Galvanized into action, but still confused, the manager gave the orders. A fast motor boat that had been hauled ashore and pot into a shed when the Silver Menace blocked the river was hauled out. A heavy submarine siren was hastily unearthed from one of the workshops, and Davis drove the workmen to the task of fitting a sling on the boat by which the siren could be lowered over the bow. A heavy crane was run up and the motor boat made fast, in readiness to be lifted overboard. Every one worked with the utmost speed of which they were capable. Davis was not his usual good-natured self now. He drove his workmen mercilessly. Hardly had the last of their preparations been completed when a heavy truck rumbled into the yard. Gerrod had commandeered the truck and worked wonders. A grand piano had been lifted bodily into the big automobile. As the truck stopped he was lifting the lid that protected the keys. An electrician stood by the siren, with the tuning apparatus exposed. Hardly had the engine of the truck been shut off when they were busy tuning the blast of the siren to match the tinkling sound of the piano. It took a heart-breakingly long time to get the pitches precisely alike, but then the launch swung high in the air and alighted on the surface of the jelly below. The electrician in the launch pressed the button that would set the siren at work sending out its blast of sound waves through the water. Those on the bank watched in agonized apprehension. The siren sank into the jelly like mass. No audible sound issued from it, once it was submerged, but when the curious sound waves issued into the water from the giant metal plate that in normal times carried warnings to ships at sea a change was visible in the jelly. Where ever the curious water sound traveled the silvery jelly clouded and abruptly turned to liquid! Almost instantly the space between the two wharves, in which the launch lay, was free of the horrible stuff. Gerrod shouted excitedly. Davis swore happily. Nita pushed anxiously forward. "We've got to get to daddy!" she cried desperately. "We mustn't waste a second! Not an instant!"