife," he said. "We must have the knife. We  won't  get anywhere
without it. I don't think you're searching for it the way you should."
     "I've combed the sea floor at that place three times." Opratin stopped,
then added in a lower voice, "Is there any reason why your wife  should want
to hinder our work?"
     "Hinder our work? No, although lately she's  been urging me to drop  my
experiments. But that's all. Why do you ask?"
     ^Because  the knife doesn't seem to be at the bottom of the sea. I have
a feeling your wife is concealing it."
     Benedictov's face grew long. "Impossible. Why should she do that?"
     "Why  should  she  try  to  persuade  you  to  give  up  this  line  of
experiments?"
     Benedictov  did  not reply.  The  electric  fireplace threw red shadows
across his gloomy face.
     "Never mind, you leave the knife to me," Opratin said. "I'll get it."


        CHAPTER FOUR

     IN WHICH VALERY GORBACHEVSKY'S LITTLE FINGER PLAYS THE LEADING PART

     Nikolai and Yura  were now completely engrossed in the enigmatic Mobius
band. Their  catch-all notebook was filled to overflowing with  formulas and
sketches of intertwined bands.
     "Your idea of using one side  is marvellous, Nikolai!" Yura  exclaimed.
"I'm sure the Mobius band will give us the field we need. Imagine! No pipes!
A stream of oil flowing straight through the sea!"
     Yura's enthusiasm was infectious. "I've estimated," Nikolai said, "that
doing away with  pipes to transport oil across  the Caspian would save about
25,000 tons of steel."
     "But that's not the main thing," Yura said impatiently. "We'll learn to
control surfaces. It'll be an epoch-making discovery!"
     "Now don't let our imagination run  away with  you,"  Nikolai remarked.
"We aren't in that class at all. With our limited resources we  can only set
ourselves  a limited goal like increasing  the surface  tension of a drop of
mercury. If we succeed we'll try to do the same with oil."
     Yura grew downcast. "Is that all?"
     "No, not quite. Don't spread this all  over the Institute and don't say
anything, meanwhile, to our chief. Is that clear?"
     "Yes,  strictly confidential," Yura said with  a sigh. "The Inquisition
put the same kind of pressure on Galileo."
     The  evenings in Cooper Lane were now a busier time than ever. Yura and
Nikolai  had  enlisted  the  services  of  three  young  engineers from  the
automation  department, who  helped  them  to assemble  intricate electronic
circuits. They often blew the fuses and then had  to go out with a candle to
repair  the damage. Luckily,  Nikolai's  mother  was a patient, kind-hearted
woman.
     One day lab  technician Valery Gorbachevsky took Yura aside.  "Need any
help evenings?" he asked.
     Yura  stared at him. "How  do you know what we're doing  after  working
hours?"
     "I'm not deaf, am I?"
     "All right, drop in tomorrow at eight. Just keep whatever you see under
your hat. Don't mention it to Privalov. What we're doing at home is  our own
private concern."
     Valery nodded.
     "After all, Faraday was once a lab technician too."
     "Faraday? A lab technician?"
     "That's right. Not  here,  of course, but at  the Royal Institution  of
Great Britain. As you can see, a big future lies ahead of you."
     That evening Yura, a guitar slung  over  his  shoulder, strode  briskly
down Cooper Lane and turned into the courtyard of Nikolai's  house. A series
of what sounded like gunshots came from the other side of the archway, where
a tall, plump woman  was beating a carpet. At sight of Yura she gave a broad
smile. "Haven't seen you for a long time," she said.
     "Good evening, Claudia," said Yura.
     "Is Nikolai throwing a birthday  party?" she asked. "Guests keep coming
and coming. Young people, all of them." She smiled  again. "My Vova is doing
scientific research too nowadays."
     "Well,  give him my best regards."  Yura smiled politely and ran up the
steps two at a time. He flung  open a door from behind which came voices and
laughter. Everyone was there.  Nikolai and the three other  young  engineers
were tinkering with  the instruments. They had the  efficient assistance  of
Valery, who never suspected he was destined to be the hero of the day.
     "What held you up?" asked Nikolai.
     "Uncle  Vova's wife stopped  me  for a chat and asked me to pass on her
very best regards," Yura replied.
     "Why the guitar?"
     "I'll sing you some songs."
     "Stop twaddling. Come on, let's check the connections."
     "I'll tell you  why I brought the guitar." Yura's tone was now serious.
"Our tuning-fork generator is made to oscillate  by  an electromagnet, isn't
it? But the  electromagnet  means an extra magnetic  field, in  other words,
frequencies that we don't need at all. So I thought-"
     "That's right," swarthy  Hussein Amirov  put in. "A guitar  can  do the
work more simply than an electromagnet."
     The installation  stood  on  a  big  table  behind blue  draperies.  It
consisted  of  the  original  mercury heart  and  valve  oscillator  with  a
tuning-fork breaker, to which a twist  of copper tubing, an  enormous Mobius
band, had  been  added.  The output  circuit  of the  valve  oscillator  was
connected to coils  surrounding  the band. The scales containing the mercury
heart stood inside the band.
     The one-sided  Mobius  band was expected to produce a field which would
sharply increase the  surface tension of the  mercury and squeeze it so hard
that it  would  stop  pulsating.  Then, by  adding  mercury  until the heart
started  beating again  they would be able to calculate, from the additional
weight, the extent to which surface  tension had been stepped  up. Once they
hit  on the right combination of  frequencies they could start experimenting
with oil.
     Nikolai switched  on the  battery of  capacitors. To do this he had  to
crawl under the table and disturb Rex, who was sound asleep there.
     As  Yura checked  the  connections the neon  bulb in the  handle of his
screwdriver glowed with a twinkling pink light from time to time.
     "All systems functioning," Yura finally declared. "Breaker frequency is
440 hertz."
     "Ting, ting,  ting" went the tuning-fork gently  in the  silence of the
room.
     Yura hurriedly tuned  his guitar. Next  they  adjusted  the tuning-fork
breaker by moving the weights on its prongs.
     Now all they had to do was touch a guitar 'string,  and the contacts of
the tuning-fork breaker |would begin to break the  high-frequency circuit at
the rate of 440 times per second.
     The mercury  heart  beat quietly  inside  the  mysterious  field of the
Mobius band. Our  experimenters knew, of course, that a long, boring  search
lay ahead  of them. They knew that an experiment  rarely  yields the desired
result  the first  time. Still,  deep  down inside there  was the hope  that
perhaps today a miracle would take place.
     It didn't.
     "We'll  have to vary the  operating  factors,"  said Nikolai. "Will you
strike B on the tuning-fork, Valery?"
     Ting-ting-ting.
     Yura plucked a guitar string.'
     There was silence, broken suddenly by a sharp knock on the door.
     "Who  could that  be?" Nikolai  wondered.'  "Mother  said  she wouldn't
return home until late."
     The young  men moved away from the installation and drew  the draperies
to hide it from view. Only Valery, with  his tuning-fork,  :and Rex remained
behind the draperies.
     "Let's liven up the party!" shouted Yura. He plucked the strings of the
guitar, took a few dancing steps, and began to sing:

     Why do you wander in the moonlight,
     Oh black-eyed beauty of mine?
     Powder in your pocket to poison me with,
     A locomotive in your pocket to crush me with.

     Nikolai opened the door and Vova Bugrov, in a striped  blue pyjama top,
came in.
     "Hullo, everybody," he said politely,  letting his eyes roam  about the
room. His  glance  rested on the blue  draperies  and on the scraps  of wire
scattered  on the floor. Then he shook hands  with each of the  young men in
turn. "Having a party?" he asked.  "That's fine. I'll take  only a minute of
your  time, Nikolai." He  pulled a rusty spring out of his pocket. "Will you
calculate its strength, please?"
     "You said you'd switched to electric dynamometers," said Yura.
     "So I have," Bugrov replied with dignity. "This is just something-well,
to make a long story short, a couple of pals dropped in and asked me to help
them."
     Nikolai quickly measured  the diameter of the spring  and the  wire  to
which it was attached, and then took out his slide-rule.
     "Twenty-eight kilograms."
     "Thanks." Bugrov picked up the spring and moved towards the door.
     At that moment  there was a crash behind the draperies. The  young  men
exchanged glances. Vova swung round and stared at the draperies. Rex emerged
from beneath them, his paws tapping the floor. He stretched and then sniffed
at Bugrov's shoes.
     "Go away,  dog," said Bugrov, backing  towards the door. "I  don't like
being sniffed at."
     Nikolai  saw  Bugrov out and locked  the  door  behind him. Yura struck
another few chords to  be on the  safe  side. Strumming the bass strings, he
sang:

     Powder in your pocket to poison me with,
     A locomotive in your pocket to crush mo with.

     Nikolai pulled back the  draperies. The  scales with the  mercury heart
had crashed  to  the floor.  The tuning-fork  generator  lay  in  a pool  of
solution with sparkling drops of mercury in it. Valery sat on the table, his
face as white as a sheet. He was holding up his  right hand and was  staring
in horror at his extended little finger.


     That  evening  Boris  Privalov and  Pavel  Koltukhov  remained  at  the
Institute long after everyone else had left.
     "If you don't mind my  saying  so,  Boris, you're going round the  bend
about that idea of a pipeline without any pipes," said Koltukhov.
     "Has Professor Bagbanly gone round the bend too?"
     Koltukhov said nothing.
     Privalov looked at his  watch and stood up.  "By  the way, he should be
here soon. Would you like to see what we're doing?"
     They went down to the first floor and walked along  a seemingly endless
corridor. Privalov unlocked the doors of a room in which a stator from a big
dynamo  stood.  Inside  the  stator,  almost  touching  the  pole  shoes and
windings, was a coil of glass tubing filled with a pink liquid. The ends  of
the coil were connected with a tank and a centrifugal pump.
     "It looks like a high-frequency  still  for making  home-brew  liquor,"
Koltukhov said  with a laugh, touching the cold  glass with the  tips of his
fingers.
     "We're doing two experiments  with this apparatus," Privalov explained.
"The liquid in the tube is water  to  which we have  added acid to make it a
conductor and a colouring substance to make it easier to observe. Now watch.
This is the first experiment."
     At the push of a button a faint hum arose as the centrifugal pump began
to drive the pink liquid through the glass coil.
     "The winding  of the  stator  is not  connected with the  mains,"  said
Privalov. "It's only connected with the voltmeter. Watch this!"
     The voltmeter needle  trembled and crept towards the right-hand side of
the dial.
     "See that?"
     "Of course. The liquid is a conductor.  It  cuts the magnetic  lines of
force of the stator and induces electromotive force in the windings. There's
nothing new about that. A meter in which  a liquid passes  through a tube of
non-magnetic material is based on this principle."
     "That's true, there's nothing new about  it. But whereas the voltage in
those meters is insignificant, here-"
     "Oho!" exclaimed Koltukhov,  his eyes  on the voltmeter. "How  did  you
manage that?"
     "Professor  Bagbanly,"  Privalov  said  shortly.  "Now   we'll  do  the
experiment the other way round."
     He switched off the pump. The  liquid stopped moving  and the voltmeter
needle returned to "zero".
     "Now I'll simply send some current into the stator winding."
     He pushed another  button. Although not driven  by  the pump, the  pink
liquid again ran up into the spiral.
     "Let's make it harder." Privalov turned the knob of a valve. "Keep your
eye on  the pressure-gauge.  I could increase  the resistance still more and
get a higher pressure. But the fragility of the glass tubes prevents me from
doing so. Do you see what I'm getting at?"
     Koltukhov looked puzzled. His eyes stared fixedly from beneath his grey
eyebrows.
     "Wait  a   minute,"  he  said.  "In  other  words,  a   liquid   in  an
electromagnetic  field starts  moving all by itself.  Is this a model of the
movement of a liquid through a pipeless pipeline?"
     "Right. The  only  difference is that the surface tension of the liquid
will  take  the place of pipes,  while  a  directed field will  replace  the
windings and magnets."
     "  'The  only  difference' is  a  mild  way of  putting  it," Koltukhov
muttered.
     They  heard  quick  footsteps  in  the  corridor. The  door  opened and
Professor Bakhtiar Bagbanly entered.
     "Ah,  our  main  opponent!" he  said  as  he  shook  hands  with  Pavel
Koltukhov. "Have you come to see for yourself?"
     "He's sceptical," said Privalov.
     "Well, that's part of the scientific approach."  Professor Bagbanly ran
his eyes  over  the apparatus,  then asked Privalov some technical questions
about  the  experiment.  He  began  to  pace  the  room,  a  short,  stocky,
large-headed man with thick grey hair.
     "What examples do we have of mutual penetrability?" he asked suddenly.
     "Diffusion," said Privalov. "The diffusion of solids."
     "Yes, but diffusion calls  for specific conditions.  Even if  you press
perfectly polished surfaces of lead and tin together very hard, it will take
years  before  even the  slightest penetration takes place. However, if  you
heat a  compressed  bundle  of lead and  tin  to  100  degrees  a  layer  of
intermingled molecules will appear in their border area within twelve hours.
What is it  that puts up resistance to transition through the contact zone?"
The  Professor stopped  his pacing  and gave  the two engineers a thoughtful
look. "The surface! That mysterious world of two-dimensional phenomena."
     He  resumed his  pacing, meanwhile  smoothing; with his fingertips, the
grey moustaches beneath his hooked nose.
     "There's another diffusional phenomenon,"  he  went  on, "and  that  is
pressure  contact welding. It produces mutual penetration, but you need high
temperatures and pressures to do it."
     "What  about welding inside  a vacuum?" Privalov asked. "It can be done
at a very low pressure  and without much heating. What is more, you can join
the most diverse materials-steel and glass, for instance. Actually, it isn't
so much welding as intensified diffusion."
     Professor Bagbanly  nodded  in  agreement.  "Yes,  but  why?  Possibly,
because in a  vacuum  a surface is  free  and opens up, as it were, since it
borders on empty space. The forces protecting the surface weaken and open up
the substance. However, our goal is to intensify diffusion until we attain a
state  of  unhindered mutual penetration.  Forcing matter to open its gates,
isn't that so?"  He traced a question mark in  the air with  his forefinger.
"Is there a lot of matter  in solids? The answer is no, there's very little.
Actually, an  atom has  a very insignificant  volume. But  what is  the atom
filled with? After all, matter is concentrated  in the nucleus  of the atom.
From the  standpoint of density, everything  under the sun is as sparse as-"
he searched  for  a comparison-" as  sparse as the hair on the  head  of our
friend Pavel Koltukhov."
     Koltukhov gave a smirk and involuntarily ran a hand over his bald head.
     "Considered from the position of a  mechanical model, matter can easily
be penetrated,"  Professor  Bagbanly went on. "Actually,  though,  we cannot
regard matter as a mechanical conglomeration of small spheres situated at  a
great distance from one another. Powerful  internal forces connect  all  the
components and prevent penetration.  If those  forces  did not exist my hand
would  easily  pass  through metal."  He laid the palm  of his  hand on  the
stator.  "The  probability of  physical particles meeting  is insignificant.
Less probable than peas  colliding  if two handfuls are  thrown towards each
other."
     The Professor wiped his hands on his handkerchief and looked at the two
men, his former pupils, as though expecting them to make some objections.
     "Now I'll formulate the problem," he said, in the same tone of voice he
had once used when lecturing to his students. "Hang your ears on the hook of
attention.  Without  changing the  mechanical structure  of matter  we  must
rearrange its bonds-the bonds  between atoms and between molecules-in such a
manner that they will be completely neutral when they come into contact with
ordinary  matter  during the  period of reciprocal penetration. The internal
bonds must be re-arranged! Then we'll achieve penetrability."
     Koltukhov opened his mouth to make a caustic remark, but just  then the
telephone rang.
     Privalov picked up the receiver. "Hullo. Yes, this is me. Is  that you,
Nikolai?  Now  take  it easy-" He listened for a  moment. "What?!" His  face
changed. "I'll be there in a jiffy." He put down the receiver and glanced at
Professor Bagbanly. "We must all rush off at once!"
     When the blue  draperies were pulled across that  section  of the  room
Valery  realized  that  an uninvited  guest had dropped in.  He put down the
tuning-fork and,  to keep himself busy, examined the  connections.  It was a
good thing he did, for he discovered that one of the weights which regulated
the frequency of the tuning-fork breaker was  loosely attached, and that the
scales on which the mercury heart stood had shifted slightly.
     "From the vibration, no doubt," Valery said to himself. Carefully, with
his little  finger,  he moved the  scales  inside  the Mobius band while  he
adjusted the  weight with his other hand.  At the same moment  guitar chords
sounded on the other side  of the blue draperies and Yura's voice burst into
song.
     "An  old-fashioned tune," Valery reflected  as he continued to move the
scales with his finger. All of a sudden he felt a faint quiver in the little
finger.
     "An electric shock?" he wondered. "No, I haven't touched any metal."
     To be on the safe side, he thrust his little finger into his mouth. How
curious! The  finger did not feel  his mouth, and his mouth did not feel the
finger. He  stared fearfully  at his  finger. It looked perfectly normal. He
put it into his mouth again. But again there was no sensation whatsoever. He
tried biting the tip of the finger. His  teeth came together as though there
was nothing between them.
     Remembering that  there  was a  visitor in the  house, Valery stifled a
scream. "It took an iron will to keep from shouting," he later said. But his
body  gave a jerk  that dislodged  the  mercury heart from  the  scales  and
overturned the tuning-fork breaker.


     Professor Bagbanly,  Boris Privalov and Pavel Koltukhov hurried  up the
stairs and burst breathlessly into Nikolai's flat.
     "Where's Valery?" Privalov demanded.
     Valery, his face  pale  and  covered with sweat, came  into  the  room.
Nikolai excitedly told what had happened.
     Professor Bagbanly touched  Valery's  little  finger. The  tip and  the
joint next to it were penetrable.  The Professor's forefinger passed through
them easily and touched his thumb.
     "Feel anything?" he asked.
     "No," Valery whispered.
     It was easy to establish where the penetrability ended.
     "Light  a  match," said Professor  Bagbanly. "Calm down, young man," he
added when he saw Nikolai nervously break a couple of matches as he tried to
light them. He turned to Valery. "I want you to put  the tip of your  finger
into the flame of Nikolai's match."
     Everyone  held  his breath. Valery  looked as though he were walking in
his sleep. He slowly put his little  finger into  the flame.  It wavered but
its shape did not change. "Do you feel anything?"
     "Yes,"  said Valery  hoarsely,  holding the tip  of  his  finger in the
flame. "My fingertip feels warm."
     The engineers were dumbstruck. They stared in a daze at Valery's little
finger.
     "Thrust your finger into the table," the professor said.
     Valery obeyed. Half of his finger went into the wood.
     "Less goes in now," he  said.  "At first almost the whole  finger  went
in."
     Professor Bagbanly exchanged glances with Privalov.  Then  he set about
examining the apparatus.
     "A  Mobius  band?"  he said.  "Quite an idea.  What did the instruments
register when it happened?"
     "We weren't thinking about penetrability," Yura  explained.  "We wanted
to increase  surface tension, using this mercury heart. Valery must have put
his hands inside the Mobius band a dozen  times without anything  happening.
But when he moved the weight-and I plucked the  strings of  my guitar at the
same time-something clicked. Valery was so scared he  overturned everything,
and so we  don't  know  the exact  readings."  "Automation  experts, humph!"
Koltukhov remarked, looking the silent,  frightened young men  up  and down.
"What's the  idea of this clandestine laboratory? I shudder  to think of the
damage you might have done!"
     "Have you tuned your guitar since then?" Privalov asked.
     "No," said Yura.
     "Then play  exactly  what  you  played  then. We'll  record  it,"  said
Professor Bagbanly. "You have a tape recorder here, don't you?"
     Meanwhile, Valery's little finger was gradually returning to its normal
state. He kept testing it against the table. Finally  only  the very tip  of
the finger went into the wood.  Then, suddenly, he felt his  fingertip being
pinched,  and  with  a cry he pulled his hand away, leaving a bit of skin in
the wood. He immediately thrust his bleeding finger into his mouth. His face
broke into a broad smile. "It's ended!" he shouted.


     The courtyard in Cooper  Lane throbbed  with  music. Strains  of music,
much of it in  a plaintive Oriental  key, poured forth through  all the open
windows from radios, record players and tape recorders.
     Nikolai  had  never  contributed  much  to  the  musical  life  of  the
courtyard, but now he aroused the hostility  of all his  neighbours. Evening
after evening there came  from his windows the same tiresome  strumming of a
guitar, accompanied by the thumping of  a  foot keeping time, and his friend
Yura's voice singing:

     Powder in your pocket to poison me with,
     A locomotive in your pocket to crush me with.

     A detailed description of the installation had been sent to the Academy
of  Sciences in  Moscow, together  with a long memorandum and the tapes. The
young  engineers  had  been  ordered to keep their  mouths  shut and to stop
experimenting at home.
     "You've  done  enough mischief," said Koltukhov.