The process, he explained, was similar to that employed by Madame Curie in obtaining metallic radium--electrolyzing a radium chloride solution with mercury as a cathode, then driving off the mercury by heat in a current of hydrogen--only he had used the new element instead of radium. "Incidentally, I have learned that this new element is far more radioactive than radium and possesses many curious properties. Among them, it decomposes violently in water--particularly salt water--producing harmless hydrogen and chloride compounds. So we have nothing to fear from those seeds that fell in our oceans, lakes and rivers." "Well, that's something, anyway," said Jim. "But have you found any way to combat the ones that have already hatched?" "Before I answer that question," Professor Wentworth replied, "I shall let you witness a little demonstration." He advanced to the cannon-like device at the other end of the room, swung it on its swivel till it was pointing directly at that fluorescent orange tube on the table. "Watch closely!" he said, throwing a switch. There was a sudden, whining hum in the air and the nib of the big tube glowed a soft, velvety green. Jim gazed at the scene with rapt attention. "Don't look at that one!" whispered Joan. "Look at the other!" Jim did so, and saw that its fluorescence was waning. A moment more the professor held the current on, while the tube grew white. Then he threw off the switch. "Now let us have a look at our captive," he said, striding over. They followed, and one glance told Jim what had happened. That sinister lump of orange metal had vanished. * * * * * But where was it? That was what he wanted to know. "A natural question, but not one easy to answer," was Professor Wentworth's reply. "I shall tell you what I have done; then you may judge for yourself." The cannon-like device which had accompanied the seeming miracle was an adaptation of the cathode tube, whose rays are identical with the beta rays of the atom and consist of a stream of negatively charged particles moving at the velocity of light--186,000 miles a second. These rays, in theory, have the power to combine with the positively charged alpha rays of the atom and drag them from their electrons, causing them to discharge their full quanta of energy at once, in the form of complete disintegration--and it was this theory the professor had acted on. "But, good Lord--that's splitting the atom!" exclaimed Jim. "You don't mean to say you've done that?"