he old one said, "Stick close by me, child." "What'll it be like, Grandpa?" The youngster was frightened. "Dark, very dark, and big. It moves fast, but we'll keep up with it." The tone was consciously reassuring. "Dark, Grandpa?" "Yes, it sucks heat and absorbs light. You'll find out when you're old and strong enough to swim down to the bottom and see what's there. Now stay with me when we follow it, and don't get lost in the crowd; and don't get ahead of me or get too close to it—you might ta