lengthened, those on board the Advance closed the conning tower. No lights were turned on, as they did not want their movements to be seen, but Tom, his father and Mr. Sharp took their positions near the various machines and apparatus, ready to open the tanks and let the submarine sink to the bottom, as soon as it was possible to do this unobserved.
"Luckily there's no moon," remarked Captain Weston, as he took his place beside Tom. "Once below the surface and we can defy them to find us. It is odd how they traced us, but I suppose that steamer gave them the clue."
It rapidly grew dark, as it always does in the tropics, and when a cautious observation from the conning tower did not disclose the outlines of the other boat, those aboard the Advance rightly concluded that their rivals were unable to see them.
"Send her down, Tom," called his father, and with a hiss the water entered the tanks. The submarine quickly sank below the surface, aided by the deflecting rudder.
But alas for the hopes of the gold-seekers. No sooner was she completely submerged, with the engine started so as to send her out of the lagoon and to the open sea, than the waters all about were made brilliant by the phosphorescent phe-
