In the wing-room Virdow and Gerald were getting ready for an experiment with flashlight photography. Refusing to be hurried in his scientific investigations, Gerald had insisted that until it had been proven that a living substance could hold a photographic imprint he should not advance to the consideration of Virdow's theory. There must be brain pictures before there could be mind pictures. At least, so he reasoned. None of them knew exactly what his experiment was to be, except that he was going to test the substance that envelopes the body of the bass, the micopterus salmoides of southern waters. That sensitive plate, thinner than art could make it, was not only spoiled by exposure to light, but by light and air combined was absolutely destroyed. And the difficulty of controlling the movements of this fish seemed absolutely insuperable. They could only watch the experimenter. Into a thin glass jar Gerald poured a quantity of powder, which he had carefully compounded during the day. Virdow saw in it the silvery glimmer of magnesium. What the combined element was could not be determined. This compound reached only a third of the distance up the side of the glass. The jar was then stopped with cork pierced by a copper wire that touched the powder, and hermetically sealed with wax. With this under one arm, and a small galvanic battery under the other, and restless with suppressed excitement, Gerald, pointing to a small hooded lantern, whose powerful reflector was lighting one end of the room, bade them follow him. Virdow and Edward obeyed. With a rapid stride Gerald set out across fields, through strips of woodlands and down precipitous slopes until they stood all breathless upon the shore of the little lake. There they found the flat-bottom bateau, and although by this time both Edward and Virdow had begun seriously to doubt the wisdom of blindly following such a character, they resigned themselves to fate and entered.