The "schoolroom" was a large, gray, featureless chamber devoid of blackboard or desk; its only furniture consisted of a number of couches scattered about the floor. Nor were there any teachers; the only adults present were called monitors, and their duties appearaed to be partly those of an usher, and partly those of a nurse, but none pertinent to teaching in any sense of the term Chris had ever encountered. They conducted you to your couch and helped you to fit over your head a bright metal helmet which had inside it what seemed to be hundreds of tiny, extremely sharp points which bit into your scalp just enought to make you nervous, but without enough pressure to break the skin. Once this gadget, which was called a toposcope, was adjusted to their satisfaction, the monitors left, and the room began to fill with the gray gas.

This gas was like a fog, except that it was dry and faintly aromatic... it made it impossible to see the rest of the room until the session was over, when it was sucked out with a subdued roar of blowers...