Story, first published: Galaxy Science Fiction, May 1951
A planet-checking expedition comes upon a junkyard of alien equipment, evidence that another race has discovered space travel. In their investigations, they discover to their dismay that they have forgotten how to start the engines of their own spaceship and are marooned on the planet. They find some strange towers containing a creature, part animal and part machine. When they lower a human into the tower, he comes up a crying baby. The creatures are memory traps, which drain off knowledge and send it somewhere to a central receiver in the Galaxy. The crew reverses the "polarity" and knowledge pours out of the trap.
Ewald, Robert J.: When the Fires Burn High and the Wind is from the North, p.61