A preposterous gurgle choked up Castlebottom's throat as Bill Petrie and Kitty Carlton disappeared, hand in hand, beyond the square. The _Uvan Thought Clinic_ was housed in a pale amber building. It contained twelve main halls, one dedicated to each of the major sciences. In an outer-reception room, an ancient Uvan whose resin-hard body was rapidly flaking away, fastened a pair of pearl gray eyes on Bill Petrie as he presented his credentials. "Chemistry," said the oldster. "Fuel," answered Bill. The old Uvan led the way to a circular chamber. There, after elaborate preparations, he sat himself on a sort of throne that floated in a bed of pure mercury. Kitty gripped Bill's hand, excitedly. "What's that for?" she asked. "Don't know," Bill replied. "Maybe it insulates him from contact with matter. He can think better in the abstract." The old Uvan nodded and sat rigidly upon the throne. Suddenly the lights dimmed within the chamber, leaving only a suspended glow that was like the infinite apartness and silence of the distant universe. "I am suitable for thought," the old Uvan spoke in a vague tone. "Give me your _equals_." Bill squeezed Kitty's arm, whispering, "I'm going to try something just to see how this works." He faced the Uvan and spoke aloud. "I have two _equals_. The first is something that my Boss needs. The second is for the Fuel Monopoly. Here's the first." Bill handed the Uvan a prepared slip. It asked for a chemical formula which would react on the physical body of Castlebottom in a certain manner, producing a specified result. For a second the Uvan considered the slip, absorbing the requirements. Sudden lights glowed in the segmented grape-cells composing the Uvan's head. The lights shifted from one cell to another, flickering here and there. Abruptly, all the lights went out but a small purplish glow in the grape-cell over the Uvan's right ear. "He's got the answer," Bill whispered. "MgSO_{4},7N_{2}O equals your problem," said the Uvan. "Good!" Bill gasped. "Great Comets, these fellows never miss." "But what's it the formula for?" Kitty asked. "Epsom salts!" "And the second equals?" demanded the vague-voiced Uvan. Bill thrust a second slip forward. The one requiring a formula for synthetic etheroel. Again the lights, blinking like bulbs in a bank of electric lights, hopped from segment to segment in the Uvan's head, feeling around, searching for the cell that contained the correct answer. But now something queer happened. The lights began popping madly in all the cells. They blinked on and off and ran the gamut of colors. Instantly, the old Uvan leaped from his throne, clutched his grape-cluster head and began swearing a blue streak. Bill jerked Kitty to one side, and just in time. The Uvan charged past her, grabbed a hammer and began beating out a wild clangor upon a brass gong near the doorway. "Bill, what is it?" Kitty cried in alarm.