The Practice Effect by David Brin

he swam over to a ladder, his place on the gunnels was taken by a tall man with a thin fringe of hair. His voice was curiously deep.
    Oh, the wife stays at home, in front of
      The mirror—
    (Ah Wee Hoom?)
    She must think she’s a hat, or a broom,
      Or a door!
    (Ah Hee Hum!)
    Things
practice good, but people
      Are poorer—
    (Ah Wee Hoom?)
    She primps, but still she looks
      Like a who—
    (Ah!
Hee-e-e
Hoom!)
    Dennis smiled weakly, like a person who could tell a pretty good joke was being told but who couldn’t quite understand the punch line.
3
    A small caravan passed slowly through the main gateway into town. There were pedestrians carrying burdens, lined up for inspection at what appeared to be a customs shed. A few men riding shaggy ponies passed through the gateway, not bothered by the guards—apparently officials riding on errands.
    Teams of hulking, rhinoceroslike quadrupeds chuffed patiently outside the gate. Their harnesses led to giant sledges, apparentlyof the kind Dennis had glimpsed that night on the highway.
    Now we’ll see if it’s antigravity after all!
Dennis hurried forward eagerly. The mystery was about to be solved!
    A few of the waiting pedestrians complained desultorily as he edged forward to the cargo sleds, but no one stopped him. His excitement rose as he approached one of the gleaming, high-sided vehicles.
    As he had suspected, there weren’t any wheels at all. The load was strapped to a tilted platform whose four corners ended in little skids. These fitted precisely into the two perfect grooves that ran down every road Dennis had found in Coylia.
    The driver shouted at his beast and snapped the reins. The snuffling, buffalo-like creature strained against its harness, and the sled glided smoothly forward. Dennis followed, crouching for a better look.
    Was it magnetic levitation? Did the tiny runners ride on a cushion of electrical force? There were devices like that on Earth, but nothing anywhere near this compact. The system seemed elegantly simple, yet incredibly sophisticated.
    Dimly, he was aware that people behind him were making ribald remarks about his behavior. There was laughter, and a series of off-color suggestions in the strange local dialect. But Dennis didn’t care. His mind was filled with schematics and raw mathematics as he tested and discarded explanation after explanation for the wonderful sled-and-road combination.
    It was the most fun he had had in weeks!
    A detached part of him realized that he had tipped over into a strange state of mind. The tension of the past two weeks had burst, and the persona best able to cope—the eager scientist—had come to the fore, to the exclusion of almost everything else. For well or ill, it was his way of dealing with too much alienness all at once.
    Dennis got down on all fours and squinted close to the tiny sled in its trough. As the sled moved slowly forward, he let out a small cry of surprise. A clear
liquid
oozed from beneath the little ski as it slid along. The fluid disappeared quickly, seeping almost instantly into the bottom of the trough.
    He touched the bead of wetness that followed the skid, and rubbed the drop between finger and thumb. Almost at once it spread over them in a glossy sheen. He found he couldn’tpress the fingertips together without their slipping aside. They barely even felt each other.
    The fluid was the perfect lubricant! After a moment’s delighted stupefaction, Dennis clawed through one of his thigh pouches for a plastic sampling vial. He had to hold the tube in his left hand, while he vainly tried to wipe his right to get rid of the layer of slipperiness. He pulled the stopper with his teeth.
    Crawling along behind the slowly moving sled, he pushed the vial up behind the ski, catching some of the slippery, elusive fluid. Soon he had twenty-five milliliters or so, almost enough to analyze.…
    His head bumped into the sled as it stopped suddenly. A small rain of