"Very well, sir." Atterbury turned and groped his way through a doorway, and they passed first into what appeared to be a storage-battery room. Huge glass tanks filled with amber-coloured fluid, in which numerous parallel plates were supported, lined the walls from floor to ceiling. An ammeter on the wall caught Bennie's attention. "Weston Direct Reading A. C. Ammeter," he read on the dial. Alternate current! What were they doing with an alternating current in the storage-battery room? His eyes followed the wires along the wall. Yes, they ran to the terminals of the battery. It dawned upon him that there might be something here undreamed of in electrical engineering--a storage battery for an alternating current! The electrician closed a row of switches, brought the two polished brass spheres of the discharger within striking distance, and instantly a blinding current of sparks roared between the terminals. He had been right. This battery not only was charged by an alternating current, but delivered one of high potential. He peered into the cells, racking his brain for an explanation. "Atterbury," said he meditatively, "did I ever tell you why they do that?" "Yes," answered the man. "You--told me--once. The two metals--in the electrolyte--come down--on the plates--in alternate films--as--the current changes direction. But you never told me--what the electrolyte was--I don't suppose--you--would be willing to now, would you?" "H'm," said Bennie, "some time, maybe." But this cue was all that he required. A clever scheme! Pax had formed layers of molecular thickness of two different metals in alternation by the to-and-fro swing of his charging current. When the battery discharged the metals went into solution, each plate becoming alternately positive and negative. He wondered what Pax had used for an electrolyte that enabled him to get a metallic deposit at each electrode. And he wondered also why the metals did not alloy. But it would not do for him to linger too long over a mere detail of equipment. And he turned away to continue his tour of inspection, a tour which occupied most of the morning, and during which he found a well-stocked gallery and made himself a cup of coffee.[5]