“Fritz,
“Only just,” said Fritz. “It was grim. Everything was at least five times as fast as its Terran counterpart and about twenty times as noisy, to say nothing of the heat. If that’s a sample of a deserted Tazoon subway in operation I hope I never have to suffer one during the rush hour.”
“I’ve got news for you,” said Jacko. “We had switching trouble up here on the temporary lines we rigged. According to our calculations we were only able to supply forty-three percent of the total estimated loading. If you’ll hang on for a moment I’ll give you a test run at a hundred percent loading.”
“Don’t bother,” said Fritz hastily. “For that I’d need some repeaters and telemetry equipment plus a few unattended TV cameras. I’m not staying here for a hundred percent loading run.”
“Did you discover anything?”
“Enough. Initially the potential weakness of this system will be confined mainly to its passengers. It’s a Mag-Lev system. The Tazoons were apparently using an adaptation of an A.C. linear motor for traction, with the bottom of the channel as the reactive element. Magnetic repulsion lifts the train clear of the track so that they’re hovering on a magnetic levitation field. I suspect the same principle should be operating on each side to centre the train with respect to the tunnel walls.
“Only we didn’t have enough current to make it fully effective. The trains were grinding on the track and the walls—hence the appalling noise. With the train held in a mechanically frictionless supporting field the only losses to be overcome are inertia, air-resistance and eddy-currents. No wonder this subway is capable of silly speeds!”
Fritz looked about him. “I can’t yet see how the current pickup is arranged, but that’s probably inductive too. Suffice it to say we can soon adapt it to our own purposes.”
“Good.” said Jacko, “But how is this going to produce what we set out to achieve. They asked for a transport system and we’re offering a subway with all that connotes in the way of limited routes and limited points of access. How long do you think that is going to satisfy Nevill?”
“The rest of his career, I should think,” said Fritz. “The building of a subway is a climactic achievement in the history of any culture, requiring, as it does, the co-ordination of a considerable quantity of technological resources. Therefore you only build subways to connect points which are sufficiently important to warrant such endeavour. Give Nevill a functional subway under this city and he will have immediate and convenient access to all those points of the city which the Tazoons
When Fritz arrived at the Staff conference he had the feeling that the rest of the meeting must have been convened about an hour earlier, for the assembly was already engaged in earnest discussion at the time of his arrival. Nevill was leafing forlornly through a formidable pile of notes, reading abstracts, and Colonel Nash was in the chair.
“Ah, Lieutenant, take a seat. We hope you are going to tell us how you came by that impressive source of energy which enabled you to put on that display last evening in the subway.”
“I can do more than that,” said Fritz. “I think I can add considerably to our knowledge of the Tazoons themselves. But let’s start with what were referring to as ‘Harps’. I suddenly realized what they really were.”
“And what was that?”
“Mechano-electric energy converters—piezo-electric generators, if you like. The harps are merely assemblies of high-efficiency piezo-electric crystals operated by the vibrating strings of the harp. The strings are made to vibrate by the passage of those vicious night winds.”
“I’m no scientist,” said Nash, “but I would have thought that piezo-electric effects were scarcely of sufficient magnitude to be useful for energy conversion on that scale.”
“A common misconception,” said Fritz. “Even our relatively undeveloped Terran ferroelectric ceramics are capable of something better than a power generating density of sixteen watts per square centimetre, which has solar cells beaten hollow. The Tazoon crystals are capable of an output of around eighty watts per square centimetre and a conversion efficiency of better than ninety-five percent. An efficiency markedly better than even the most advanced Terran M.H.D. oscillating-plasma reactors, Mechano-electric conversion has always been a highly promising line of development, but hampered by the fact that on Terra there was a scarcity of large-scale sources of mechanical energy of useful frequency.
“The Tazoons made ultra large scale use of medium-level energy by utilizing the winds to activate the harp strings. A Tazoon ‘harp’ in a typical night wind is capable of an output approaching two kilowatts. This comes out to around a megawatt of power for each square kilometre of plain equipped with ‘harps’.”
“Are you sure of this, Fritz?” asked Nevill.
“Perfectly sure. We powered the subway by re-stringing some of the ‘harps’ out on the plains there.”
“But doesn’t the output vary with the force of the wind?”
“Oh yes, but with the harps ranged over a wide area the variations average out fairly well.”
“But how did they obtain their power when there was no wind?”
“They didn’t,” said Fritz. “We’ve found nothing which would indicate any attempt to store the power nor any suggestion of an alternative supply. When the wind stopped, everything stopped. Thus by habit if not by nature the Tazoons were probably nocturnal.”
“But this is ridiculous,” said Nevill. “I still can’t conceive that they would fill whole plains with electrical generating transducers.”
“Why not? They had no particular use for the great outdoors. By and large their native environment was intolerable to them.”
Nevill sat up sharply. “That’s a highly speculative statement to make. How do you arrive at that conclusion?”
“Simple,” said Fritz. “Firstly, they were nearly blind, hence the need for such inordinately intense lighting such as we found on the subway. If my calculation is correct even Tazoo at mid-day was a pretty dull affair to their eyes. Secondly, the temperature the subway reached was so far above ambient that it’s a reasonable guess that they couldn’t tolerate outside temperatures for very long. They had a very low body mass and presumably chilled rapidly.”
“Incredible!” said Nevill. “I knew they were small-boned, but body mass…”
“If you’d seen the rates of acceleration and deceleration of a Tazoon subway train you’d soon see that only creatures of small body mass wouldn’t be injured by it.”
“All right,” said Nash, “you seem to have all the answers. Perhaps you also know why the Tazoons become extinct?”
“I could make a good guess. Even more than ourselves the Tazoons were power dependent animals, for the aforementioned reasons. They had reached a point where they couldn’t exist without power for light and heat, having presumably reached an evolutionary dead-end which had put them out of phase, so to speak, with their native environment. Now remember that they depended on power from the ‘harps’, not having any great resources of alternative fuels, either fossil or nuclear. Remember also that the device frames were made of ironwood from the trees of the forests which used to adorn the plains. I suggest they increased their power generating areas at the expense of the trees until at some point they encountered soil erosion. Normally soil erosion is reversible if the right steps are taken to combat it, but…”
“Well?” said Nash.
“Soil erosion led to sand and the sand and wind conspired to form a sandblast which abraded and destroyed the strings of the harps. The failure of the harps meant loss of power— the very power essential to bring in the desalinated sea-water necessary to help combat the soil erosion. The process developed into a vicious circle—more sand, less ‘harps’; less ‘harps’, more sand, and so on
“When the sand grew deep enough it even prevented ironwood seeds from rooting, so the rest of the forests gradually died also. The Tazoons, faced with a gradual but unalterable loss of power, took the only course open to them—they tried to migrate to the tropical regions where the climate was life-supporting without the need for power. History seems to record that very few of them ever got there, which is not surprising when you consider that the night-wind was certainly capable of blowing a Tazoon clean into the air.”
There was several moments’ silence. “And the ‘harps’?” asked Nash. “That was their
