alone in the larger laboratory when the thing happened. I was in a smaller room, where the balances are, writing up some notes. The thunderstorm had completely upset my work, of course. It was just after one of the louder peals that I thought I heard some glass smash in the other room. I stopped writing, and turned round to listen. For a moment I heard nothing; the hail was playing the devil's tattoo on the corrugated zinc of the roof. Then came another sound, a smash—no doubt of it this time. Something heavy had been knocked off the bench. I jumped up at once and went and opened the door leading into the big laboratory.
I was surprised to hear a queer sort of laugh, and saw Davidson standing unsteadily in the middle of the room, with a dazzled look on his face. My first impression was that he was drunk. He did not notice me. He was clawing out at something invisible a yard in front of his face. He put out his hand, slowly,
